Department of Microbiology

Amongst the soil bacteria one unique group, the Rhizobia have a beneficial effect on the growth of plants. The bacterium within root nodules converts atmospheric nitrogen to ammonia and provides organic nitrogenous compounds to the plants. The symbiotic association between rhizobia and leguminous plants is one of the major contributors to the total biological nitrogen fixation, which is an alternative to the use of nitrogen fertilizers that lead to unacceptable pollution levels. Of the different legumes, one well-known legume of Bangladesh, Dhaincha (Sesbania bispinosa) have generally been considered as an important green manure among the farmers. Thus it was important to study the rhizobial isolate of this less studied legume in order to understand its association to increase soil fertility. The test isolates were previously isolated and characterized and identified through biochemical tests. They gave the correct size amplification product for the nifH gene and nodC gene, which in...

Large plasmid (more than 100 MDa) plays a significant role in Escherichia coli virulence as many virulent genes including the ipaH are encoded by large plasmids. Characterization of such large plasmid of E. coli from different sources based on ipaH gene has not yet been reported with success and credible reproducibility in Bangladesh. Forty E. coli isolates of environmental, clinical, avian, and mammalian sources were examined to detect the presence of large plasmids. Among them, plasmids recovered from 32 isolates were found to range between 100 and 145 MDa in size. Antibiotic susceptibility pattern of the isolates against 17 different  antibiotics showed that most of them were resistant to more than 6 antibiotics and thus were designated multiple antibiotic resistant (MAR) strains. Out of 32 isolates, 10 were (3 clinical, 5 environmental, 1 avian and 1 mammalian source) found to possess a gene product of 423 bp size after PCR assay from plasmid DNA. Southern hybridization was carr...

Introduction: Urinary tract infection is the most frequently diagnosed kidney and urologic disease. Methodology: Whether the Escherichia coli strains responsible for urinary tract infection (UPEC) carry virulence properties of diarrheagenic E. coli (DEC), 56 UPEC strains were examined for the presence of DEC and UPEC characteristics (e.g. biofilm formation, hemolysis activity, virulence genes). Results: Among 56 UPEC strains, 21 showed capable of biofilm formation and only 5 showed hemolysis activity on sheep blood agar. In Multiplex PCR on assessment of virulence genes related to uropathogenesis; 42% was found positive for papC gene, 27% was fim1 positive, 11% was afa positive and none was found positive for sfa. Most of the isolates were found carrying none of eight diarrhea associated genes (e.g. estA, eltB, vt1, vt2, eaeA, ea, ial and bfpA) as expected. Only seven isolates were found to harbor these genes: five genes i.e., vt2, ial, eltB, bfpA and ea were found in five different...

The investigation was carried out to study the characteristics of rhizobial strains isolated from the leguminous plant, Sesbania bispinosa growing in different regions of Bangladesh. Forty-four isolates were studied for biochemical and molecular characteristics. Isolates were able to utilize different carbohydrates. All isolates showed complete resistance to cloxacillin and penicillin G that results in increased survivability of rhizobial populations in antibiotic stressed conditions. Isolates were able to form nodule in the plant infection test. The majority of the strains showed positive results for nodC and nifH gene amplification which are the typical characteristics of Rhizobium species. Genetic relatedness was assessed by comparing the sequences of 16S rRNA. Two distinct clusters were seen in the dendrogram constructed by the Complete Linkage method. The isolates R7, R8, R17, R33 and R3 were distinct from the 20 reference strains. The first cluster was phylogenetically distinc...

Amongst the soil bacteria one unique group, the Rhizobia have a beneficial effect on the growth of plants. The bacterium within root nodules converts atmospheric nitrogen to ammonia and provides organic nitrogenous compounds to the plants. The symbiotic association between rhizobia and leguminous plants is one of the major contributors to the total biological nitrogen fixation, which is an alternative to the use of nitrogen fertilizers that lead to unacceptable pollution levels. Of the different legumes, one well-known legume of Bangladesh, Dhaincha (Sesbania bispinosa) have generally been considered as an important green manure among the farmers. Thus it was important to study the rhizobial isolate of this less studied legume in order to understand its association to increase soil fertility. The test isolates were previously isolated and characterized and identified through biochemical tests. They gave the correct size amplification product for the nifH gene and nodC gene, which in...

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals throughout the world. The endemicity of this disease in Bangladesh has been causing high economic loss and an impediment to the full potential surge of livestock industries. In Bangladesh, vaccination using imported or locally produced FMD vaccines is the existing practice of controlling the disease, although vaccine failure cases are very common. Hence, to address the problem, the present study was envisaged to develop an effective FMD vaccine tailored to the circulating indigenous foot-and-mouth disease virus (FMDV) strains. Three local circulating FMDVs O/BAN/TA/Dh-301/2016 (MK088170.1), A/BAN/CH/Sa-304/2016 (MK088171.1) and Asia1/BAN/DH/Sa-318/2018 (MH457186.1) isolates were selected as vaccine strains based on recent epidemiology, genetic and antigenic analyses. These serotype O, A and Asia1 vaccine strains showed strong antigenic relationship (r1 > 0.3) with 100% to 75% of the respective circulating viruses. The candidate viruses were successfully inactivated by 3.0 mM binary ethylenimine within 7–10 h after the onset of inactivation. Extrapolation of inactivation kinetics confirmed < 1 log10 TCID50 in a 10000-liter batch liquid preparation after 24 h inactivation cycle. The inactivated virus particles were significantly (p < 0.05) concentrated and the trivalent vaccine was formulated using 6 µg per dose per serotype antigen payload. The trivalent vaccine was administered in divided doses in different groups of cattle. All doses of the vaccine elicited significantly (p < 0.05) higher levels of antibodies as early as 14-day post-vaccination (dpv) and peak antibody titers were achieved in 28 dpv. The ‘full dose’ (6.0 µg per dose per serotype) vaccine elicited antibody titers expected to confer protection in 100% cattle of the respective group and maintained such level of antibodies beyond 180 dpv. Thus, the trivalent FMD vaccine prepared with 6.0 µg antigen per dose per serotype of the selected candidate viruses will confer protection against circulating FMDVs of Bangladesh and its neighboring countries.