Tasmina Rahman

Microbiological analysis of common preservatives used in food items and demonstration of their in vitro anti-bacterial activity

Abstract Objective To quantify the microorganisms contaminating the common preservatives used in food as well as to detect their in vitro anti-bacterial traits. Methods A total of 9 preservatives were subjected to conventional cultural and biochemical methods for microbial enumeration. Anti-bacterial activities were demonstrated through the agar well diffusion method. Results All samples were found to be contaminated with bacteria up to 105 CFU/g and with the fungal flora within a range of 101−102 CFU/g. Escherichia coli, Pseudomonas spp. and Staphylococcus spp. were demonstrated in most of the samples. Sodium sulfite and citric acid possessed the strongest anti-bacterial trait against all of the test bacteria. Acetic acid exhibited activity against 6 out of 8 test bacteria while vinegar exhibited the activity against 4 bacteria. Activity of salt was demonstrated only against Listeria spp. and Bacillus spp., while activity of sugar and honey was found only against Escherichia coli and Klebsiella spp., respectively. Conclusions According to the current investigation, sodium sulfite and citric acid samples were found to be satisfactory preservatives both in terms of microbiological criteria and their anti-bacterial traits.

Analysis of Immune Responses and Serological Cross Reactivities among Vibrio cholerae O1, Shigella flexneri 2a and Haemophilus influenzae b

Antigenic determinants expressed on the bacterial cell surface are of importance in the serological characterization and microbiological diagnosis. The bacterial strains carrying these identical or similar antigenic epitopes might react with antibodies produced against other strains. In this study, strong immunogenicity and antigenic cross reactivity were demonstrated among V. cholerae O1, S. flexnerii 2a and H. influenzae b surface components. The enzyme linked immunosorbent assay (ELISA) results were supported by Western blot analysis, where at least 20 antigenic bands, were obtained in each of the reactions, when the surface components were reacted with the homologous antisera. The indirect ELISA results also demonstrated high degree of antigenic relatedness between the surface components of these species, where each surface component was reacted with the heterologous antisera. Western blot analysis also revealed cross reactions between the surface components suggesting common distribution of antigens/epitopes in these bacterial species. This study, thus, gave a clear idea of the level of antigenic sharing and variations among the pathogenic V. cholerae O1, S. flexneri 2a and H. influenzae b strains, which in future, may help in selecting a proper candidate for vaccines and immunodiagnostics development.

Study of microbial proliferation and the in vitro antibacterial traits of commonly available flowers in Dhaka Metropolis

Abstract Objective To examine the prevalence of microorganisms and the antibacterial feature within commonly available flowers including Hibiscus rosa-sinensis, Ixora coccinea, Ipomoea digitata, Allamanda cathartica, Nymphaea nouchali and Vinca rosea , samples were randomly collected from different areas in Dhaka city, Bangladesh. Methods Conventional cultural and biochemical methods were applied to isolate and enumerate the flower accessing microorganisms. Flower extracts were prepared using the solvent extraction methods and the subsequent antibacterial activities were demonstrated. Results The total bacterial load and fungal load was estimated to be around 10 7 -10 8 CFU/g and 10 5 -10 7 CFU/g, respectively. All samples were found to be shaded with Staphylococcus spp. (˜10 7 CFU/g) while the prevalence of actinomycetes was also observed except for Ipomoea digitata . The prevalence of Gram negative pathogenic bacteria was also noted within more than 50% samples. The in vitro antibacterial activity of these flowers, especially of Ixora coccinea, Hibiscus rosa-sinensis, Allamanda cathartica and Nymphaea nouchali in alcoholic extracts (methanol and ethanol) was notable against most of the tested microorganisms. Conclusions The contaminating microbial flora identified within the flower samples studied could be a potential environmental hazard if disseminated. Conversely the revealed antibacterial traits of the flower extracts would be useful alternate remedies of the synthetic drugs for disease medication.