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Articles by Ishrat Sultana
Total Records ( 3 ) for Ishrat Sultana
  Ishrat Sultana , Rahman Md. Mizanur , Shakhawat Hossain Bhuiyan and Md. Majibur Rahman
  This study relates to the survivality of Shigella dysenteriae and S. flexneri in acid environment and the effect of salt induction on subsequent sensitivity to acid. After 120 min exposure to acidic environment at pH 3, around 30% survivality of both the Shigella spp. was recorded. The acid tolerance was found to be dependent on the growth phase and the pH of the growth medium. Shigella spp. previously grown in low-salt broth at pH 7.2, produced organisms which were markedly more acid sensitive when subsequently cultured in the same broth supplemented with 200 mM or more salt at 37 °C. However The 0 degree of sensitivity varied with the time of exposure in different salts. Almost no viable cells were recorded after 30 min exposure when treated with 500 mM salt at pH 3. Survivality of salt treated Shigella spp. was also found to be influenced by different water samples. Viable counts could be observed up to 6 days in normal saline, where as, in pond-, tap- and distilled water Shigella spp. were not detected after 96, 72 and 72 h respectively. Shigella spp. treated with 500 mM salt went into non-culturable state but remain viable as was detected by acridine orange staining method. No significant changes of the virulence properties of NaCl treated Shigella spp. was noted.
  Ishrat Sultana , Rahman Md. Mizanur , Shakhawat Hossain Bhuiyan and Md. Majibur Rahman
  Acids and salts are important environmental conditions encountered by Shigella spp. during its survivality and pathogenesis. These studies have shown that S. sonnei and S. boydii could survive longer than 120 min to acidic environment at pH 3 and approximately 32% survivality for both the species was recorded. The acid tolerance was found to be dependent on the growth phase and pH of the growth medium. Shigella spp. previously grown in low-salt broth at pH 7.2, produced organisms which were markedly more acid sensitive when subsequently cultured in the same broth supplemented with 200 mM or more salt at 37 °C. A differential survival pattern was recorded with salt-treated Shigella spp. in a number of aquatic samples. Fluorescent microscopic examination revealed that Shigella spp. treated with 500 mM salt went into non-culturable state but remain viable. However, salt treatment could produce no significant changes to the infective properties of Shigella spp.
  Rahman Md. Mizanur , Sirajul Islam Khan , Mohammad Sirajul Islam , Ishrat Sultana , Zeaur Rahim and M. J. Albert
  Bacterial chemotaxis is one of the important mechanisms of association of bacteria and other living biota. To investigate the role of chemotaxis that might function for association of Vibrio cholerae -0139 with different aquatic flora and fauna, the homogenates of four aquatic plants and animals namely water hyacinth (Eichhornia crassipes), water cress (Pistia stratiotes), oyster (Lamellidens marginalis) and snail (Pila globosa) were examined in chemotaxis capillary assay. Chemotaxis assay revealed that V. cholerae -0139 swims towards the homogenates of aquatic plants and animals with a higher chemotactic response being observed for 4% solution of P. globosa homogenate. The influence of temperature and salinity on the chemotaxis of V. cholerae -0139 revealed that at 250C and 1.7% salinity favoured the chemotactic motility towards the homogenates of aquatic flora and fauna. Vibrio cholerae -01 also showed the chemotactic response to the homogenates of snail muscles.
 
 
 
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