Abstract: We determined the antimicrobial susceptibilities of 255 clinical isolates of anaerobic bacteria collected in 2007 and 2008 at a tertiary-care hospital in South Korea. Piperacillin-tazobactam, cefoxitin, imipenem, and meropenem were highly active beta-lactam agents against most of the isolates tested. The rates of resistance of Bacteroides fragilis group organisms and anaerobic gram-positive cocci to moxifloxacin were 11 to 18% and 0 to 27%, respectively.
Abstract: Acquired metallo-beta-lactamase (MBL) production is an important mechanism of carbapenem resistance. To our knowledge, carriage of two different MBLs has not been described previously in Acinetobacter spp. We present the characteristics of five Acinetobacter isolates carrying two different MBL genes. The species of all five Acinetobacter isolates with two different MBL genes were Acinetobacter genomospecies 10, and bla(IMP-1), bla(VIM-2) and bla(SIM-1) may coexist in this species. Minimum inhibitory concentrations (MICs) of imipenem for all five isolates with two different MBLs were >or=32 microg/mL, whilst those for two segregants that lost both MBLs were 0.5 microg/mL. The presence of MBL gene-carrying integrons with identical structures suggested the easily transferable nature of the elements, whilst instability of the MBL genes indicated potentially erroneous phenotypic and genetic characterisation.
Abstract: A yeast-like strain was isolated from the brain abscess of a patient diagnosed with astrocytoma. Morphological and molecular analysis on D1/D2 domain in the 26S rRNA gene and internal transcript spacer region of the strain revealed that the strain belonged to the genus Pseudozyma. To the best of our knowledge, this is the first report on the isolation of a Pseudozyma strain from brain abscess.
Abstract: Pseudomonas fulva has not yet been isolated from humans as a pathogen. Herein, we report the first case of P. fulva bacteremia in a patient hospitalized due to trauma. The species was identified using biochemical and molecular genetic analyses of the 16S rRNA, gyrB, rpoB, and rpoD genes.
Abstract: A(-)B(+)Clostridium difficile strains are prevalent in Korea. We performed pulsed-field gel electrophoresis (PFGE), polymerase chain reaction ribotyping, and toxinotyping in 82 A(-)B(+) clinical isolates in Korea. PFGE showed highest discriminatory capability among the 3 methods. By PFGE, persistence of a clone was found, suggesting this clone has adapted to the hospital environment.
Abstract: Susceptibility to several β-lactams and β-lactamase production was investigated in a collection of 20 strains of Pseudomonas otitidis, a new Pseudomonas species that has been recently recognized in association with otic infections in humans. All strains appeared to be susceptible to piperacillin, cefotaxime, ceftazidime and aztreonam, while resistance or decreased susceptibility to carbapenems was occasionally observed. All strains were found to express metallo-β-lactamase (MBL) activity and to carry a new subclass B3 MBL gene, named blaPOM, that appeared to be highly conserved in this species. P. otitidis, therefore, is the first example of a pathogenic Pseudomonas species endowed with a resident MBL. The POM-1 protein from the P. otitidis type strain MCC#10330(T) exhibits the closest similarity (60-64%) to the L1 MBL of Stenotrophomonas maltophilia. Expression in Escherichia coli and Pseudomonas aeruginosa revealed that, similar to L1 and other subclass B3 MBLs, POM-1 confers decreased susceptibility or resistance to carbapenems, penicillins and cephalosporins but not to aztreonam. Expression of the POM MBL in P. otitidis is apparently constitutive and, in most strains, does not confer a carbapenem-resistant phenotype. However, a strong inoculum size effect was observed for carbapenem MICs, and carbapenem-resistant mutants could be readily selected upon exposure to imipenem, suggesting that carbapenem-based regimens should be considered with caution for P. otitidis infections.
Abstract: OBJECTIVES: To examine mutations within the penA, mtrR, porB, ponA and pilQ genes of Neisseria gonorrhoeae to determine their contribution to cephalosporin resistance. METHODS: A total of 46 N. gonorrhoeae isolates with reduced susceptibility to cefixime or ceftriaxone (MICs > or = 0.12 mg/L) and two susceptible isolates were selected. The full sequence of penA and partial sequences previously reported as hot mutation sites of the other genes were analysed. Genotyping by N. gonorrhoeae multiantigen sequence typing (NG-MAST) was also performed. RESULTS: A mosaic penicillin-binding protein 2 (PBP 2) was found in a single isolate that exhibited the highest cefixime MIC (0.5 mg/L). The majority of the isolates with reduced susceptibility to cephalosporins contained non-mosaic PBP 2 sequences, of which PBP 2 pattern XIII was most common (28/46). All isolates with reduced susceptibility to cephalosporins also had mtrR and porB mutations. Two susceptible isolates had the PBP 2 pattern XIV and an incomplete MtrR protein, which was a new mutation. Isolates with identical PBP 2 patterns comprised multiple NG-MAST sequence types. CONCLUSIONS: Reduced susceptibility of N. gonorrhoeae to ceftriaxone and cefixime was associated with diverse penA mutations, particularly PBP 2 pattern XIII containing an Ala-501-->Val substitution, together with mtrR and porB mutations. The existence of only one strain having the mosaic penA sequence indicated that ceftriaxone and cefixime resistance in Korea is mostly not associated with a mosaic penA sequence. Highly heterogeneous NG-MAST sequence types excluded the clonal expansion of a particular subtype.
Abstract: The detection of carbapenemases in Gram-negative bacilli is important for optimal patient treatment and to control spread of the resistance. The modified Hodge test can detect carbapenemase-producing Gram-negative bacilli. In this study, we compared the performance of MacConkey agar and Mueller-Hinton agar for metallo-β-lactamase (MBL) and OXA carbapenemase screening. Overall, the performance of Hodge test was better with MacConkey agar due to enhanced release of β-lactamases from the cells in the presence of bile compounds. Concomitant use of the modified Hodge test could resolve most of the problems with uncertain double-disk synergy tests in MBL detection.
Abstract: This study was performed to determine the mechanisms for acquiring carbapenem resistance in six clinical isolates of Acinetobacter baumannii. All isolates showed similar SmaI-macrorestriction patterns with less than 3 band differences by PFGE. The isolates showed a high level resistance (>32 mg/L) to both imipenem and meropenem by Etest. Phe-Arg-beta-naphthylamide lowered the MICs of carbapenems. Real-time PCR experiments showed that expression levels of the adeB gene in the six A. baumannii isolates were 10- to 40-times higher than those of imipenem-susceptible strains. Direct sequencing of PCR products showed that all isolates carried the bla(OXA-23) gene, which was preceded by ISAba1. The bla(OXA-23) probe hybridized with approximately 500-kb I-CeuI chromosomal fragments, but not with a plasmid. These findings suggest that overexpression of the AdeABC efflux pump as well as chromosome-borne OXA-23 may play a role in acquiring carbapenem resistance in our A. baumannii isolates.
Abstract: We investigated an outbreak caused by carbapenem-resistant Acinetobacter baumannii carrying the blaOXA-23 gene. A novel insertion sequence (IS), named ISAba10, was found to be inserted into the ISAba1 element preceding the blaOXA-23 gene in a group of isolates showing higher carbapenem MICs. The presence of ISAba10 was associated with increased OXA-23 expression, likely by providing additional promoter sequences. ISAba10 was also inserted into the carO outer membrane protein gene in most of these isolates.
Abstract: Resistance of Gram-positive pathogens to first-line antimicrobial agents has been increasing in many parts of the world. We compared the in vitro activities of torezolid with those of other antimicrobial agents, including linezolid, against clinical isolates of major aerobic and anaerobic bacteria. Torezolid had an MIC(90) of ≤0.5 μg/ml for the Gram-positive bacterial isolates tested and was more potent than either linezolid or vancomycin.
Abstract: BACKGROUND: Clostridium difficile is a major cause of antibiotic-associated diarrhea. The objective of this study was to characterize clinical isolates of C. difficile obtained from various regions in Korea with regard to their toxin status, molecular type, and antimicrobial susceptibility. METHODS: We analyzed a total of 408 C. difficile isolates obtained between 2006 and 2008 from 408 patients with diarrhea in 12 South Korean teaching hospitals. C. difficile toxin genes tcdA, tcdB, cdtA, and cdtB were detected by PCR. Molecular genotyping was performed by PCR ribotyping. Antimicrobial susceptibilities of the 120 C. difficile isolates were assessed by agar dilution methods. RESULTS: Among 337 toxigenic isolates, 105 were toxin A-negative and toxin B-positive (A(-)B(+)) and 29 were binary toxin-producing strains. PCR ribotyping showed 50 different ribotype patterns. The 5 most frequently occurring ribotypes comprised 62.0% of all identified ribotypes. No isolate was susceptible to cefoxitin, and all except 1 were susceptible to piperacillin and piperacillin-tazobactam. The resistance rates of isolates to imipenem, cefotetan, moxifloxacin, ampicillin, and clindamycin were 25%, 34%, 42%, 51%, and 60%, respectively. The isolates showed no resistance to metronidazole or vancomycin. CONCLUSIONS: This is the first nationwide study on the toxin status, including PCR ribotyping and antimicrobial resistance, of C. difficile isolates in Korea. The prevalence of A-B+ strains was 25.7%, much higher than that reported from other countries. Binary toxin-producing strains accounted for 7.1% of all strains, which was not rare in Korea. The most prevalent ribotype was ribotype 017, and all A-B+ strains showed this pattern. We did not isolate strains with decreased susceptibility to metronidazole or vancomycin.
Abstract: Objectives To investigate the epidemiological traits of carbapenem-non-susceptible Acinetobacter baumannii (CNSAB) and the usefulness of phylogenetic grouping based on partial rpoB gene sequencing in defining the epidemiological traits of CNSAB. Methods A total of 547 non-duplicate clinical isolates of Acinetobacter spp. were collected from 19 hospitals in Korea in 2008. Detection of genes encoding OXA carbapenemases and metallo-β-lactamases was performed by PCR. The epidemiological relationships of the isolates were investigated by multilocus sequence typing and repetitive-sequence-based PCR. The 450 bp sequence (zone 2) of the rpoB gene was amplified and sequenced. Results Molecular characterization of the 272 CNSAB isolates identified five sequence types (STs): ST92, ST75, ST137, ST138 and ST69. The first four of these STs were clustered into clonal complex (CC) 92, sharing alleles at six of seven housekeeping gene loci; ST69 shared alleles at five of seven loci. CNSAB of CC92 carried the bla(OXA-23) gene (n = 169), the bla(OXA-51)-like gene preceded by ISAba1 (n = 89) or both (n = 14). Notably, all CNSAB isolates carried a G428T substitution in zone 2 of the rpoB gene. Conclusions CNSAB isolates of CC92 with the G428T substitution in zone 2 of the rpoB gene are disseminated nationwide in Korea. A. baumannii with the single nucleotide substitution may be more likely to acquire carbapenem resistance than are other isolates.
Abstract: Purpose: Antimicrobial resistance monitoring could be a useful source of information for treating and controlling nosocomial infections. We analyzed antimicrobial resistance data generated by Korean Hospitals and by a commercial laboratory in 2005 and 2007. Materials and Methods: Susceptibility data for 2005 and 2007 were collected from 37 and 41 hospitals, respectively, and from one commercial laboratory. Intermediate susceptibility was not included in the calculation of resistance rates. Results: Methicillin-resistant Staphylococcus aureus (MRSA) (64%), third-generation cephalosporin-resistant Klebsiella pneumoniae (29%), fluoroquinolone-resistant Escherichia coli (27%), Pseudomonas aeruginosa (33%), and Acinetobacter spp. (48%), and amikacin-resistant P. aeruginosa (19%) and Acinetobacter spp. (37%) were prevalent in hospitals in 2007. A gradual increase of vancomycin-resistant Enterococcus faecium and imipenem-resistant Acinetobacter spp. was observed. Higher incidences of thirdgeneration cephalosporin-resistant E. coli and K. pneumoniae and imipenemresistant P. aeruginosa were found in the commercial laboratory than in the hospitals. Conclusion: Methicillin-resistant S. aureus, third-generation cephalosporin- resistant K. pneumoniae, and fluoroquinolone-resistant E. coli, P. aeruginosa and Acinetobacter spp. remain prevalent in Korea, while the incidence of vancomycin-resistant E. faecium and imipenem-resistant Acinetobacter spp. has increased gradually. The higher prevalences of third-generation cephalosporinresistant E. coli and K. pneumoniae, and imipenem-resistant P. aeruginosa in the commercial laboratory are a new concern.
Abstract: The aim of this study was to investigate the mechanisms involved in the meropenem resistance of Serratia marcescens clinical isolates. Meropenem-resistant (MIC range, 16 to 32 μg/ml) S. marcescens isolates were recovered from nine patients in a tertiary hospital in Seoul, South Korea, from June to November 2005. All the isolates shared identical or similar (>85% similarity) SpeI macrorestriction patterns, indicating clonal spread. PCR experiments did not detect any carbapenemase in those isolates. They carried the bla(CTX-M-22) gene located on a 150-kbp plasmid of the incompatibility group L/M; however, the addition of clavulanic acid exhibited few effects on meropenem MICs. Although meropenem MICs were reduced 4- to 16-fold with the addition of boronic acid, no plasmid-borne AmpC β-lactamase gene was detected in PCR experiments. Real-time quantitative PCR experiments showed that expression levels of the chromosomal ampC gene in those isolates were 87.06 to 155.76 times higher than that of the reference strain ATCC 8100. SDS-PAGE showed a lack of the 42-kDa outer membrane protein (OmpF). In combination with the overproduction of the chromosomal AmpC enzyme, the loss of OmpF may have played a role in the acquisition of meropenem resistance in our isolates.
Abstract: Increase in multidrug-resistant Acinetobacter poses a serious problem in Korea. In this study, 190 imipenem (IPM)-nonsusceptible (NS) Acinetobacter isolates from 12 Korean hospitals in 2007 were used to determine species, prevalence, and antimicrobial susceptibility of OXA carbapenemase- and metallo-β-lactamase (MBL)-producing isolates. bla(OXA-23)-like and ISAba1-asssociated bla(OXA-51)-like genes were detected in 80% and 12% of 178 IPM-NS Acinetobacter baumannii isolates, respectively. A novel bla(OXA-182) was detected in 12 IPM-NS A. baumannii isolates. Twelve out of 14 MBL-producing isolates were non-baumanniiAcinetobacter. A. baumannii isolates with OXA carbapenemase were more often resistant to aminoglycosides, ciprofloxacin, and tigecycline than non-baumannii Acinetobacter isolates with MBL. Identical pulsed- field gel electrophoresis patterns were observed in 89% of A. baumannii isolates with bla(OXA-23)-like gene. In conclusion, extremely rapid increase of IPM-NS A. baumannii in previous Korean studies was mainly due to clonal spread of OXA-23-producing A. baumannii isolates. A novel OXA-182 emerged in Korea.
Abstract: OBJECTIVE: To describe the incidence of recovery of both vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) from culture of a single clinical specimen, to describe the clinical characteristics of patients from whom these specimens were recovered, and to identify the risk factors of these patients. DESIGN: A retrospective cohort and case-control study. SETTING: A tertiary care university hospital and referral center in Seoul, Korea. METHODS: We identified 61 case patients for whom a single clinical specimen yielded both VRE and MRSA on culture, and 122 control patients for whom any clinical specimen yielded only VRE on culture. The control patients were selected by matching 2:1 with the case patients for age, sex, and first date of sampling that led to isolation of VRE or both VRE and MRSA among 1,536 VRE-colonized patients from January 1, 2003, through December 31, 2006. To identify patient risk factors for the recovery of both VRE and MRSA in a single clinical specimen, we performed univariate comparisons between the 2 groups and then multivariate logistic regression analysis. RESULTS: The incidence of recovery of both VRE and MRSA from culture of a single clinical specimen was 3.97% (for 61 of 1,536 VRE-colonized patients) over 4 years. Among these 82 single clinical specimens, the most common type was wound specimens (26.8%), followed by lower respiratory tract specimens (18.3%), urine specimens (17.1%), and catheter tips (15.9%). Of the 61 case patients, 14 (23.0%) had 2 or more single clinical specimens that yielded both VRE and MRSA on culture, and the longest interval from the first sampling that yielded both organisms to the last sampling that yielded both was 174 days. Independent patient risk factors for the presence of both VRE and MRSA in a single clinical specimen were chronic renal disease (odds ratio [OR], 7.00; P=.012 ), urinary catheterization (OR, 3.36; P=.026), and longer total cumulative duration of hospital stay within the previous year (OR, 1.03; P < .001). CONCLUSION: We confirmed that the recovery of VRE and MRSA from a single clinical specimen occurs continually. Because prolonged cell-to-cell contact can facilitate transfer of vanA, close observation and surveillance for vancomycin-resistant S. aureus, especially among patients with risk factors for the recovery of both VRE and MRSA from a single clinical specimen, should be continued.
Abstract: This study was to determine the prevalence and characteristics of CTX-M-type extended-spectrum beta-lactamases (ESBLs) in nonduplicate Escherichia coli (n=760) and Klebsiella pneumoniae (n=379) bloodstream isolates collected during January 2005 to October 2007 at a university hospital (2000 beds) in Seoul, Korea. Antimicrobial susceptibilities were determined by disk diffusion and agar dilution methods. The double-disk synergy test detected ESBLs in 8.7% (66/760) of E. coli and 11.3% (43/379) of K. pneumoniae isolates. Polymerase chain reaction detected bla(CTX-M) in 60/66 (90.9%) E. coli and 9/43 (20.9%) K. pneumoniae isolates with the ESBL phenotype. CTX-M-14 was the most common type of CTX-M ESBLs in both E. coli (n=32) and K. pneumoniae (n=6). CTX-M-15 was the 2nd most common type of CTX-M ESBLs in E. coli (n=22), but it was not detected in K. pneumoniae. In addition, CTX-M-24 (n=2), CTX-M-65 (n=2), CTX-M-27 (n=1), and CTX-M-32 (n=1) were detected for the 1st time in Korea.
Abstract: OBJECTIVES: This study evaluated the effects of antimicrobial treatment against vancomycin-resistant enterococci (VRE) and delayed administration of anti-VRE therapy on mortality, and determined independent risk factors for delayed all-cause mortality of VRE bacteremia patients. METHODS: Over 10 years, 153 patients with clinically significant monomicrobial VRE bacteremia were identified among a total of 2834 patients in a VRE cohort. The main outcomes were immediate (7-day) and delayed (28-day, 60-day) all-cause mortality. RESULTS: The 7-day (P<0.001) and 28-day (P=0.041) mortalities were lower in the group receiving anti-VRE therapy, but the 60-day mortality (P=0.113) was unaffected. The mortalities of patients receiving anti-VRE therapy later than 72h after the onset of bacteremia were no different from that of patients receiving treatment within 72h. Both a higher APACHE II score (hazard ratio [HR], 1.10; P<0.001 and HR, 1.12; P<0.001, respectively) and the presence of septic shock at the onset of bacteremia (HR, 1.91; P=0.047 and HR, 1.78; P=0.034, respectively) were independent risk factors for 28-day and 60-day mortality. CONCLUSION: These findings suggest that in spite of antibiotic therapy against VRE, patients with VRE bacteremia eventually have a higher risk of death because of severe illness at the onset of bacteremia.
Abstract: Carbapenem-resistant Acinetobacter spp. are being increasingly reported worldwide, including in South Korea, where we examined 144 representative isolates collected in a nationwide hospital survey in 2005. Metallo-beta-lactamases were detected in only 19.4% of isolates, none of which were Acinetobacter baumannii, whereas 74.3% of isolates (mostly A. baumannii) expressed bla(OXA) carbapenemase genes. Among the latter, 47 had bla(OXA-23)-like genes and 56 had upregulated bla(OXA-51)-like variants, including bla(OXA-66), (-83), (-109) and (-115); bla(OXA-115) was a novel variant, detected in two isolates. bla(OXA-72) (bla(OXA-40)-like) was detected in only a single Acinetobacter baylyi isolate, whilst three Acinetobacter calcoaceticus isolates had both bla(VIM-2)-like and bla(OXA-58) genes. Pulsed-field gel electrophoresis (PFGE) suggested the spread of A. baumannii clones with OXA carbapenemases within and between hospitals. In conclusion, the recent increase in imipenem-resistant Acinetobacter spp. from South Korea is mostly due to OXA-type carbapenemases.
Abstract: PURPOSE: Two Korean nationwide studies showed that metallo-beta-lactamases (MBLs)-producing-Pseudomonas spp. are not rare. The aim of this study was to assess the trends of MBL-producing isolates among imipenem-resistant isolates of Pseudomonas spp. MATERIALS AND METHODS: Imipenem-resistant clinical isolates were collected from 23 hospitals and one commercial laboratory participating in the KONSAR program in 2005. Polymerase chain reaction (PCR) was used to detect MBL genes. RESULTS: Alleles of MBL genes were detected in 10.8% of 415 Pseudomonas aeruginosa and 66.7% of 12 P. putida isolates from 18 of 24 hospitals/laboratory. Among the 14 IMP-1-like and 39 VIM-2-like MBLs, emergence of IMP-6 was detected for the first time. CONCLUSION: Prevalence of MBL-producing P. aeruginosa has not significantly increased, but IMP-6 emerged in P. aeruginosa.
Abstract: BACKGROUND/AIMS: Risk factors for mortality resulting from anaerobic infection are incompletely defined. The clinical significance of a broad range of pathogenic obligate anaerobic organisms was examined, and factors independently associated with mortality were identified in patients with clinically significant anaerobic infections. METHODS: The medical records of 1,050 patients with anaerobic infections were retrospectively reviewed at Severance Hospital in Seoul, Korea. RESULTS: The mean age of the patients was 54.1+/-16.8 years, and 57.7% were men. Overall, 320 (30.5%) patients with case-defined illness experienced pain at the affected site, and 230 (21.9%) experienced pus flow from lesions. Ten (1.4%) patients presented with shock, and 80.3% of the clinically significant cases were polymicrobial anaerobic infections. The mean number of pathogens, including aerobic and anaerobic bacteria, was 3.7+/-1.0 (minimum 1, maximum 5), and the number of anaerobic organisms was 1.0+/-0.3 in each specimen. The major pathogens by rank were the Bacteroides fragilis group, which accounted for 41.8% of anaerobic infections, followed by Clostridium spp. (11.8%), Prevotella spp. (9.4%), and Peptostreptococcus spp. (8.4%). Escherichia coli (17.5%), Staphylococcus aureus (7.5%), and Klebsiella pneumoniae (7.5%) were common concomitant aerobic organisms. The overall crude mortality rate resulting from anaerobic infection was 29.7%. Among the determining factors associated with mortality, liver disease (p=0.003) and old age (p=0.005) were significant in multivariate analysis. CONCLUSIONS: Anaerobic infection is polymicrobial and has a significant role in morbidity and mortality. Underlying liver disease was associated with poor prognosis in anaerobic infection.
Abstract: A Swedish patient of Indian origin traveled to New Delhi, India, and acquired a urinary tract infection caused by a carbapenem-resistant Klebsiella pneumoniae strain that typed to the sequence type 14 complex. The isolate, Klebsiella pneumoniae 05-506, was shown to possess a metallo-beta-lactamase (MBL) but was negative for previously known MBL genes. Gene libraries and amplification of class 1 integrons revealed three resistance-conferring regions; the first contained bla(CMY-4) flanked by ISEcP1 and blc. The second region of 4.8 kb contained a complex class 1 integron with the gene cassettes arr-2, a new erythromycin esterase gene; ereC; aadA1; and cmlA7. An intact ISCR1 element was shown to be downstream from the qac/sul genes. The third region consisted of a new MBL gene, designated bla(NDM-1), flanked on one side by K. pneumoniae DNA and a truncated IS26 element on its other side. The last two regions lie adjacent to one another, and all three regions are found on a 180-kb region that is easily transferable to recipient strains and that confers resistance to all antibiotics except fluoroquinolones and colistin. NDM-1 shares very little identity with other MBLs, with the most similar MBLs being VIM-1/VIM-2, with which it has only 32.4% identity. As well as possessing unique residues near the active site, NDM-1 also has an additional insert between positions 162 and 166 not present in other MBLs. NDM-1 has a molecular mass of 28 kDa, is monomeric, and can hydrolyze all beta-lactams except aztreonam. Compared to VIM-2, NDM-1 displays tighter binding to most cephalosporins, in particular, cefuroxime, cefotaxime, and cephalothin (cefalotin), and also to the penicillins. NDM-1 does not bind to the carbapenems as tightly as IMP-1 or VIM-2 and turns over the carbapenems at a rate similar to that of VIM-2. In addition to K. pneumoniae 05-506, bla(NDM-1) was found on a 140-kb plasmid in an Escherichia coli strain isolated from the patient's feces, inferring the possibility of in vivo conjugation. The broad resistance carried on these plasmids is a further worrying development for India, which already has high levels of antibiotic resistance.
Abstract: BACKGROUND: This study was performed to investigate the prevalence of qnr genes in clinical isolates of Escherichia coli from Korea that produce extended-spectrum beta-lactamases (ESBLs). METHODS: During the period of May to June 2005, we collected clinical isolates of E. coli that were intermediate or resistant to ceftazidime and/or cefotaxime from 11 Korean hospitals. Antimicrobial susceptibility was determined by the disk diffusion and agar dilution methods. ESBL production was confirmed phenotypically by the double-disk synergy test. ESBL and qnr genes were searched for by PCR amplification, and the PCR products were then subjected to direct sequencing. RESULTS: Double-disk synergy tests were positive in 84.3% (118/140) of ceftazidime- and/or cefotaxime-nonsusceptible E. coli isolates. The most prevalent types of ESBL in E. coli isolates were CTX-M-14 (N=41) and CTX-M-15 (N=58). Other ESBLs were also identified, including CTX-M-3 (N=7), CTX-M-9 (N=8), CTX-M-12 (N=1), CTX-M-57 (N=1), SHV-2a (N=2), SHV-12 (N=17) and TEM-52 (N=4). The qnrA1 and qnrB4 genes were identified in 4 and 7 ESBL-producing isolates, respectively. CONCLUSIONS: CTX-M-type enzymes were the most common type of ESBL in E. coli isolates from Korea, and the qnr genes were not uncommon in ESBL-producing E. coli isolates. Dissemination of E. coli containing both ESBL and qnr genes could compromise the future usefulness of the expanded-spectrum antibiotics for the treatment of infections.
Abstract: The spread of Gram-negative bacilli with acquired metallo-beta-lactamase (MBL) threatens the successful treatment of major nosocomial infections. The objective of this study was to evaluate the differences in the clinical characteristics of bacteremia caused by MBL-producing Acinetobacter species and MBL non-producing isolates. Two retrospective case-control studies were conducted using data on patients with Acinetobacter bacteremia, who were admitted between January 2001 and December 2005 at a 1500-bed, tertiary-care teaching hospital. Case group 1 (n=27) included patients from whom imipenem-resistant Acinetobacter was isolated in blood culture, and case group 2 (n=7) consisted of those patients from group 1 who yielded MBL-producing isolates. The control group (n=41) included patients from whom carbapenem-susceptible Acinetobacter isolates were isolated in blood culture. Multivariate analysis revealed that the independent risk factors for imipenem-resistant Acinetobacter bacteremia were neutropenia and prolonged use of carbapenem. The independent risk factors for MBL-producing Acinetobacter bacteremia were neutropenia and prolonged use of cephalosporins. The results of this study suggest that a prolonged use of cephalosporins may be associated with MBL-producing Acinetobacter bacteremia.
Abstract: We report a case of necrotizing fasciitis involving Streptococcus agalactiae, Arcanobacterium haemolyticum, and Finegoldia magna in a 36-yr-old female diabetic patient, which started after a minor dog bite to the toe of the patient. This case suggested that a trivial infection after a minor dog bite in an immunocompromised patient such as diabetes patient could result in a significant complication such as necrotizing fasciitis. The life-threatening infection was cured by timely above-the-knee amputation, as well as penicillin G and clindamycin therapy.
Abstract: Of 462 Korean Clostridium difficile isolates, 77.5% were toxin B positive but 21.4% were toxin A negative (A(-) B(+)). The binary toxin gene was detected in nine isolates. A higher fluoroquinolone resistance of A(-) B(+) strains may contribute to the increase of these strains. Toxin A detection alone may underdiagnose C. difficile-associated disease.
Abstract: The in vitro activities of CG400549, a novel FabI inhibitor, were compared to those of linezolid and commonly used antimicrobials against recent bacterial isolates. CG400549 had an MIC(90) of 0.5 microg/ml for Staphylococcus aureus strains and was more potent than either linezolid or vancomycin.
Abstract: We investigated the resistance mechanisms and clonality among 42 imipenem-non-susceptible Klebsiella pneumoniae isolated at a tertiary care hospital in Korea. Two isolates had bla(VIM-2) alleles, whereas bla(CMY-2)- and bla(DHA-1)-like alleles were detected in 24 and 16 isolates, respectively, with these enzymes confirmed by sequencing for representative isolates. Transfer of bla(CMY-2) and bla(DHA-1) was achieved by conjugation. Addition of 300 mg/L 3-aminophenylboronic acid (APB) reduced the minimum inhibitory concentration for 90% of the organisms (MIC(90)) of imipenem and meropenem eight- and four-fold, respectively, for the bla(CMY-2)- and bla(DHA-1)-positive isolates, confirming the role of these enzymes in resistance. SDS-PAGE of outer membrane proteins for representative isolates showed lack or greatly diminished expression of OmpK35 and OmpK36 porins. Pulsed-field gel electrophoresis of XbaI-restricted genomic DNA revealed two closely related clusters among 23 bla(CMY-2)-positive isolates, whereas those with bla(DHA-1) were more heterogeneous. In conclusion, reduced imipenem susceptibility among K. pneumoniae at this Korean hospital was largely co-mediated by production of plasmid-mediated AmpC beta-lactamases along with lack or greatly diminished expression of OmpK35 and OmpK36 porins.
Abstract: PURPOSE: Virulent gene expression in Staphylococcus aureus is controlled by regulators such as the accessory gene regulator (agr). Strains can be divided into four major agr groups (agr I-IV) on the basis of agrD and agrC polymorphisms. The purpose of this study was to define the proportion of agr I, II, and III polymorphisms and to compare the clinical characteristics between group I and non-group I polymorphisms of methicillin-resistant Staphylococcus aureus (MRSA) strains in a Korean tertiary care teaching hospital. MATERIALS AND METHODS: A total of 158 clinical isolates were evaluated by RFLPs (restriction fragment length polymorphisms). RESULTS: The mean age of the patients was 50.2 +/- 21.9 years old. There were 74 (49.3%), 66 (44.0%), 10 (6.7%), 7 (4.4%), and 1 (0.6%) strains in agr group I, II, III, I + II, and I + III polymorphisms, respectively. Only ear infections were a statistically significant clinical parameter according to univariate (p=0.001) and multivariate analysis (OR, 4.721 (1.273-17.508), p=0.020). CONCLUSION: This study suggests that agr group I is the most prevalent in Korea, and ear infections are correlated with the group I polymorphism, which is a different clinical trend from western countries. It can also be inferred that community-acquired MRSA correlates with agr group I.
Abstract: BACKGROUND: Blood culture is important for the determination of the etiologic agent of bacteremia. Analysis of blood culture results and antimicrobial susceptibility trend can provide clinicians with relevant information for the empirical treatment of patients. METHODS: The species and antimicrobial susceptibility of the isolates from blood cultures at the Severance Hospital during 1994-2003 were analysed. Blood specimens were cultured for 7 days using tryptic soy broth and thioglycollate medium. Identification of organism was based on conventional methods or commercial kit systems. Antimicrobial susceptibility was tested by a disk diffusion method. RESULTS: Of 536,916 blood specimens cultured, 24,877 (4.6%) from 13,102 patients were positive. Among the isolates, 93.1% were aerobic or facultative anaerobic bacteria, 3.3% anaerobes, and 3.6% fungi. Escherichia coli was isolated most frequently, followed by Staphylococcus aureus, alpha-hemolytic Streptococcus, Enterococcus spp., and Klebsiella pneumoniae. The proportion of patients with Enterococcus faecium and K. pneumoniae gradually increased during this study. Enterococcus, S. aureus and alpha-hemolytic Streptococcus were frequently isolated from the age group of less than 2 yr. E. coli, Enterococcus spp., K. pneumoniae and S. aureus from the age group of over 50 yr. Oxacillin-resistant S. aureus decreased, whereas vancomycin-resistant E. faecium and imipenemresistant Pseudomonas aeruginosa and Acinetobacter baumannii increased. CONCLUSIONS: E. coli was the most common cause of bacteremia and S. aureus, alpha-hemolytic Streptococcus, and K. pneumoniae were frequently isolated pathogens. The bacteremia due to Enterococcus, K. pneumoniae, fungi, vancomycin-resistant E. faecium, and imipenem-resistant P. aeruginosa and A. baumannii gradually increased during this period.
Abstract: BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) and some gram-negative bacilli are very prevalent nosocomial pathogens, commonly causing mixed infections, and are often resistant to multiple drugs. Arbekacin is an aminoglycoside used for the treatment of MRSA infections, but is also active against some gram-negative bacilli. The aim of this study was to determine in vitro activity of arbekacin against recent clinical isolates of staphylococci and gram-negative bacilli. Materials and METHODS: The strains were isolated from clinical specimens of patients at Severance Hospital in 2003. Antimicrobial susceptibility was tested by the Clinical and Laboratory Standards Institute agar dilution method. The following arbekacin breakpoints were used: susceptible, </=4 microg/mL; and resistant, >/=16 microg/mL . RESULTS: All isolates of staphylococci tested were inhibited by </=4 microg/mL of arbekacin, regardless of their methicillin susceptibility. The MIC90s of arbekacin, 1-4 microg/mL, were 8->32-fold and >32-128-fold lower than those of amikacin and gentamicin, respectively. The resistance rates of MRSA, methicillin-susceptible S. aureus, methicillin-resistant coagulase-negative staphylococci (CNS) and methicillin-susceptible CNS were 0% to arbekacin, 0-54% to amikacin, and 24-79% to gentamicin. The MIC90s of arbekacin for Escherichia coli and Citrobacter freundii, 1 microg/mL and 16 microg/mL, were 2-4-fold and 8-16-fold lower than those of amikacin and gentamicin, respectively. However, The MIC90s of arbekacin for other species of gram-negative bacilli, 64->128 microg/mL, were similar to those of other aminoglycosides. CONCLUSIONS: Arbekacin may be a useful alternative to glycopeptides for the treatment of monomicrobial methicillin-resistant staphylococcal infections, as well as mixed infections with gram-negative bacilli, as most isolates of E. coli, C. freundii and some other gram-negative bacilli were also susceptible to arbekacin.
Abstract: BACKGROUND: Cinical and Laboratory Standards Institute (CLSI) recommends the use of cefoxitin disks instead of long-used oxacillin disks for screening methicillin-resistant isolates of staphylococci. The frequency of discrepant results and accuracy of the tests were evaluated by detecting mecA gene. METHODS: A total of 3,123 Stapylococci isolates from patients in Severance Hospital were tested during September 2005 to August 2006 by the CLSI-recommended test using both cefoxitin and oxacillin disks. The mecA gene was detected by PCR and the oxacillin minimum inhibitory concentration (MIC) was determined by using agar dilution method for the isolates with discrepant tests. RESULTS: Among 1,915 S. aureus islolates tested, one isolate was resistant to oxacillin disk but susceptible to cefoxitin disk; the isolate did not have mecA gene. Another isolate susceptible to oxacillin but resistant to cefoxitin had mecA gene. Among 1,208 coagulase-negative staphylococcal isolates, 15 isolates were resistant to oxacillin disk but susceptible to cefoxitin disk; the isolates did not have mecA genes. Two isolates susceptible to oxacillin disk but resistant to cefoxitin disk had mecA genes. Among the 16 Staphylococcus isolates that did not have mecA gene, 15 isolates had the oxacillin MICs of </= 2 microg/mL and were considered as methicillin-susceptible, while 1 isolate with the MIC of 4 microg/mL was considered as methicillin-resistant. CONCLUSIONS: Overall, 1.9% of staphylococcal isolates showed discrepant results when the screening tests were performed by using oxacillin and cefoxitin disks. None of the isolates resistant to oxacillin disk but susceptible to cefoxitin disk had mecA gene. In conclusion, the cefoxitin disk test is more reliable than oxacillin disk test in screening methicillin-resistant staphylococcal isolates.
Abstract: Monitoring temporal trends of antimicrobial resistance can provide useful information for the empirical selection of antimicrobial agents to treat infected patients and for the control of nosocomial infections. In this study, we analyzed antimicrobial resistance of clinically relevant bacteria in 2003 at Korean hospitals and at a commercial laboratory. The following organism-antimicrobial agent resistance combinations were very prevalent: oxacillin-resistant Staphylococcus aureus (68%), expanded-spectrum cephalosporin-resistant Klebsiella pneumoniae (25%), and fluoroquinolone-resistant Escherichia coli (33%), Acinetobacter spp. (58%), and Pseudomonas aeruginosa (40%). Moreover, gradual increases in vancomycin-resistant Enterococcus faecium (20%), cefoxitin-resistant E. coli (10%) and K. pneumoniae (23%), and imipenem-resistant P. aeruginosa (20%) and Acinetobacter spp. (13%) were also observed. The resistance rates of Acinetobacter spp. to most antimicrobial agents at hospitals and at the commercial laboratory were similar. Among the Acinetobacter spp. isolated at a tertiary-care hospital, 46.2% were multidrug-resistant to 9-12 of 13 antimicrobial agents, and 18.3% were panresistant. The exclusion of duplicate isolates at a tertiary-care hospital significantly lowered the proportion of oxacillin-resistant S. aureus, vancomycin-resistant E. faecium, and fluoroquinolone-resistant E. coli.
Abstract: CTX-M-14- and -2-like extended-spectrum beta-lactamases were detected in 5 and 1 Proteus mirabilis isolates, respectively, among 92 non-duplicate strains tested from December 2002 to September 2003. This is the first report of the CTX-M-14 enzyme in P. mirabilis to the best of our knowledge and suggests that the CTX-M-type enzyme is gradually spreading to this species. bla(TEM), bla(SHV-1), and/or bla(OXA-10) alleles were also detected in 35 ampicillin-resistant isolates tested.
Abstract: Multiple antibiotic resistance threatens successful treatment of Acinetobacter baumannii infections worldwide. Increasing interest in the well-known activity of sulbactam against the genus Acinetobacter has been aroused. The purpose of this study was to compare the outcomes for patients with Acinetobacter bacteremia treated with cefoperazone/sulbactam versus imipenem/cilastatin. Forty-seven patients with Acinetobacter baumannii bacteremia were analyzed through a retrospective review of their medical records for antibiotic therapy and clinical outcome. Thirty-five patients were treated with cefoperazone/sulbactam, and twelve patients with imipenem/cilastatin. The percentage of favorable response after 72 hours was not statistically different between cefoperazone/sulbactam group and imipenem/cilastatin group. The mortality rate was not statistically different, too. Cefoperazone/sulbactam was found to be as useful as imipenem/cilastatin for treating patients with Acinetobacter bacteremia.
Abstract: Cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae are relatively prevalent in Korea, suggesting dissemination of plasmid-mediated AmpC beta-lactamases. In this study, 238 isolates of cefoxitin-resistant E. coli and K. pneumoniae (not including subspecies ozaenae and rhinoscleromatis) were collected in 2003 from 16 Korean hospitals. The prevalence of plasmid-mediated AmpC beta-lactamases was determined by PCR. The AmpC gene alleles detected in E. coli and K. pneumoniae were bla(DHA-1), 10 (8.6%) and 93 (76.2%); bla(CMY-1)-like, 14 (12.1%) and 2 (1.6%); and bla(CMY-2)-like, 38 (32.7%) and 1 (0.8%) isolates, respectively. The genes identified were bla(DHA-1), bla(CMY10)-like, and bla(CMY-2)-like, and a new variant, bla(CMY-18). Plasmidmediated AmpC gene allele-positive isolates were present both in large city and in small province hospitals, as well as in isolates from outpatients. The proportions of plasmid-mediated AmpC gene-positive isolates were similar in both expanded spectrum beta-lactamase (ESBL)-producing and -nonproducing isolates. In conclusion, DHA-1, CMY-2-like, and CMY-10-like plasmid-mediated AmpC beta-lactamase-producing K. pneumoniae and E. coli isolates are widely disseminated in both large city and small province hospitals. Absence of bla(CMY-1) and detection of a novel variant of bla(CMY-2), bla(CMY-18), indicate continued evolution of the prototype genes. Similar proportions of plasmid-mediated AmpC gene-positive isolates in both ESBL-producing and -nonproducing isolates suggest unhindered future spread of these resistances.
Abstract: A 40-year-old man who had been treated for multiple myeloma, complained of decreased visual acuity of the left eye on the 30th day of admission. The nucleotide sequences of a fungal PCR product from vitreous fluid showed 99% homology with Aspergillus fumigatus (AY373851). Aspergillus spp. was isolated from vitreous fluid culture, also. Rapid diagnosis and intervention are critical elements for the Aspergillus endophthalmitis; therefore, it would be helpful to combine the fungal PCR with conventional fungus culture for clinically indicated specimens.
Abstract: A nationwide antimicrobial resistance surveillance has been conducted since 1997 in Korea. In this study, susceptibility test data generated in 2004 by KONSAR group hospitals were analyzed and compared to those at a commercial laboratory. In hospitals, the rank orders of organisms in 2004 were identical to those in 2003. The most prevalent species was Staphylococcus aureus (20.2%) in hospitals, but Escherichia coli (29.7%) in the commercial laboratory. The proportions of Enterococcus faecium to all isolates of Enterococcus faecalis plus E. faecium were 47.2% in hospitals and 24.9% in the commercial laboratory. The mean resistance rates of significant antimicrobial-organism combinations in hospitals were: oxacillin-resistant S. aureus (68%), oxacillin-resistant (penicillin- nonsusceptible) Streptococcus pneumoniae (68%), vancomycin-resistant E. faecium (25%), cefotaxime-resistant E. coli (14%), ceftazidime- and cefoxitin-resistant Klebsiella pneumoniae (34% and 32%, respectively), and imipenem-resistant Acinetobacter spp. and Pseudomonas aeruginosa (17% and 24%, respectively). In conclusion, oxacillin-resistant staphylococci, expanded-spectrum cephalosporin-resistant K. pneumoniae, and imipenem-resistant Acinetobacter spp. and P. aeruginosa were prevalent in 2004. Increasing trends were observed for vancomycin-resistant E. faecium, cefoxitin- resistant E. coli and K. pneumoniae, and imipenem-resistant Acinetobacter spp. and P. aeruginosa. Certain antimicrobial- organism combinations were also prevalent among the commercial laboratory-tested strains.
Abstract: Among imipenem-nonsusceptible isolates, acquired metallo-beta-lactamase genes were detected in 36 of 581 (6.2%) Pseudomonas aeruginosa isolates, 42 of 44 (95.4%) other Pseudomonas species, and 136 of 513 (26.5%) Acinetobacter species from 2003 to 2004 at a Korean hospital. Overall, bla(VIM-2)-like genes were the most prevalent and were also detected in Enterobacteriaceae, including Klebsiella pneumoniae.
Abstract: The aim of the study was to investigate the phenotypic and genetic characteristics of recently emerging cefoxitin-resistant and induction-positive isolates of Escherichia coli, Klebsiella species, and Proteus mirabilis. Strains of Enterobacteriaceae were isolated at a Korean tertiary care hospital between June and December 2002. Induction was tested using cefoxitin and aztreonam disks, the blaDHA allele was detected by PCR, and pulsed-field gel electrophoresis (PFGE) patterns were also analyzed. Among the cefoxitin-resistant isolates, 2.7% of E. coli, 21.1% of Klebsiella pneumoniae, 32.0% of Klebsiella oxytoca, and 8.3% of P. mirabilis isolates showed induction, and were blaDHA-1 allele positive. To the best of our knowledge, this is the first report of blaDHA-1 in P. mirabilis. The MICs of ceftazidime, cefotaxime, and aztreonam increased significantly by higher inoculum, suggesting that their clinical usefulness is limited. Presence of multiple PFGE patterns and identical patterns in some isolates suggest that the widely disseminated blaDHA-1 in Klebsiella species was because of both horizontal and clonal spread.
Abstract: We investigated an outbreak of Acinetobacter baumannii in an intensive care unit and in the surgery, medicine, neurology, and urology wards of the Kosin University Gospel Hospital in Busan, Korea. The outbreak involved 36 cases of infection by A. baumannii producing the OXA-23 beta-lactamase over an 8-month period and was caused by a single pulsed-field gel electrophoresis clone. The epidemic isolates were characterized by a modified cloverleaf synergy test. Isoelectric focusing of crude bacterial extracts detected one nitrocefin-positive band with a pI value of 6.65. PCR amplification and characterization of the amplicons by direct sequencing indicated that the epidemic isolates carried a bla(OXA-23) determinant. The epidemic isolates were characterized by a multidrug resistance phenotype that remained unchanged over the outbreak, including penicillins, cephamycins, extended-spectrum cephalosporins, carbapenems, monobactams, and aminoglycosides. This study shows that the bla(OXA-23) resistance determinant may become an emerging therapeutic problem.
Abstract: CTX-M-14-type extended-spectrum beta-lactamase was first detected in Salmonella enterica serovar London strains which were isolated from three hospitalized pediatric patients with gastroenteritis. The isolates had pulsed-field gel electrophoresis patterns identical to those of the previously isolated antimicrobial-susceptible strains from community-acquired gastroenteritis, suggesting the susceptible clone acquired the resistance.
Abstract: The Etest MBL (AB BIODISK, Solna, Sweden) correctly differentiated all 57 isolates of Acinetobacter spp. and Pseudomonas aeruginosa with the bla(IMP-1) allele and 135 of 137 (98.5%) Acinetobacter spp. and Pseudomonas spp. isolates with the bla(VIM-2) allele. The Etest MBL was reliable for detecting the IMP-1- and VIM-2-producing Pseudomonas and Acinetobacter isolates.
Abstract: Carbapenem resistance mediated by acquired carbapenemase genes has been increasingly reported, particularly for clinical isolates of Pseudomonas aeruginosa and Acinetobacter spp. Of 1,234 non-duplicate isolates of carbapenem-resistant Pseudomonas spp. and Acinetobacter spp. isolated at a tertiary-care hospital in Seoul, Korea, 211 (17%) were positive for metallo-beta-lactamase (MBL). Of these, 204 (96%) had either the bla(IMP-1) or bla(VIM-2) allele. In addition, seven Acinetobacter baumannii isolates were found to have a novel MBL gene, which was designated bla(SIM-1). The SIM-1 protein has a pI of 7.2, is a new member of subclass B1, and exhibits 64 to 69% identity with the IMP-type MBLs, which are its closest relatives. All SIM-1-producing isolates exhibited relatively low imipenem and meropenem MICs (8 to 16 microg/ml) and had a multidrug resistance phenotype. Expression of the cloned bla(SIM-1) gene in Escherichia coli revealed that the encoded enzyme is capable of hydrolyzing a broad array of beta-lactams, including penicillins, narrow- to expanded-spectrum cephalosporins, and carbapenems. The bla(SIM-1) gene was carried on a gene cassette inserted into a class 1 integron, which included three additional cassettes (arr-3, catB3, and aadA1). The strains were isolated from sputum and urine specimens from patients with pneumonia and urinary tract infections, respectively. All patients had various underlying diseases. Pulsed-field gel electrophoresis of SmaI-digested genomic DNAs showed that the strains belonged to two different clonal lineages, indicating that horizontal transfer of this gene had occurred and suggesting the possibility of further spread of resistance in the future.
Abstract: Respiratory isolates of Klebsiella pneumoniae in Korea during 2002-2003 were studied to determine the prevalence and types of extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated AmpC beta-lactamases (PABLs). ESBL-production was tested by double-disk synergy, and genotypes of beta-lactamases were determined by PCR and sequencing. ESBLs were detected in 28.4% of 373 isolates, and the most prevalent types were SHV-12 (63 isolates) and CTX-M-14 (9 isolates). Forty of 75 ESBL-producers (53.5%) also had PABLs: 21 isolates with CMY-2-like, 17 with DHA-1-like. Pulsed-field gel electrophoresis showed 19 types and 25 of 74 isolates had an identical pattern, indicating nosocomial spread. Dissemination of ESBL- and PABL-producing K. pneumoniae strains in Korea is a particular concern, as it limits the choice of antimicrobial agents for treatment of infections.
Abstract: Detection of plasmid-mediated (P-M) AmpC beta-lactamase-producing isolates is considered critical for epidemiologic studies and hospital infection control, but the documents of the Clinical and Laboratory Standards Institute do not contain any recommendation for the phenotypic detection. In this study, phenotypic detection methods, cefoxitin-Hodge test and induction test, were evaluated using cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae isolates. The cefoxitin-Hodge test detected all bla(CMY-10), and 97.4% of bla(CMY-2) allele-positive isolates, but only 57.3% of bla(DHA-1) allele-positive isolates. Induction test with an aztreonam and an amoxicillin-clavulanic acid disk was more sensitive than with cefoxitin disk, which detected 86.6% of bla(DHA-1) allele-positive isolates. These phenotypic tests should be useful to screen P-M AmpC beta-lactamase-producing E. coli and K. pneumoniae isolates.
Abstract: The 5th year KONSAR surveillance in 2001 was based on routine test data at 30 participating hospitals. It was of particular interest to find a trend in the resistances of enterococci to vancomycin, of Enterobacteriaceae to the 3rd generation cephalosporin and fluoroquinolone, and of Pseudomonas aeruginosa and acinetobacters to carbapenem. Resistance rates of Gram-positive cocci were: 70% of Staphylococcus aureus to oxacillin; 88% and 16% of Enterococcus faecium to ampicillin and vancomycin, respectively. Seventy-two percent of pneumococci were nonsusceptible to penicillin. The resistance rates of Enterobacteriaceae were: Escherichia coli, 28% to fluoroquinolone; Klebsiella pneumoniae, 27% to ceftazidime, and 20% to cefoxitin; and Enterobacter cloacae, > or =40% to cefotaxime and ceftazidime. The resistance rates of P. aeruginosa were 21% to ceftazidime, 17% to imipenem, and those of the acinetobacters were > or =61% to ceftazidime, aminoglycosides, fluoroquinolone and cotrimoxazole. Thirty-five percent of non-typhoidal salmonellae were ampicillin resistant, and 66% of Haemophilus influenzae were beta-lactamase producers. Notable changes over the 1997-2001 period were: increases in vancomycin-resistant E. faecium, and amikacin- and fluoroquinolone-resistant acinetobacters. With the increasing prevalence of resistant bacteria, nationwide surveillance has become more important for optimal patient management, for the control of nosocomial infection, and for the conservation of the newer antimicrobial agents.
Abstract: In vitro activities of DA-7867, a novel oxazolidinone, were compared to those of linezolid and commonly used antimicrobials. DA-7867 had the lowest MIC for 90% of the aerobic gram-positive bacterial strains tested, </=0.25 micro g/ml, and it was more potent than linezolid.
Abstract: OBJECTIVES: This study was performed to examine the cause of the increase in quinolone-resistant Neisseria gonorrhoeae (QRNG) observed in Korea. METHODS: The antimicrobial susceptibilities of 190 isolates of gonococci from Korea in 2000 were examined by NCCLS methods, and subsets of these isolates underwent mutation analysis of the quinolone resistance-determining regions (QRDRs) of gyrA and parC. Molecular epidemiological characterization of 25 Korean isolates and 54 isolates from overseas was performed by pulsed-field gel electrophoresis (PFGE) and the results compared. RESULTS: Most (172, 90.5%) of the 190 gonococci tested displayed reduced susceptibility to ciprofloxacin. All strains with high-level ciprofloxacin resistance (ciprofloxacin MIC >/= 4 mg/L) contained a double amino acid alteration at the 91 and 95 positions in the QRDR of GyrA and a single alteration in ParC. PFGE types of high-level QRNG in Korea were mostly different from those of other nearby countries. CONCLUSIONS: These results suggest that the observed increase in ciprofloxacin-resistant isolates is due to the mutation and spread of Korean multiclonal isolates rather than importation from overseas.
Abstract: Metallo-beta-lactamase (MBL)-producing Pseudomonas spp. and Acinetobacter spp. were prevalent in Korean hospitals. In this study, the prevalence and presence of MBL-producing isolates among imipenem-nonsusceptible and imipenem-susceptible isolates, respectively, were screened. The genetic and phenotypic characteristics of MBL-producing isolates were determined. Among imipenem-nonsusceptible isolates, 52 (11.1%) of 467 Pseudomonas spp. were blaVIM-like allele-positive, and 33 (15.1%) of 218 Acinetobacter spp. were either blaVIM- or blaIMP-like allele-positive. One blaVIM-like allele-positive isolate of Acinetobacter spp. was detected among 84 imipenem-susceptible Acinetobacter isolates. The minimum inhibitory concentration for 90% of isolates of imipenem was higher (>128 microg/mL) for Pseudomonas spp. than Acinetobacter spp. (16 microg/mL), although both had blaVIM-like allele. The source of MBL-producing isolates was mostly the sputum and urine of patients in the intensive care unit. Pulsed-field gel electrophoresis analysis suggested the intra- and inter-hospital spread of MBL-producing strains at some hospitals. In conclusion, blaVIM-like allele-positive P. aeruginosa remained highly prevalent, and the proportion of blaIMP-like allele-positive Acinetobacter spp. has increased significantly in most Korean hospitals.
Abstract: Continued antimicrobial resistance surveillance can provide valuable information for the empirical selection of antimicrobial agents for patient treatment, and for resistance control. In this 6th annual study for 2002, the susceptibility data at 39 Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) hospitals were analyzed. Resistance rates of S. aureus were 67% to oxacillin, and 58% to clindamycin. The ampicillin and vancomycin resistance rates of E. faecium were 89% and 16%, respectively. To penicillin, 71% of S. pneumoniae were nonsusceptible. Resistance rates of E. coli were 11% to cefotaxime, 8% to cefoxitin, and 34% to fluoroquinolone, and those of K. pneumoniae were 22% to ceftazidime, and 16% to cefoxitin. Lowest resistance rates to cephalosporins shown by E. cloacae and S. marcescens were to cefepime, 7% and 17%, respectively. This is the first KONSAR surveillance, which detected imipenem-resistant E. coli and K. pneumoniae. To imipenem, 22% of P. aeruginosa and 9% of Acinetobacter spp. were resistant. Trends of resistances showed a slight reduction in MRSA and in penicillin- nonsusceptible S. pneumoniae, but an increase in ampicillin-resistant E. faecium. Ampicillin-resistant E. coli and H. influenzae remained prevalent. Compared to the previous study, amikacin- and fluoroquinolone- resistant Acinetobacter spp. increased to 60% and 62%, respectively. Ceftazidime- resistant K. pneumoniae decreased slightly, and imipenem- resistant P. aeruginosa and Acinetobacter spp., and vancomycin-resistant E. faecium increased. In conclusion, vancomycin-resistant E. faecium, cefoxitin-resistant E. coli and K. pneumoniae, and imipenem-resistant P. aeruginosa and Acinetobacter spp. increased gradually, and imipenem- resistant E. coli and K. pneumoniae appeared for the first time. Continued surveillance is required to prevent further spread of these serious resistances.
Abstract: A chloramphenicol-resistant strain of Salmonella enterica serovar Typhi was first noted in Korea in 1992, when a resistant isolate was detected in a returned traveler. Continued isolation of multidrug-resistant (MDR) strains thereafter in other settings prompted a retrospective analysis of laboratory records and phenotypic and genotypic analyses of 12 chloramphenicol-resistant isolates. Among these, one isolate was resistant only to chloramphenicol, and the other isolates were also resistant to ampicillin and co-trimoxazole. MDR was transferred by conjugation from 9 of the 11 isolates. PCR showed that all isolates had an incompatible group HI1 plasmid, and oriT was detected in 10 isolates, which included strains with an unsuccessful transfer of resistance. All of the ampicillin-resistant isolates had a beta-lactamase band of pI 5.4 and bla(TEM) alleles. A PCR amplicon from an isolate showed that the sequences were identical to those of bla(TEM-1), suggesting that all isolates had a TEM-1 beta-lactamase. All isolates had class 1 integrons: 10 isolates had integrons of ca. 1.2 kb with dhfr7 gene cassettes, and 1 isolate had an integron of ca. 2.3 kb with aacA4 and bla(OXA-1)-like gene cassettes. The pulsed-field gel electrophoresis patterns of 7 of 11 MDR isolates were identical and indistinguishable from those reported for isolates in India and Indonesia. In conclusion, some of the MDR strains in Korea are related to those in other Asian countries. Susceptibility testing became necessary for selection of antimicrobial agents for the optimal treatment of patients with the emergence of MDR Salmonella serovar Typhi in Korea.
Abstract: PER-1, an extended-spectrum beta-lactamase, has been reported only in Europe. We detected PER-1 in 53 of 97 acinetobacters in Korea, mainly in the sputum of intensive care unit patients. Pulsed-field gel electrophoresis analysis suggested that clonal spread had occurred. Only PCR reliably detected PER-1 producers. PER-1 producers may also exist in other Asian countries.
Abstract: OBJECTIVES: Extended-spectrum beta-lactamase (ESBL)-producing non-typhoidal Salmonella (NTS) isolates in Korea were characterized. PATIENTS AND METHODS: Five isolates of ESBL-producing NTS were isolated from stool specimens of three infants and two adults with diarrhoea. Two infants acquired the infection in the community, and three other infections were hospital acquired. RESULTS: The isolates were one each of serovars Saintpaul, Stanley and Agona, and two Enteritidis. Cell sonicates of the isolates hydrolysed cefotaxime more efficiently than ceftazidime, and had beta-lactamase bands of approximate isoelectric points 6.0 and 7.4. Sequencing revealed that the beta-lactamases were TEM-52 and an OXA type. The blaOXA gene was located on a class 1 integron. Cefotaxime resistance, associated with TEM-52, was transferred by conjugation. Identical pulsed-field gel electrophoresis patterns of XbaI-digested genomic DNA were observed in initially beta-lactam-susceptible serovar Agona isolates and subsequent ESBL-producing isolates from an infant, and in two isolates of serovar Enteritidis from two different patients. CONCLUSIONS: This study suggests that TEM-52-producing NTS is spreading both clonally and horizontally in Korea.
Abstract: We determined the occurrence of acquired metallo-b-lactamase (MBL)-producing bacteria in Korean hospitals. Among the isolates nonsusceptible to imipenem that were collected from 28 hospitals from 2000 to 2001, 44 (11.4%) of 387 Pseudomonas spp. and 38 (14.2%) of 267 Acinetobacter spp. produced MBL and had alleles of blaVIM-2 or blaIMP-1. MBL-producing isolates were detected in 60.7% of the hospitals.
Abstract: We investigated the phenotypic and genetic properties of metallo-beta-lactamase-producing Pseudomonas isolates collected at a tertiary-care hospital in Korea since 1995. The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates reached 16% in 1997, when 9% of the resistant organisms were found to produce VIM-2 beta-lactamase, a class B enzyme previously found only in P. aeruginosa isolates from Europe. VIM-2-producing isolates of Pseudomonas putida were also detected. Resistance was transferable from both these species to P. aeruginosa PAO4089Rp by filter mating, although the resistance determinant could not be found on any detectable plasmid. Serotyping showed that many of the VIM-2-producing P. aeruginosa isolates belonged to serotypes O:11 and O:12, and pulsed-field gel electrophoresis of XbaI-digested genomic DNA revealed that many had identical profiles, whereas the P. putida isolates were diverse. Sequencing showed that the bla(VIM-2) genes resided as cassettes in class 1 integrons. In contrast to previous VIM-encoding integrons, the integron sequenced from a P. aeruginosa isolate had bla(VIM) located downstream of a variant of aacA4. bla(VIM) also lay in a class 1 integron in a representative P. putida strain, but the organization of this integron was different from that sequenced from the P. aeruginosa strain. In conclusion, the metallo-beta-lactamase produced by these imipenem-resistant Pseudomonas isolates was VIM-2, and the accumulation of producers reflected clonal dissemination as well as horizontal spread. Strict measures are required in order to control a further spread of resistance.
Abstract: PURPOSE: To describe two cases of bacterial keratitis with atypical mycobacteria after laser in situ keratomileusis (LASIK). METHODS: Two cases of non-tuberculous mycobacterial keratitis occurred in the interface between the stromal bed and flap, 20 days and 14 days after LASIK. The keratitis progressed slowly and worsened after attempts were made to remove the colonies. Mycobacterium fortuitum was confirmed 2 months after initial presentation following culture of the excised flap tissue in one case, and Mycobacterium chelonae was identified by culture of removed material and by RT-PCR with primers in the other case. The patients were treated medically and by surgical flap removal. RESULTS: In the first case, the keratitis was controlled only after removal of the partially melted flap and intensive medical treatment. In the second case, the lesion cleared after 2 months of antibiotics, but after tapering of antibiotics, the infiltrate progressed. Eventually, the keratitis was controlled after removal of the flap. CONCLUSIONS: Non-tuberculous Mycobacterium should be considered as one of the causes of keratitis when presenting as white colonies in the lamellar bed after LASIK. Treatment for 2 months may not be enough to eradicate the infection and excision of the flap may be necessary.
Abstract: Serratia marcescens is an important nosocomial pathogen which is often resistant to multiple antimicrobial agents. An imipenem-resistant S. marcescens isolate from a urine specimen was found to carry a bla(VIM-2) gene cassette on a class 1 integron. This finding indicates that bla(VIM-2) is presently spreading even to Serratia spp. in Korea, which could compromise the usefulness of carbapenem in the treatment of multi-resistant Gram-negative bacilli infections. Clinical laboratory should be able to detect the VIM-2-producing isolates with even low carbapenem MIC.
Abstract: Carbapenem-resistant Acinetobacter spp. used to be rare, but are increasingly isolated in Korea. Among 28 isolates of imipenem-resistant Acinetobacter spp. found in a Korean hospital in 1998 and 1999, 14 produced metallo-beta-lactamases. The bla(VIM-2) gene was detected, by PCR, in 11 and two isolates of Acinetobacter baumannii and Acinetobacter genomospecies 3, respectively, and bla(IMP-1) in one isolate of A. baumannii. The MICs of imipenem for the isolates were 8-32 mg/L. PFGE analysis of SmaI-digested genomic DNA gave identical patterns in eight of 11 bla(VIM-2)-positive A. baumannii isolates from respiratory specimens of ICU patients. The bla(VIM-2) gene cassettes in the isolates are identical to those from Pseudomonas aeruginosa isolates in Europe, but are inserted into new class I integrons In105 and In106. The attC site of the last cassette of the array in In106 is interrupted by the insertion of a putative class II intron. This is the first report of VIM-2 beta-lactamase-producing A. baumannii and Acinetobacter genomospecies 3. Production of the VIM-2 enzyme presents an emerging threat of carbapenem resistance among Acinetobacter spp. in Korea.
Abstract: Cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae are widespread in Korea. Significant proportions of them are considered to be CMY-1 producers. For effective screening of CMY-1 producers, the Hodge test was modified by using a cefoxitin disk and the performance was evaluated. The sensitivity and specifity of the test were 100% and 94.9%, respectively. The test was easier to perform than the three-dimensional extract test. This modified test should be suitable for screening CMY-1-producing strains of E. coli and K. pneumoniae.
Abstract: Rapid detection of metallo-beta-lactamase (MBL)-producing gram-negative bacilli is necessary to prevent their dissemination. The method using a disk with imipenem plus 750 micro g of EDTA differentiated all MBL-producing pseudomonads, and the sensitivity and specificity for acinetobacters were 95.7 and 91.0%, respectively. The imipenem-EDTA disks were stable for 12 and 16 weeks at 4 and -20 degrees C, respectively.
Abstract: OBJECTIVE: To verify the decrease of susceptibility to ciprofloxacin in Neisseria gonorrhoeae, determine the size of the recently reported new beta-lactamase plasmid and explain the high prevalence of penicillinase-producing Neisseria gonorrhoeae (PPNG). METHODS: Gonococci were isolated from prostitutes in Korea. Antimicrobial susceptibility was tested by NCCLS disk diffusion and agar dilution methods. Plasmid was isolated by an alkaline lysis method. Patterns of Nhel-digested genomic DNA were compared after pulsed-field gel electrophoresis (PFGE). RESULTS: The minimum inhibitory concentration of ciprofloxacin for 50% of the isolates rose from 0.015 mg/L in 1993 to 0.12 mg/L in 1996. The proportion of PPNG remained at 70% or over during the 5-year period. The size of a novel beta-lactamase plasmid, first reported in 1994, was determined to be approximately 3.2 MDa, and 48% of the PPNG isolates contained it. Twelve of 50 isolates had the same PFGE pattern and nine others another pattern. CONCLUSION: The rapid decrease of fluoroquinolone-susceptible gonococci suggests that in the near future the drug may become less useful for gonorrhea treatment. The new 3.2-MDa plasmid may have been introduced as a result of the recent increase in overseas travel. The PFGE pattern suggests that high prevalence of PPNG may be due to dissemination of a few resistant clones among the high-risk groups.
