Education: Ph.D, 2003 Department of Microbiology University of Dhaka, Bangladesh
Diplome de Recherche Specialisee de l’University (DRSU), 1991-1993 (worked at the Pasteur Institute, Paris, France) Department of Biochemistry University of Paris VII, France
M. Phil., 1991 Department of Microbiology University of Dhaka Dhaka, Bangladesh.
M.Sc., 1980 Department of Botany University of Dhaka Dhaka, Bangladesh.
B. Sc. (Hons.), 1978 Botany Department Dhaka University Dhaka, Bangladesh
Past Employment: Associate Scientist, ICDDR,B* (1st May 1992 – 31 December 2004).
a. Assistant Scientist, ICDDR,B (1st September, 1987- 30th April, 1992). b. Senior Research Officer, Clinical Microbiology Section, ICDDR,B (1st October 1986-31st August 1987).
*International Centre For Diarrhoeal Disease Research, Bangladesh
c. Trainer (Research Officer) in ICDDR,B Training Laboratory (26th July 1984 to 30th September 1986):
d. Research Trainee in ICDDR,B (4th July 1981 to 25th July 1984)
Membership in Professional Societies: a). Asiatic Society of Bangladesh, ordinary member (April 2009) b). Bangladesh Society of Genetic Engineering and Biotechnology (Ordibnary member 2008) c). Bangladesh Zoological Society, Life member 2003 (Ordinary member since 1985) d). International Society of Infectious Disease (General member 2001-continues) e). Bangladesh Society for Microbiologists, Life Member 1995 (Ordinary member since 1984) f). Bangladesh Botanical Society, Life Member 1991 (Ordinary member since 1981) g). British Society for General Microbiology (1987-1999). h). Bangladesh Association for Advancement of Science (Ordinary member since 1981)
Awards: French Government Scholarship to work at the Institut Pasteur, Paris, France, May 11, 1991 to September 1993.
British Society for General Microbiology Traval grant to attend First International Workshop on Aeromonas/Plesiomonas, Manchester, England, September 1986
5-6 September 1986 and XIV International Congress of Microbiology, England, September 7-13, 1986.
ICDDR,B Fellowship (Microbiology) from July 1981-july 1994.
National Science and Technology Fellowship from March -June, 1981
Reviewer: a). Journal of Clinical Microbiology, American Sociewty of Microbiology (ASM) Washington, D.C., and b). International Journal of Tuberculosis and Lun Disease, Paris, France.
Over 60 Papers Published in Scientific Journals...
Abstract: Tuberculosis (TB), a highly infectious airborne disease, remains a major global health problem. Many of the new diagnostic techniques are not suited for operation in the highly-endemic low-income countries. A sensitive, fast, easy-to-operate and low-cost method is urgently needed. We performed a Proof of Principle Study (30 participants) and a Validation Study (194 participants) to estimate the diagnostic accuracy of a sophisticated electronic nose (DiagNose, C-it BV) using exhaled air to detect tuberculosis. The DiagNose uses a measurement method that enables transfer of calibration models between devices thus eliminating the most common pitfall for large scale implementation of electronic noses in general. DiagNose measurements were validated using traditional sputum smear microscopy and culture on Löwenstein-Jensen media. We found a sensitivity of 95.9% and specificity of 98.5% for the pilot study. In the validation study we found a sensitivity of 93.5% and a specificity of 85.3% discriminating healthy controls from TB patients, and a sensitivity of 76.5% and specificity of 87.2% when identifying TB patient within the entire test-population (best-case numbers). The portability and fast time-to-result of the DiagNose enables a proactive screening search for new TB cases in rural areas, without the need for highly-skilled operators or a hospital center infrastructure.
Abstract: The oryx bacilli are Mycobacterium tuberculosis complex organisms for which phylogenetic position and host range are unsettled. We characterized 22 isolates by molecular methods and propose elevation to subspecies status as M. orygis. M. orygis is a causative agent of tuberculosis in animals and humans from Africa and South Asia.
Abstract: Despite having 100% coverage of directly observed treatment short-course, multi drug-resistant (MDR) tuberculosis (TB) is still increasing in Bangladesh. Early detection of MDR-TB by rapid molecular test and early initiation of treatment will effectively stop this trend. To develop rapid diagnostic tools, molecular characterization of genes conferring Mycobacterium tuberculosis resistance to rifampicin (RIF) and isoniazid (INH) will be required. Hence, this study elucidated the molecular mechanism RIF and INH resistance in 218 MDR strains from hospitalized (n = 161) and non-hospitalized (n = 57) TB patients in Bangladesh. Mutations in rpoB gene were detected in 207 (95.0%) with majority at codon 531 (52.3%). Mutations in katG or inhA or both were detected in 206 (94.5%) with majority at codon 315 of katG (83.9%). It was noteworthy that a novel C to T mutation at position -34 and G to A mutations at position -47 in inhA regulatory region were found, respectively, in combination with mutation at codon 315 of katG. This is the first comprehensive molecular analysis of rpoB and katG genes and inhA regulatory regions of MDR isolates from Bangladesh. This study provides basic data for the construction of low cost tailor-made molecular system for rapid diagnosis of MDR-TB in Bangladesh.
Abstract: Amino acid substitutions conferring resistance to quinolones in Mycobacterium tuberculosis have generally been found within the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase (GyrA) rather than the B subunit of DNA gyrase (GyrB). To clarify the contribution of an amino acid substitution, E540V, in GyrB to quinolone resistance in M. tuberculosis, we expressed recombinant DNA gyrases in Escherichia coli and characterized them in vitro. Wild-type and GyrB-E540V DNA gyrases were reconstituted in vitro by mixing recombinant GyrA and GyrB. Correlation between the amino acid substitution and quinolone resistance was assessed by the ATP-dependent DNA supercoiling assay, quinolone-inhibited supercoiling assay, and DNA cleavage assay. The 50% inhibitory concentrations of eight quinolones against DNA gyrases bearing the E540V amino acid substitution in GyrB were 2.5- to 36-fold higher than those against the wild-type enzyme. Similarly, the 25% maximum DNA cleavage concentrations were 1.5- to 14-fold higher for the E540V gyrase than for the wild-type enzyme. We further demonstrated that the E540V amino acid substitution influenced the interaction between DNA gyrase and the substituent(s) at R-7, R-8, or both in quinolone structures. This is the first detailed study of the contribution of the E540V amino acid substitution in GyrB to quinolone resistance in M. tuberculosis.
Abstract: Five Mycobacterium tuberculosis isolates were obtained from three body sites from a Dutch patient. The isolates displayed a single genotype by 24-locus MIRU-VNTR typing (except for a single locus not amplified from one isolate) but were differentiated by small variations in IS6110 fingerprints, spoligotypes, 6 hypervariable MIRU-VNTR loci, and/or DiversiLab profiles, revealing patterns of microevolution in a clonal infection.
Abstract: Species identification of isolates belonging to the Mycobacterium tuberculosis complex (MTC) seems to be important for the appropriate treatment of patients, since M. bovis is naturally resistant to a first line anti-tuberculosis (TB) drug, pyrazinamide, while most of the other MTC members are susceptible to this antimicrobial agent. A simple and low-cost differentiation method was needed in higher TB burden countries, such as Bangladesh, where the prevalence of M. bovis among people or cattle has not been investigated.
Abstract: Spread of drug-resistant tuberculosis (TB) threatens TB-control programmes, and all countries need to monitor the patterns and trends of anti-TB drug resistance. Such data assess the quality of control programmes and help forecast future trends of drug resistance. It will also help to establish guidelines for TB therapy. The aim of the current study was to describe the rate of drug-resistant Mycobacterium tuberculosis in the Sunamganj District of Bangladesh. Bacterial isolates were collected from sputum smear positive (ss+) patients who attended the National TB Programme from November 2003 to December 2004. A total of 95 isolates was tested for susceptibility to streptomycin (SM), isoniazid (INH), rifampicin (RMP) and ethambutol (EMB) at the National Reference Laboratory for Mycobacteria at the Norwegian Institute of Public Health (NIPH), Oslo. The total resistance among new cases to any drug was 31%. For SM it was 18%, INH 23%, RMP 2%, EMB 10% and 2% were multidrug-resistant (MDR). The National Tuberculosis Programme (NTP) in Sunamganj is still effective, although the high resistance to INH is alarming. An increased risk of treatment failure has been demonstrated in areas with high levels of INH resistance, and a high proportion of INH resistant cases may develop resistance to RMP during treatment.
Abstract: The characteristics of loop-mediated isothermal amplification (LAMP) make it a promising platform for the molecular detection of tuberculosis (TB) in developing countries. Here, we report on the first clinical evaluation of LAMP for the detection of pulmonary TB in microscopy centers in Peru, Bangladesh, and Tanzania to determine its operational applicability in such settings. A prototype LAMP assay with simplified manual DNA extraction was evaluated for accuracy and ease of use. The sensitivity of LAMP in smear- and culture-positive sputum specimens was 97.7% (173/177 specimens; 95% confidence interval [CI], 95.5 to 99.9%), and the sensitivity in smear-negative, culture-positive specimens was 48.8% (21/43 specimens; CI, 33.9 to 63.7%). The specificity in culture-negative samples was 99% (500/505 specimens; CI, 98.1 to 99.9%). The average hands-on time for testing six samples and two controls was 54 min, similar to that of sputum smear microscopy. The optimal amplification time was 40 min. No indeterminate results were reported, and the interreader variability was 0.4%. Despite the use of a single room without biosafety cabinets for all procedures, no DNA contamination was observed. The assay was robust, with high end-point stability and low rates of test failure. Technicians with no prior molecular experience easily performed the assay after 1 week of training, and opportunities for further simplification of the assay were identified.
Abstract: Mycobacterial colonies of two different morphologies were isolated from one sputum sample of a HIV-positive patient. One morphological type was resistant to streptomycin (STR) and susceptible to isoniazid (INH), while the other isolate with different colony morphology was resistant to both of these anti-TB drugs. A mycobacterial isolate of one pus from a lymph node sample was resistant to these two anti-TB drugs, while the other isolate from another pus sample was resistant to STR but susceptible INH. IS6110 RFLP based finger printing revealed that the HIV-positive patient was infected with different strains of Mycobacterium tuberculosis. A subculture of isolates on solid medium is useful to examine mixed infection.
Abstract: Acid-fast bacilli (AFB) were detected in the autopsy lung tissue homogenate samples of four cows (variety Frisian cross) in a dairy farm in Bangladesh. Histopathological examination of the lung tissue demonstrated prominent granulomas, caseating necrosis and calcification indicative of tuberculosis (TB) infection. Mycobacteria could not be cultured from the tissue homogenate samples by Lowenstein-Jensen based conventional culture method though AFB were evident by Ziehl-Neelsen (ZN) staining of the smears of tissue homogenate and in paraffin embedded tissue slices. Spoligotyping performed on DNA extracts of paraffin embedded lung tissue samples confirmed the AFB as a member of the M. tuberculosis complex (MTBC) with a pattern assigned to M. africanum subtype I. This characterization by spoligotyping was confirmed by subjecting M. africanum subtype I isolates from other parts of the world to an alternative identification method based on DNA polymorphism in the gyrB gene (Hain Life Science, GmbH, Nehren, Germany). Since M. africanum is believed to be a human pathogen, general infection in cattle may be a public health threat. The presence of these bacteria in the animal reservoir most likely originated from a caretaker.
Abstract: Spoligotyping was performed to study the population structure of Mycobacterium tuberculosis complex strains (n = 224) from Bangladesh. Strains were split into principal genetic group 1 (PGG 1 [75.0%]) and PGG 2 and 3 (25%). Forty-nine strains with a new spoligotype signature and considered as south or southeast Asian-linked emerging clones were designated as "Matlab type."
Abstract: A total of 111 Mycobacterium tuberculosis isolates from new pulmonary tuberculosis patients, living in the rural Sunamganj district in northern Bangladesh were characterized with IS6110 restriction fragment length polymorphism analyses and spoligotyping. Only 3 of the isolates belonged to the W-Beijing genotype of M. tuberculosis. A high degree of diversity indicated that the spread of M. tuberculosis, in this rural area, was not caused by closely related genotypes. The tuberculosis cases in the current study were less likely to represent recent transmission than what is commonly observed in urban parts of south-east Asia. It was indicated that the tuberculosis cases of this isolated area, of a high-incidence country, represented those of an established epidemic, not yet influenced by recently disseminated strains.
Abstract: The Direct Repeat locus of the Mycobacterium tuberculosis complex (MTC) is a member of the CRISPR (Clustered regularly interspaced short palindromic repeats) sequences family. Spoligotyping is the widely used PCR-based reverse-hybridization blotting technique that assays the genetic diversity of this locus and is useful both for clinical laboratory, molecular epidemiology, evolutionary and population genetics. It is easy, robust, cheap, and produces highly diverse portable numerical results, as the result of the combination of (1) Unique Events Polymorphism (UEP) (2) Insertion-Sequence-mediated genetic recombination. Genetic convergence, although rare, was also previously demonstrated. Three previous international spoligotype databases had partly revealed the global and local geographical structures of MTC bacilli populations, however, there was a need for the release of a new, more representative and extended, international spoligotyping database.
Abstract: The magnitude of anti-tuberculosis drug resistance in Bangladesh is not precisely known. We studied the drug resistance patterns of Mycobacterium tuberculosis in an urban and a rural area of Bangladesh. A tuberculosis (TB) surveillance system has been set up in a population of 106,000 in rural Matlab and in a TB clinic in urban Dhaka. Trained field workers interviewed all persons > or =15 y at Matlab to detect suspected cases of tuberculosis (cough >21 d) and sputum samples were examined for acid-fast bacilli (AFB). The first 3 AFB positive patients daily from the urban clinic were included. AFB positive cases diagnosed between June 2001 and June 2003 from both settings were cultured and drug susceptibility tests were performed. Of 657 isolates, resistance to 1 or more drugs was observed in 48.4% of isolates. Resistance to streptomycin, isoniazid, ethambutol and rifampicin was observed in 45.2%, 14.2%, 7.9% and 6.4% of isolates, respectively. Multidrug resistance was observed in 5.5% of isolates. It was significantly higher among persons who previously had received tuberculosis treatment of > or =1 month (15.4% vs 3.0%, adjusted OR: 6.12, 95% CI: 3.03-12.34). The magnitude of anti-tuberculosis drug resistance in Bangladesh is high. Further evaluation is needed to explain the high proportion of streptomycin resistant M. tuberculosis. Appropriate measures to control and prevent drug resistant tuberculosis in Bangladesh to reduce mortality and transmission are warranted.
Abstract: We have previously demonstrated that Mycobacterium bovis BCG-specific immunoglobulin G antibodies in lymphocyte secretions (ALS) can be employed as a marker for active tuberculosis (TB). We aimed to determine whether the ALS method allows detection of subclinical TB infection in asymptomatic individuals. A prospective study of family contacts (FCs) of patients with active TB and healthy controls was performed. Thirteen of 42 FCs had high ALS responses, including 6 FCs who subsequently developed active TB. No correlation was observed between the tuberculin skin test and the ALS responses in the FCs (r = 0.1, P = 0.23). Among patients with active TB, BCG-specific ALS responses steadily declined from the time of diagnosis through 6 months following antimycobacterial chemotherapy (P = 0.001). The ALS assay enabled detection of infection in exposed symptom-free contacts, who are at greater risk for developing active TB. The method may also allow discrimination between effective treatment of active infection and suboptimal response to therapy.
