Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) has been defined as S. aureus having the mecA gene or showing a minimum inhibitory concentration (MIC) of oxacillin higher than 4 mg/l. However, some clinical isolates are mecA-positive and oxacillin-susceptible. Therefore, we surveyed the occurrence of S. aureus having the mecA gene and an MIC of oxacillin of less than 2 mg/l (oxacillin-susceptible MRSA; OS-MRSA) in a total of 480 strains of S. aureus collected from 11 hospitals in different location in Japan isolated from 2003 through 2005. We found 6 strains matching the criteria for OS-MRSA. All 6 strains were staphylococcal cassette chromosome (SCC) mec-positive, without exception, and 4 strains showed the SCCmec type III-variant, which is unique in Japan. These OS-MRSAs were least resistant to oxacillin among the MRSAs tested and they were within the susceptible range to seven other beta-lactam antibiotics tested. Thus, OS-MRSA may become a high-resistant MRSA upon the treatment of patients with beta-lactam antibiotics. To characterize whether these OS-MRSAs were hospital-acquired or community-acquired MRSAs, we tested for the presence of the genes encoding toxins. Genes encoding hemolysin, exfoliative toxin, enterotoxin, toxic shock syndrome toxin-1, and Panton-Valentine leukocidin were found in 6, 4, 0, 0, and 0 strains, respectively. These results revealed that OS-MRSAs could be classified as a new type of MRSA that exhibits properties distinguishable from either hospital- or community-acquired MRSA. Coagulase typing of the OS-MRSAs supported the above conclusion. In this study, the occurrence of OS-MRSA at a certain frequency was noted; precautions are called for in the classification of oxacillin-resistant S. aureus and in the treatment of OS-MRSA infection.
Abstract: The Clinical and Laboratory Standards Institute (CLSI) amended the criteria for vancomycin susceptibility and resistance of Staphylococcus aureus in 2006. The earlier criteria had established that S. aureus with minimum inhibitory concentrations (MICs) of vancomycin of < or =4 microg/ml, 8 to 16 microg/ml, and > or =32 microg/ml were vancomycin-susceptible, -intermediate-resistant and -resistant, respectively. The revised recommendation states that bacteria showing vancomycin MICs of < or =2 microg/ml, 4 to 8 microg/ml, and > or =16 microg/ml are -susceptible, -intermediate-resistant, and -resistant, respectively. We examined, based on these new criteria, the vancomycin susceptibility of methicillin-resistant S. aureus (MRSA) strains isolated in Japan from 1978 through 2005 at 17 general hospitals. The results showed that, among 2446 MRSA isolates tested, 8 were classified as intermediate-vancomycin-resistant (VISA). Re-examination of vancomycin susceptibility in these 8 strains in 2006 revealed that 6 strains showed a vancomycin MIC of 4 microg/ml, as tested by the agar dilution method, broth dilution methods, and E-test; the 2 other strains had lost the vancomycin resistance. Pulsed-field gel electrophoresis (PFGE) of the chromosomal DNA of these strains exhibited five unique profiles; 2 strains isolated from the same hospital were identical. These results revealed that at least five different types of VISA strains could be identified in Japan so far according to the new CLSI criteria. All these VISA strains had type II staphylococcal cassette chromosome, mec. This study revealed, for the first time in Japan, the presence of intermediate vancomycin-resistant MRSA in this country.
Abstract: It is generally accepted that methicillin-resistant Staphylococcus aureus (MRSA) is also resistant to aminoglycoside antibiotics. We investigated trends of gentamicin and arbekacin susceptibilities and the prevalence of the genes encoding aminoglycoside-modifying enzymes (AMEs) for a total of 218 strains of MRSA isolated from blood specimens obtained from 1978 through 2002 in one hospital. The minimum inhibitory concentrations of gentamicin at which 50% of the strains were inhibited (MIC(50)) were > or =128 and 32 microg/ml for isolates obtained from 1978 to 1984 and from 1985 to 1989, respectively, and 0.5 microg/ml for isolates obtained from 1990 to 2002. The MIC(90) of gentamicin was consistently > or =128 microg/ml. Investigation of the occurrence of AME revealed that the MIC(50) of gentamicin was highly correlated with the presence of aac(6')/aph(2'') encoding aminoglycoside acetyl/phosphotransferase. The MIC(50) of arbekacin was 2 microg/ml for strains isolated in 1978-1984 and </=0.5 microg/ml for strains isolated from 1985 to 2002. The MIC(90) of arbekacin was 8 microg/ml for the strains isolated in 1978-1989 and 1 to 2 microg/ml for strains isolated in 1990-2002. Though it has been established that AAC(6')/APH(2'') modifies arbekacin, the trend of arbekacin resistance was not necessarily consistent with the presence of this enzyme. However, the prevalence of both aac(6')/aph(2'') and aph(3')-III in the strains isolated from 1978 through 2002 was correlated with the MIC(90) values of arbekacin. Thus, it is most likely that APH(3')-III, in addition to AAC(6')/APH(2''), is somehow involved in arbekacin resistance in S. aureus. Our results imply that gentamicin- and arbekacin-resistant MRSAs have consistently decreased for the past 25 years and that this finding is, most likely, attributable to the declining prevalence of genes encoding for AMEs.
Abstract: We investigated trends of beta-lactam antibiotic susceptibility in a total of 218 strains of blood-borne methicillin-resistant Staphylococcus aureus (MRSA) isolated from 1978 through 2002 at a middle-size geriatric hospital in Tokyo; the strains were classified by the MRSA marker, staphylococcal cassette chromosome mec (SCCmec). The minimum growth inhibitory concentration (MIC) of cloxacillin at which 50% of the strains were inhibited (MIC50) was 2 microg/ml in the strains isolated in 1978-1984 and 32 to 64 microg/ml in the strains isolated subsequently. Similarly, the MIC50 values of cefazolin and imipenem in the 1978-1984 isolates were 16 and <or=0.25 microg/ml, respectively, and those in the strains isolated subsequently were 128 and 16 to 32 microg/ml, respectively. These results indicated that the MRSA strains isolated after 1985 had gained high-level resistance to beta-lactam antibiotics. The type of SCCmec was investigated by polymerase chain reaction (PCR). We observed an elevated frequency of type II SCCmec, from about 15% in the strains isolated in 1978-1984 to about 50% in the 1985-1989 isolates, and the frequency reached and remained at about 90% subsequently. These results imply that the high-level beta-lactam antibiotic resistance of the MRSA strains isolated after 1985 is most likely due to the increased integration of type II SCCmec.
Abstract: An erythromycin analogue, 11,12-di-O-iso-butyryl-8,9-anhydroerythromycin A 6,9-hemiketal (1b), was found to be a potential anti-MRSA and anti-VRE agent. The use of copper catalyzed azide-acetylene cycloaddition, and click chemistry, readily provided 10 types of triazole analogues of 1b in good to nearly quantitative yield. Among the library, 5b exhibited activity against MRSA and VRE bacterial strains, representing more than twice the potency of 1b.
Abstract: We report here an outbreak of beta-lactam-induced vancomycin-resistant methicillin-resistant Staphylococcus aureus (MRSA; BIVR) at one of the Cancer-Institute-affiliated hospitals in Tokyo. We examined a total of 500 strains (100 per year) of clinically isolated MRSA from 1998 to 2002. The detection rates of BIVR in the years 1998, 1999, 2000, 2001, and 2002 were 10%, 9%, 49%, 15%, and 19%, respectively. To investigate the cause of the high incidence of BIVR detection in the year 2000, we carried out pulsed-field gel electrophoresis (PFGE) of the SmaI-digested chromosomal DNA of BIVR and MRSA. The results showed that 96% of the BIVR strains isolated in 2000 were classified as an identical DNA type "A", while only 47% of the MRSA strains were classified as this type. We concluded, based on these results, that this hospital had a nosocomial infection of BIVR in the year 2000. An important message given by this study would be that nosocomial BIVR infection could occur in any hospital where MRSA infection is treated with vancomycin and beta-lactam antibiotics.
Abstract: Since a method of rapidly detecting extended-spectrum beta-lactamase (ESBL) production in gram-negative isolates from patients with severe infection is urgently required, the present study of a novel commercial kit was conducted. The Cica-Beta Test I (Kanto Chemical, Tokyo, Japan) is designed for the rapid detection of ESBL in gram-negative bacteria directly from isolated colonies in a 15-min protocol. In this study, a total of 304 strains of Klebsiella spp., Escherichia coli and Proteus mirabilis were tested using the novel kit and the phenotypic confirmatory disk test using cefotaxime and ceftazidime with and without clavulanate. The kit showed 95.5 and 98.1% sensitivity and specificity, respectively, as compared to the disk test, and thus proved to be an appropriate tool for the rapid detection of ESBL.
Abstract: The concomitant use of low concentration beta-lactam antibiotics antagonizes the activity of vancomycin against some strains of MRSA. These strains, called beta-lactam antibiotic-induced vancomycin resistant MRSA (BIVR), have been increasing for a number of years. We previously reported that the combination of VCM and ceftizoxime displayed this antagonism not only in vitro, but also in vivo, in a systemic infection caused by BIVR in mice. In the present study, we validated the antagonism in combinations of VCM with other beta-lactams, i.e., flomoxef (FMOX), ampicillin (AMPC), azthreonam (AZT) and imipenem/cilastatin (IPM/CS), in systemic infections and pneumoniain in mice. The survival rate of the mice with systemic infections caused by BIVR treated with combinations of FMOX, AMPC, AZT, and IPM/CS with VCM were significantly lower than with VCM monotherapy, and the number of residual viable cells in the kidneys of mice treated with combinations of FMOX and IPM/CS with VCM were significantly higher than with VCM monotherapy The number of residual viable cells in the lungs of mice with pneumonia caused by BIVR treated with the combination of IPM/CS and VCM was significantly higher than with VCM monotherapy. On the other hand, the survival rate with combination therapy consistings IPM/CS plus teicoplanin (T EIC) was significantly higher, and the number of residual viable cells in the kidney was significantly lower, than with TEIC monotherapy alone. In the mice with pneumonia, the number of residual viable cells in the lung after combination therapy with IPM/CS and TEIC was significantly lower than with TEIC monotherapy. Combination therapy with beta-lactams plus VCM showed antagonistic in models of systemic infection and pulmonary infection caused by BIVR, whereas combination therapy consisting of a beta-lactam plus TEIC had a synergistic effect in the same models, even though VCM and TEIC are member of the same glycopeptide antibiotic class.
Abstract: We synthesized 7-substituted-3-(2,4-dinitrostyryl)cephalosporin derivatives which were Nitrocefin analogs, for detecting extended spectrum beta-lactamase (ESBL) specifically. HMRZ-86 which has carboxypropyloxyimino group on 7-aminothiazolacetamide substituent were not hydrolyzed by class A, C and D beta-lactamases, but it was hydrolyzed by ESBL and metallo beta-lactamase (class B), then its color changed from yellow to red. The hydrolysis of metallo beta-lactamase was inhibited by adding sodium mercapto acetic acid (SMA). Therefore HMRZ-86 is a useful chromogenic agent to detect ESBL specifically.
Abstract: We could not detect hetero-vancomycin-intermediate resistant Staphylococcus aureus (hetero-VISA), according to the definition of hetero-VISA, from the clinical isolates of 140 methicillin-resistant S. aureus (MRSA) strains. However, 15 beta-lactam antibiotic-induced vancomycin-resistant MRSA (BIVR) strains were detected from the same strains. We screened 1882 MRSA clinical isolates obtained in 2002 from 21 institutes throughout Japan. The detection rate of blood-isolated BIVR was 12.6% (19/151), and that of nonblood-isolated BIVR was 4.9% (85/1731; P < 0.001; chi2 test). Uridine-diphosphate-N-acetylmuramyl-L: -alanyl-D: -isoglutamyl-L: -lysine, used as the peptidoglycan material of S. aureus, showed the same results as beta-lactam antibiotics in BIVR.
Abstract: The in vitro combination effects of pazufloxacin (PZFX) with an anti-MRSA drug such as vancomycin (VCM), teicoplanin (TEIC), arbekacin (ABK), minocycline (MINO), rifampicin (RFP) and sulfamethoxazole-trimethoprim (ST) were investigated against 26 strains of beta-lactam antibiotic induced vancomycin-resistant MRSA (BIVR) by the checkerboard method. The additive and synergistic effects were observed with the combination of PZFX and VCM (50%, 13/26 strains), PZFX and TEIC (96%, 25/26 strains), PZFX and ABK (65%, 17/26 strains), PZFX and MINO (46%, 12/26 strains), PZFX and ST (54%, 14/26 strains). The synergistic effects were observed with the combination of PZFX and TEIC (4%, 1/26 strains), PZFX and ABK or MINO (15%, 4/26 strains). The antagonistic effects were observed with only PZFX and MINO (12%, 3/26 strains), others were all indifference.
Abstract: We developed a simple method that can replace the polymerase chain reaction (PCR) to distinguish between vancomycin-resistant enterococci (VRE) with the vanA, vanB and vanC genes. The method is based on induction of teicoplanin resistance by vancomycin in vanB-VRE, while the two compounds have a synergistic effect in vanC-VRE. In addition, vanA-VRE shows resistance to both vancomycin and teicoplanin, and both the compounds can induce resistance to vanA-VRE. Utilising these properties, we attempted to develop a simple method to distinguish between vanA, vanB and vanC. We compared our simple method with the PCR method in 43 strains of vanA-VRE, 35 strains of vanB-VRE and 37 strains of vanC-VRE. The results were 100% consistent with that obtained by PCR.
Abstract: Despite the fact that the combination of vancomycin and a beta-lactam antibiotic are known to act synergistically on vancomycin-susceptible Staphylococcus aureus (VSSA), some MRSA have emerged showing antagonism to the combination of vancomycin and a beta-lactam antibiotic. These MRSA are called beta-lactam antibiotic-induced vancomycin resistant MRSA (BIVR). A method based on this antagonistic phenomenon has been devised to detect BIVR strains. The method inhibits the VSSA strain but allows the BIVR strain to grow. Forty-six commercially available beta-lactam antibiotics induced the vancomycin-resistance. Using this detection method, 717 MRSA clinical isolates obtained from eight institutes throughout Japan were thus screened and 6.3% of these were detected as BIVR when judged at 48 h.
Abstract: Recently, beta-lactam antibiotic induced vancomycin-resistant MRSA (BIVR) has been reported increasingly in Japan. Between 1998 and 2002, we tried to detect BIVR from 500 strains of MRSA in a cancer hospital. And the difference of the detection rate under condition of pre-culture with or without ceftizoxime was compared. The detection rate of BIVR under condition of pre-culture with 1.0 mg/L of ceftizoxime was 20.4% (102/500), and without ceftizoxime was 9% (45/500). That of preculture with 1.0 mg/L of ceftizoxime was higher than those without ceftizoxime with the significant difference. (p < 0.001; McNemar-t examination). In comparing each department, the detection rate of BIVR from Chemotherapy, Head & Neck, and Urology department was 33.3%, 27.0%, and 20.0%, respectively. These results mean that addition of beta-lactam as ceftizoxime in pre-culture induces the ability of resistance to vancomycin for MRSA having a capacity as BIVR.
Abstract: A patient with infective endocarditis (IE) caused by methicillin-resistant Staphylococcus aureus (MRSA) was treated with vancomycin (VAN). VAN was ineffective, although therapeutic drug monitoring (TDM) indicated that the recommended trough level was maintained. Five MRSA isolates obtained at various times were analyzed to determine the minimum inhibitory concentration (MIC) and were subjected to population analysis, simulation analysis pulsed-field gel electrophoresis (PFGE). MRSA susceptible to VAN was isolated before and during the early stage of treatment, while an MRSA strain showing reduced VAN MIC was isolated during treatment. Simulation analysis indicated that the viable bacterial count only decreased to 10(-3) to 10(-4) cells after 72 h of incubation. The five MRSA strains isolated at various times were identical by PFGE.
Abstract: Mu3 strain with heterogeneous intermediated-resistance to vancomycin (hetero-VISA) reported in 1997, also have possessed a character of an antagonistic effect of beta-lactam antibiotics and vancomycin. Mu3 is only strain which satisfies the definition of hetero-VISA in Japan. But, MRSA with antagonistic effects of beta-lactam antibiotics and vancomycin, was reported by many institutions. To separate hetero-VISA, we called "beta-lactam antibiotic induced vancomycin-resistant MRSA (BIVR)". But the detection rate of clinical isolated BIVR in Japan is unknown, we reported on the detection method and the epidemiological investigation for BIVR. Mu 3 agar containing 4 micrograms/mL of vancomycin is used to detect BIVR. Mu3 strains were spread on the agar, BIVR can grow around the paper disc impregnated with ceftizoxime or grow on the whole surface on Mu 3 agar after incubation. The detection rate of BIVR was 45 in 717 (6.3%) clinical isolated strains. In detected strains as BIVR, the number of strains with grown on the whole surface of Mu3 agar showing a high resistance to vancomycin were 10 strains (1.4%). Besides, from 106 strains of blood isolates MRSA, BIVR were detected 16 strains (15.1%), from 611 strains of non-blood isolates MRSA, BIVR were detected 29 strains (4.7%) (P < 0.0001). In BIVR strains grown on the whole surface of Mu3 agar, the number of BIVR strains isolated from blood were 8 in 106 (7.5%), from non-blood were 2 in 611 (0.3%) (P < 0.0001). On one side, hetero-VISA were not detected from all of BIVR growing on the whole surface of Mu3 agar. As a result, detection method and the definition of BIVR were quite different from those of hetero-VISA. An existence of BIVR in Japan was confirmed, we thought that the high detection rate of BIVR isolated from blood compared with that of non-blood showed the pathogenecity of BIVR which contribute to MRSA infections.
Abstract: The combination of vancomycin and beta-lactam antibiotic synergistically is known to act on vancomycin-susceptible Staphylococcus aureus (VSSA). But some MRSA with the antagonism in the combination of vancomycin and beta-lactam antibiotic was identified in Japan. We called the MRSA "beta-lactam antibiotic-induced vancomycin-resistant MRSA (BIVR)", to distinguish it from hetero-VISA. The percentage of hetero-VISA isolated in Japan that Hiramatsu et al. reported in The Lancet in 1997 was that of "candidate-hetero-VISA" because it did not satisfy the criteria for detection of hetero-VISA that they proposed. Therefore, except for Mu3, a strictly defined hetero-VISA strain has never been detected in Japan. However, BIVR is certainly detectable in Japan. We performed a retrospective study of BIVR in 189 MRSA strains isolated from blood between 1978 and 1999 at the same institution. To performed a retrospective study, 189 MRSA strains were divided such as 1978-1984 (45strains), 1985-1989 (45strains), 1990-1994 (49strains), 1995-1999 (50strains). MIC90 of anti-MRSA drugs according to above chronological transition were 2, 2, 2, 1 as vancomycin, 2, 1, 1, 1 as teicoplanin, and 8, 8, 1, 1 microgram/mL as arbekacin, respectively, and then the detection rate of BIVR was 2.2, 2.2, 6.1, 10.4%, respectively. The BIVR detection rate in MRSA isolated from blood at 14 institutions was 14.8% (12/81) in 1999-2002, and that of non-blood was 4.6% (42/905) (p < 0.001; chi 2-t examination). Of particular importance is that the percentage of BIVR isolated from blood is higher than that from non-blood, and the detection rate of BIVR from blood increases annually.
Abstract: OBJECTIVES: Staphylococcus aureus with low-level resistance to vancomycin (VLSA) which could develop into vancomycin-resistant S. aureus (VRSA) is most important. However, VLSA is difficult to detect by standard laboratory methods. We describe here improved methods to detect VLSA. METHODS: Three methicillin-resistant S. aureus (MRSA) strains, designated Fu6, Fu10, and Fu18, were sequentially isolated from the burn wound site of a patient, during vancomycin therapy. The properties of these strains were compared with those of reference strains Mu3 and Mu50 (previous resistant isolates from other patients). RESULTS: The isolated strains, Fu10 and Fu18, had identical phenotypes and genotypes. The vancomycin resistance of Fu10 was equivalent to that of strain Mu3, whereas Fu18 had much higher vancomycin resistance than Fu10 and Mu3, although reaching the level of Mu50. Fu18 showed similar growth to Mu50 on gradient gels and on Mu3 medium. CONCLUSIONS: Our data indicate that the VLSA developed vancomycin resistance during exposure to vancomycin in vivo. The population analysis of tested VLSA and vancomycin intermediately resistant S. aureus (VISA) indicates that a penem at relatively low concentrations induced a significant increase in the number of vancomycin-resistant subpopulations. Furthermore, we confirmed that gradient gel analysis and Mu3 medium are simple and useful methods for the detection of VLSA judged as VSSA by its conventional MIC alone.
Abstract: We tested the combined activity of vancomycin and seven beta-lactam antibiotics against Staphylococcus aureus clinical strain Mu3, which displays heterogeneous resistance to vancomycin. When combined with vancomycin, four of the seven tested beta-lactams exhibited an additive effect at or near their MICs, while all showed an antagonistic effect at lower, sub-MIC levels. This study implicated the unpredictable nature of combination therapy of beta-lactams and vancomycin against S. aureus with reduced susceptibility to vancomycin.
Abstract: The effect of arbekacin (ABK), vancokmycin (VCM) and teicoplanin (TEIC) on the production of toxic shock syndrome toxin-1 (TSST-1) by methicillin-resistant Staphylococcus aureus was examined. In logarithmic-phase cultures, ABK, VCM and TEIC inhibited TSST-1 production by 85, 10 and 25%, respectively, at the concentration of one-fourth the each MIC. In stationary-phase cultures, ABK inhibited TSST-1 production by 50% or 90% compared with the control at the concentration of 4.0 micrograms/ml or 5.0 micrograms/ml respectively. VCM and TEIC did not inhibit TSST-1 production at the concentration of 8.0 micrograms/ml or lower. In human blood cultures, TSST-1 production was inhibited by ABK by 50% at 0.04 microgram/ml (1/256 of Cmax), but not inhibited by VCM and TEIC at the concentration of 1/16 of Cmax or lower. It has been already known that ABK has higher bactericidal activity than VCM and TEIC. ABK combined the inhibition of TSST-1 production with high bactericidal activity in both bacterial growth phases, and therefore ABK should be considered for the treatment of TSST-1-mediated MRSA-infection.
Abstract: We evaluated a series of novel cephem antibiotics, N-alkylpyridinium (alkyl group), N-carboxyethylpyridinium (carboxylic group), N-sulfoethylpyridinium (sulfonic group) and N-alkylquaternary ammonium salts (ammonioethyl group), N-alkyl-aromatic-quaternary ammonium salts and N-alkyl-heterocyclic quaternary ammonium salts (cyclic group) as vinylthio pyridinium derivatives at the C-3 position and hydroxyiminoaminothiazol at the C-7 position, for their activity against methicillin-resistant Staphylococcus aureus (MRSA) and their solubility, by measuring the minimum inhibitory concentrations (MICs) and the dissolving test in phosphate buffer. All tested compounds, except for the alkyl group, showed good solubility (>10%) in 1/15 M phosphate buffer (pH 7.2). The concentrations required to inhibit 80% of the bacterial strains (MIC80s) of the alkyl group, carboxylic group, sulfonic group, ammonioethyl group and cyclic group against MRSA were 1.56, 12.5-25, 6.25, 1.56 and 1.56 microg/ml, respectively. These results indicated that the ammonioethyl and cyclic groups yield the maximum anti-MRSA and anti-Enterococcus faecalis activity, and also good water solubility.
Abstract: Staphylococcus aureus Mu50, which has reduced susceptibility to vancomycin, has a remarkably thickened cell wall with an increased proportion of glutamine nonamidated muropeptides. In addition, Mu50 had enhanced glutamine synthetase and L-glutamine D-fructose-6-phosphate aminotransferase activities, which are involved in the cell-wall peptidoglycan synthesis pathway. Furthermore, significantly increased levels of incorporation of (14)C-labeled D-glucose into the cell wall was observed in Mu50. Unlike a femC mutant S. aureus strain, increased levels of production of nonamidated muropeptides in Mu50 was not caused by lower levels of glutamine synthetase activity but was considered to be due to the glutamine depletion caused by increased glucose utilization by the cell to biosynthesize increased amounts of peptidoglycan. After the cells were allowed to synthesize cell wall in the absence or presence of glucose and glutamine, cells with different cell-wall thicknesses and with cell walls with different levels of cross-linking were prepared, and susceptibility testing of these cells demonstrated a strong correlation between the cell-wall thickness and the degree of vancomycin resistance. Affinity trapping of vancomycin molecules by the cell wall and clogging of the outer layers of peptidoglycan by bound vancomycin molecules were considered to be the mechanism of vancomycin resistance of Mu50. The reduced cross-linking and the increased affinity of binding to vancomycin of the Mu50 cell wall presumably caused by the increased proportion of nonamidated muropeptides may also contribute to the resistance to some extent.
Abstract: We report on a rare fatal case of postoperative toxic shock syndrome caused by infection with a highly virulent methicillin-resistant Staphylococcus aureus strain, designated Sak-1, which was found to be characteristic in its increased production of toxic shock syndrome toxin 1 in human whole blood (about 30-fold more than produced in Tod Hewitt broth). The strain also produced a high level of toxic shock syndrome toxin 1 in the circulating blood of mice experimentally infected with the strain.
Abstract: The susceptibility of Streptococcus agalactiae (S. agalactiae) clinical isolates of Juntendo University Urayasu Hospital, and type strain ATCC 13813 to beta-lactam antimicrobial agents was evaluated by means of macro-broth dilution MIC determination, killing kinetics and population analysis. When 10(6) cells of S. agalactiae were inoculated and cultured in Todd-Hewitt broth containing two-fold serial dilutions of penicillin, the viable cell count showed that about 10(2) cells survived irrespective of the penicillin concentration which ranged from 0.063 to 128 micrograms/ml. The result indicated that S. agalactiae had tolerance to penicillin (MICs were around 0.063 microgram/ml). Furthermore, the S. agalactiae strains were found to have a paradoxical response to penicillin in an acidic condition (pH 5.5). When the cell counts were performed at pH 5.5, about 10(2) cells survived at penicillin concentrations from 0.016 to 0.125 microgram/ml, while about 10(4) cells survived at the concentrations of 1 to 8 micrograms/ml. The antibiotic tolerance and paradoxical effects of S. agalactiae were also observed in killing kinetics. The ATCC 13,813 and 10 out of 11 clinical strains showed slow response to penicillin-mediated killing at pH 7.8 and ATCC 13,813 and one of the clinical strains showed a reduced response with increase in penicillin concentration at pH 5.5. These results suggested that the tolerance and paradoxical effect of S. agalactiae cells to beta-lactam antibiotics may be one of the reasons for frequent re-colonization of S. agalactiae at the time of delivery after the chemophylaxis in the 2nd trimester.
Abstract: Eleven clinical strains of MRSA which were detected as heterogeneously-resistant to vancomycin (hetero-VRSA) on Mu3-medium (a newly devised hetero-VRSA detecting medium) were subjected to a study to explore the therapeutic possibility of combination therapy. Combination effects of teicoplanin with six different beta-lactam antibiotics (imipenem, panipenem, meropenem, flomoxef, sulbactam/ampicillin, cefoselis), arbekacin, and minocycline were evaluated on the strains of Mu3, Mu50 and the above 11 strains. Combination of teicoplanin with five beta-lactam antibiotics individually (except for cefoselis) showed a synergistic effect, while that with cefoselis showed synergistic or additive effect. Neither indifference nor antagonism effect was observed in combination of seicoplanin with beta-lactam antibiotics on these MRSA strains. The degree of synergistic effect in combination with teicoplanin was the strongest in imipenem, followed by panipenem > meropenem > flomoxef > sulbactam/ampicillin > cefoselis in this order. The average FIC index of the beta-lactam antibiotics against these strains was 0.113, 0.124, 0.163, 0.230, 0.264 and 0.388, respectively. Arbekacin and minocycline showed variable of effects in combination with teicoplanine. In the case of arbekacin, the ratio of synergy, addition, indifference, and antagonism were 30.8, 30.8, 0 and 38.4%, respectively, and in the case of minocycline, they were 15.4. 7.7, 0 and 76.9%, respectively. Vancomycin activity against hetero-VRSA and VRSA is antagonized with beta-lactam antibiotics, while teicoplanin activity is synergistic or additive. It is known that MRSA is relatively easy to emerge resistance to teicoplanin. Therefore, teicoplanin is not desirable for a monotherapy. However, in a combination with beta-lactam antibiotics, teicoplanin appeared to be a promising agent for the treatment of MRSA infection.
Abstract: We evaluated the antibacterial activity of faropenem against penicillin-susceptible Streptococcus pneumoniae (PSSP) and penicillin-resistant S. pneumoniae (PRSP). It was shown that the minimum inhibitory concentrations against 90% of the clinically isolated strains (MIC90) of faropenem, penicillin G, cefaclor, cefcapene, and cefditoren against PSSP were 0.032, 0.063, 2, 0.25, and 0.125 micrograms/ml, respectively. While those against PRSP were 0.5, 2, > 128, 1, and 1 micrograms/ml, respectively. Furthermore, we evaluated the bactericidal activity, at the level of 1/4, 1, and 4 MIC, of faropenem and the above four reference antibacterial agents against PSSP and PRSP. Against PSSP No. 127, a sensitive strain to both penicillin G and cefcapene, faropenem showed almost the same bactericidal activity as those of reference agents. Against PSSP No. 108, a penicillin-susceptible and cephem-resistant strain, and PRSP No. 57, a resistant strain to both of penicillin and cephem, faropenem of 1 MIC showed bactericidal activity, but reference agents needed 4 MIC to show bactericidal activity.
Abstract: More than 90% of methicillin-resistant Staphylococcus aureus (MRSA) isolates produce a penicillin-binding protein PBP2' (or PBP2a) with low affinity for beta-lactam antibiotics. PBP2' is encoded by the mecA gene, a foreign gene integrated into the chromosome of methicillin-susceptible S. aureus (MSSA). DNA vaccination by injection of transgene-expressing plasmids has been demonstrated to elicit an immune response against transgene-encoded protein. We hypothesized that the application of DNA vaccination with the mecA sequence would elicit protective immunity against MRSA. This immunity was evoked by injection of a mecA-expressing plasmid into BALB/c mice. Anti-PBP2' antibody was detected in the sera obtained from the DNA-vaccinated mice. These sera produced a five-fold increase in phagocytosis of MRSA compared with sera from mice treated with control plasmid. However, there was no difference in phagocytosis of MSSA among these groups. In addition, the in-vivo antibacterial effect of DNA vaccination was demonstrated in mice infected with MRSA. Eight days after iv inoculation of 10(8) cfu of MRSA into mice, the number of bacteria in the kidneys obtained from mice vaccinated with mecA-expressing plasmid (1.48 +/- 0.27 x 10(5) cfu/mg kidney; n = 18) was significantly lower than that from mice vaccinated with negative control plasmid (3.59 +/- 0.57 x 10(5) cfu/mg kidney; n = 17) (P < 0.02) or that from sham-treated mice (3. 43 +/- 0.66 x 10(5) cfu/mg kidney; n = 9) (P < 0.02). Interestingly, PBP2' was found in both the bacterial membrane fraction and the supernatant, thus being accessible to serum antibodies. Together these observations indicate that PBP2' or the mecA sequence may be eligible as a candidate molecule for vaccination against MRSA.
Abstract: We have previously reported methicillin-resistant Staphylococcus aureus clinical strains, Mu50 and Mu3, representing two categories of vancomycin resistance: Mu50 representing vancomycin-resistant S. aureus (VRSA) with MICs > or = 8 mg/L, and Mu3 representing hetero-VRSA with MICs < or = 4 mg/L using standard MIC determination methods. The mechanisms of vancomycin resistance in these strains were investigated. These strains did not carry the enterococcal vancomycin-resistance genes, vanA, vanB, or vanC1-3, as tested by PCR using specific primers. However, both strains produced three to five times the amount of penicillin-binding proteins (PBPs) 2 and 2' when compared with vancomycin-susceptible S. aureus control strains with or without methicillin resistance; the amounts of PBP2 produced in Mu3 and Mu50 were comparable to those in the vancomycin-resistant S. aureus mutant strains selected in vitro. Incorporation of 14C-labelled Nacetyl-glucosamine into the cell was three to 20 times increased in Mu50 and Mu3, and release of the radioactive cell wall material was increased in Mu3 (and also in Mu50, though to a lesser extent), compared with control strains. The amounts of intracellular murein monomer precursor in these strains were three to eight times greater than those found in control strains. Transmission electron microscopy showed a doubling in the cell wall thickness in Mu50 compared with the control strains. Mu3 did not show obvious cell wall thickening. These data indicate that activated synthesis and an increased rate of cell wall turnover are common features of Mu3 and Mu50 and may be the prerequisite for the expression of vancomycin resistance in S. aureus.
Abstract: The mechanism of resistance was studied with vancomycin-resistant Staphylococcus aureus (VRSA) strain Mu50. It was demonstrated that the incorporation of 14C-N-acetylglucosamine into the cell wall of Mu50 was not suppressed in the presence of 8 microliters/ml of vacomycin, whereas it was completely suppressed in vancomycin-susceptible strains FDA209P and H-1. Increased binding of vancomycin to the wall of Mu50 was observed compared to the control strains: 1.7 x 10(16) (Mu50), 6.1 x 10(15) (209P), and 6.7 x 10(15) (H-1) vancomycin molecules/mg cell wall, respectively. Remarkable proportion of the cell-wall component muropeptides were non-amidated in the cell wall of Mu50. In concordance with this phenomena, peptidoglycan cross-linkage decreased strikingly in the Mu50 strain. Free D-Ala-D-Ala residues at the end of muropeptides in the pre-existing cell wall generated by decreased cross-linkage seems to account for increased vancomycin binding. The increase of vancomycin-resistance level is presumably caused by sequestration of vancomycin molecules from primary target point on cell membrane. It was considered that at least two phenotypic changes are required for the vancomycin resistance in the Mu50 strain. First, as we have described previously, is the activated cell wall synthesis, and second, the reduction of cross-linkage of peptidoglycan by production of non-amidated muropeptide precursors.
Abstract: The mechanism of vancomycin resistance in methicillin-resistant Staphylococcus aureus (MRSA) Mu50 was investigated. More than 3 times increase of the incorporation of 14C-GluNAc into the cell wall of Mu50 was observed compared to those of vancomycin-susceptible strains FDA209P, H-1, LR5P1. The amount of cytoplasmic murein-monomer precursor increased more than 3 times in Mu50 compared to those of control strains. There was an increased production of PBP1, PBP2, and PBP2', which were 1.51, 17.2, and 7.06 times greater, respectively, in Mu50 than those in H-1, and 2.38, 4.46, and 1.96 times greater respectively, than those in LR5P1. By transmission electromicrograph, it was shown that the cell wall of Mu50 was twice thicker than that of LR5P1. Increase of tightly-bound vancomycin to the cell wall fraction was observed in Mu50 when compared to those in FDA209P and H-1 strains. From these results, the increase of the vancomycin targets, free D-Ala-D-Ala residues in the cell wall, in number, due to the activated cell wall synthesis, and/or decrease of the cross-linkage of the cell wall was suggested to be the mechanism of vancomycin resistance in the Mu50 strain.
Abstract: The peptidoglycan compositions of vancomycin-resistant Staphylococcus aureus (VRSA) strain Mu50 (MIC 8 mg/L) and hetero-VRSA strain Mu3 (MIC 3 mg/L) were compared in order to understand the mechanism of vancomycin resistance. As compared with Mu3, the cell wall of Mu50 had increased amounts of glutamine-non-amidated muropeptides and decreased cross-linking of peptidoglycan with a greatly decreased dimer/monomer ratio of muropeptides. In agreement with this observation, the peptidoglycan of Mu50 bound 1.4 times more vancomycin than that of Mu3. The increase in non-amidated muropeptides and the reduced cross-linking of the cell-wall peptidoglycan may contribute to the vancomycin resistance by increasing the consumption of vancomycin by the pre-existing cell wall of Mu50 and reducing the amount of vancomycin reaching the cytoplasmic membrane where the vital targets of the antibiotic are situated.
Abstract: We have developed a new method of detecting clinical S. aureus strains possessing heterogeneous resistance to vancomycin (hetero-VRSA). The method exploits characteristic antagonism between vancomycin and beta-lactam antibiotics against the strain Mu3, a representative hetero-VRSA. The method comprises of the following procedures: 1) overnight culture of bacteria is streaked on brain heart infusion agar containing 4 micrograms/ml of vancomycin, 2) paper discs impregnated with any one of beta-lactam antibiotics are placed onto the plate, and 3) the plate is incubated at 37 degrees C and the cell growth was observed after 24 h and 48 h of incubation. The Mu3 cells were grown only around the beta-lactam discs due to the antagonism between vancomycin and beta-lactam against Mu3 cells. A total of 321 MRSA clinical strains isolated in 1995 and 1996 from 12 medical facilities in Japan were tested with this method. A total of 39 strains (12.1%; 24 h) and 67 strains (20.96%; 48 h) grew around the beta-lactam discs. All the 10 strains (representing 10 facilities), tested with the analysis of resistant subpopulations to vancomycin, showed similar heterogeneous patterns as observed with Mu3. The method was considered as a convenient and rapid substitute for the population analysis, the authentic method for the detection of hetero-VRSA strains.
Abstract: Glycopeptide antibiotics have become the last bastion for the treatment of multidrug-resistant Gram-positive hospital pathogens, the two main ones being methicillin-resistant S. aureus and enterococci. However, in addition to the emergence of vancomycin resistance in enterococci, certain staphylococcal strains with low-level resistance to glycopeptides have increasingly been isolated from clinical specimens. This review focuses on mechanisms of resistance, epidemiology, control measures and therapeutic options for these staphylococci.
Abstract: Two hundred and thirteen clinical strains of coagulase-negative staphylococci isolated in Japan between 1980 and 1997 were analyzed for glycopeptide susceptibility by determining MIC using both Mueller-Hinton agar (MHA) and Brain Heart Infusion agar (BHIA) plates. Of 37 Staphylococcus epidermidis strains isolated between 1980 and 1981, all were susceptible to vancomycin and teicoplanin on both MHA and BHIA. However, of 122 isolates of Staphylococcus epidermidis isolated between 1994 and 1997, 1 (0.8%) was intermediate to vancomycin on MHA and 39 (32%) were intermediate on BHIA, while 3 (2.5%) and 27 (22.1%) were intermediate or resistant to teicoplanin on MHA and BHIA, respectively. It was demonstrated that the susceptibilities of the strains in 1990s to vancomycin and teicoplanin were significantly decreased compared with those in 1980s. Population analysis was performed with six strains each of Staphylococcus epidermidis and Staphylococcus haemolyticus (three with vancomycin MIC > or = 8 micrograms/ml and three with vancomycin MIC < or = 4 micrograms/ml using BHIA). The population curves of the Staphylococcus epidermidis strains showed a homogeneous pattern of susceptibility. Whereas, those for two Staphylococcus haemolyticus strains (vancomycin MIC = 8 micrograms/ml using BHIA) showed a typical heterogeneous pattern. Vancomycin-resistant mutants (MIC > or = 32 micrograms/ml) were obtained with a high frequency of 10(-4)-(-5) from the strains by one-step selection with 16 micrograms/ml of vancomycin.
Abstract: The true nature of resistance of methicillin-resistant Staphylococcus aureus (MRSA) is penicillin-binding protein 2' (PBP2'). Affinities of almost all beta-lactam antibiotics to PBP2' were very low. Therefore, MRSA which produces PBP2' shows resistance to all beta-lactam antibiotics. However, PBP2' has a different affinity to each beta-lactam antibiotic. For this reason, we thought that some derivatives of beta-lactam compounds could have high affinity to PBP2'. Accordingly, we developed cephem compounds which are more stabile and safe than previous penicillin and carbapenem compounds. Firstly, we investigated the side chain at C-7 position on 2-thioisocephem skeletal. Hydroxyimino-aminothiazol at C-7 position on 2-thioisocephem skeletal had the strongest activity against MRSA. Secondly, we investigated the linkage styles at C-3 position on 2-thioisocephem skeletal which were methylene, vinyl, and propylene. The compound of vinyl linkage style at C-3 position on 2-thioisocephem skeletal showed high activity against MRSA. Finally, we investigated 1-thiocephem, 2-thioisocephem, and 2-oxaisocephem as cephem-skeletals. Simultaneously, we studied C-3 linkage styles which were methylene, vinyl, and propylene. From these results, we found out that the compound of hydroxyiminoaminothiazol at C-7 position and vinyl linkage style at C-3 position on 1-thiocephem skeletal has superb activity against MRSA.
Abstract: TOC-50, a new parenteral cephalosporin, was assessed for antibacterial activity in vitro and in vivo. In vitro, the activity of TOC-50 was greater than ampicillin, erythromycin and gentamycin, and was equal to that of imipenem. The MICs of TOC-50 for 90% of the clinical isolates tested (MIC90 values) were 0.0125 microgram/ml for penicillin-susceptible Streptococcus pneumoniae, 0.2 microgram/ml for intermediately penicillin-resistant S. pneumoniae, and 0.39 microgram/ml for fully penicillin-resistant S. pneumoniae. In murine systemic-infection models, TOC-50 had a potent protective activity against penicillin-susceptible of fully penicillin-resistant S. pneumoniae. Its protective activity was stronger than that of imipenem.
Abstract: The antibacterial activity of tazobactam-piperacillin was compared with that of sulbactam-ampicillin, clavulanic acid-ticarcillin, sulbactam-cefoperazone and piperacillin against beta-lactamase-producing bacteria isolated from patients with complicated urinary tract infections. Tazobactam-piperacillin showed a broad antibacterial spectrum against gram-negative and gram-positive bacteria. The minimum inhibitory concentrations (MIC90) of tazobactam-piperacillin were 6.25 micrograms/ml against Escherichia coli, 1.56 micrograms/ml against Proteus mirabilis, 3.13 micrograms/ml against Proteus vulgaris, 6.25 micrograms/ml against methicillin-susceptible Staphylococcus aureus, and 6.25 micrograms/ml coagulase-negative methicillin-susceptible staphylococci. Against all beta-lactamase-producing bacteria tested the antibacterial activity of tazobactam-piperacillin was at least 4- to 64-fold stronger than that of piperacillin, clavulanic acid-ticarcillin, and sulbactam-ampicillin, and similar to or greater than that of sulbactam-cefoperazone except for E. coli.
Abstract: We evaluated a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA), Mu50, for vancomycin susceptibility. Mu50 was isolated from a patient with infection of a surgical incision site which resisted vancomycin therapy. Mu50 showed a decrease in susceptibility to vancomycin, but this strain did not carry vanA or vanB or vanC genes as judged from PCR amplification. MICs of vancomycin against Mu50 and vancomycin-susceptible S. aureus FDA209P, S. aureus ATCC-29213, and MRSA H-1 were 8, 1, 1, and 1 microgram/ml, respectively by agar dilution and macro-broth dilution methods according to NCCLS. MIC values with agar dilution method using MHA + 20% horse serum, HIA, and BHIA agreed with the MIC values with micro- and macro-broth dilution method. Population analysis revealed that vancomycin concentration required for inhibition of ca. 10(7) cells of Mu50, S. aureus FDA209P, S. aureus ATCC29213, and MRSA H-1 were 36, 2, 2, and 2 micrograms/ml, respectively. These results showed that the activity of vancomycin against Mu50 was at least 8-fold decreased compared to that against S. aureus FDA209P, S. aureus ATCC29213, and MRSA H-1.
Abstract: BACKGROUND: Since the discovery of the vancomycin-resistant Staphylococcus aureus (VRSA) strain Mu50 (minimum inhibitory concentration [MIC] 8 mg/L), there has been concern about the potential spread of such strains throughout Japanese hospitals. Two important questions need to be answered: (1) what is the prevalence of VRSA, and (2) by what mechanism does vancomycin resistance occur. METHODS: The vancomycin susceptibilities of three methicillin-resistant S aureus (MRSA) strains (Mu50, Mu3, and H1) and the methicillin-susceptible S aureus type strain FDA209P were compared by MIC determinations and population analysis. Mu3 (MIC 3 mg/L) was isolated from the sputum of a patient with pneumonia after surgery who had failed vancomycin therapy. H1 (MIC 2 mg/L), which is a representative vancomycin-susceptible MRSA strain, was isolated from a patient with pneumonia who responded favourably to vancomycin therapy. Subclones of Mu3 with increased resistance against vancomycin were selected with serial concentrations of vancomycin and their MICs were determined. The prevalence of VRSA and Mu3-like strains in Japanese hospitals was estimated by population analysis from 1149 clinical MRSA isolates obtained from 203 hospitals throughout Japan. The genetic traits of the Mu3 and Mu50 strains were compared with clonotypes of MRSA from around the world. FINDINGS: Mu3 and Mu50 had an identical pulsed-field gel electrophoresis banding pattern. When grown in a drug-free medium, Mu3 produced subpopulation of cells with varying degrees of vancomycin resistance, thus demonstrating natural heterogeneity, or variability, in susceptibility to vancomycin. In the presence of vancomycin, Mu3 produced subclones with resistance roughly proportional to the concentrations of vancomycin used. Selection of Mu3 with 8 mg/L or more of vancomycin gave rise to subclones with vancomycin resistance equal to that of Mu50 (MIC 8 mg/L) at a frequency of 1/1,000,000. During screening of Japanese MRSA strains, no strain of VRSA additional to Mu50 was found. The prevalence of MRSA isolates heterogeneously resistant to vancomycin was 20% in Juntendo University Hospital, 9.3% in the other seven university hospitals, and 1.3% in non-university hospitals or clinics. INTERPRETATION: Heterogeneously resistant VRSA is a preliminary stage that allows development into VRSA upon exposure to vancomycin. Heterogeneously resistant VRSA was found in hospitals throughout Japan. This finding could explain, at least partly, the frequent therapeutic failure of MRSA infection with vancomycin in Japan.
Abstract: The in vitro activity of TOC-50, a new parenteral cephalosporin, was assessed against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE). TOC-50 showed excellent activity, which was stronger than that of methicillin, cloxacillin, the cephalosporins tested, imipenem, gentamycin, minocycline, ofloxacin and ciprofloxacin against MRSA and had a minimum inhibitory concentration (MIC) comparable to that of vancomycin (the MICs of TOC-50 and vancomycin for growth inhibition of 90% of the strains tested were 3.13 and 1.56 micrograms/ml, respectively). Against MRSE, TOC-50 exhibited excellent activity, which was stronger than that of methicillin, ampicillin, the cephalosporins tested and imipenem, and was twice as active as vancomycin. In terms of the bactericidal effect against MRSA, TOC-50 was superior to vancomycin.
Abstract: In vitro and in vivo antibacterial activities of TOC-50, a new parenteral cephalosporin, were assessed against Enterococcus faecalis. In vitro, TOC-50 had excellent activity, stronger than that of penicillin G, sulbactam/ampicillin, tazobactam/piperacillin, the cephalosporins tested, imipenem, vancomycin, gentamicin, tobramycin, arbekacin, amikacin, minocycline and ofloxacin against clinically isolated strains. In addition, TOC-50 was more active than penicillin G, sulbactam/ampicillin and imipenem against vancomycin-resistant E. faecalis NCTC 12201. In terms of bactericidal effect against the same strain, TOC-50 was superior to sulbactam/ampicillin and imipenem. In murine systemic infection models, TOC-50 had a potent protective activity against E. faecalis 42. Its protective activity was stronger than that of imipenem or vancomycin.
Abstract: TOC-39, a new parenteral cephalosporin, is a hydroxyimino-type cephem antibiotic with vinylthio-pyridyl moiety at the 3 position. TOC-39 was evaluated for antibacterial activity against various clinically isolated strains. TOC-39 had excellent activity, stronger than that of methicillin, oxacillin, the cephalosporins tested, imipenem, gentamicin, minocycline, tobramycin, ofloxacin, and ciprofloxacin against methicillin-resistant Staphylococcus aureus (MRSA) and had an MIC comparable to that of vancomycin (the MICs of TOC-39 and vancomycin for 90% of the strains tested were 3.13 and 1.56 micrograms/ml, respectively). Against Enterococcus faecalis strains, which are resistant to cephalosporins, TOC-39 was twice as active as ampicillin. Against methicillin-susceptible S. aureus, coagulase-negative Staphylococcus spp., and Streptococcus pneumoniae, TOC-39 was twice as active as or more active than cefotiam, ceftazidime, flomoxef, and cefpirome. Against Streptococcus pyogenes, TOC-39 was superior to cefotiam, ceftazidime, and flomoxef and was similar to cefpirome. In addition, the activity of TOC-39 was equal to or greater than that of cefotiam, ceftazidime, flomoxef, and cefpirome against Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Morganella morganii. In terms of bactericidal effect against MRSA, TOC-39 was superior to vancomycin. No mutant resistant to TOC-39 or vancomycin was obtained from susceptible MRSA strains. In murine systemic infection models, TOC-39 showed potent activity against S. aureus and E. coli. Against highly MRSA, the activity of TOC-39 was comparable to that of vancomycin.
Abstract: Phosalacine, a new herbicidal antibiotic containing phosphinothricin was isolated from the culture filtrate of a soil isolate Kitasatosporia phosalacinea KA-338. It was a water soluble, amphoteric compound obtained as an amorphous powder (C14H28N3O6P, MW 365). The antibiotic exhibited antimicrobial activity against Gram-positive and Gram-negative bacteria and some fungi on a minimal medium and the activity was reversed by L-glutamine. It also showed herbicidal activity against alfalfa. It is suggested that phosalacine was decomposed to provide phosphinothricin after its incorporation into microbial or plant cells, and exhibited the antimicrobial and herbicidal activities by inhibiting glutamine synthetase with phosphinothricin although phosalacine itself hardly inhibited the enzyme.
