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Year : 1998  |  Volume : 16  |  Issue : 4  |  Page : 169-174

factors affecting hemolysin expression and its associated characteristics in S. Typhimurium and S. Typhi


Department of Microbiology, Panjab university, Chandigarh

Correspondence Address:
MK Uppal
Department of Microbiology, Panjab university, Chandigarh

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ABSTRACT: Human clinical isolates (n=29) of S. typhi and S. typhimurium were screened for hemolysis and found weekly hemolytic under aerobic conditions and strongly hemolytic under microaerophilic conditions. S. typhimurium (his) mutants (n=4) remained weakly hemolytic even under microaerophilic conditions. Hemolytic activity in salmonellae was found to be thermoregulated and chromosome mediated. Addition of iron-chelator to growth medium was inhibitory to hemolysin activity and to congo red dye binding at 37 degree C. S. typhimurium cell adherence to enterocytes was more to the posterior portion of small intestine. Minor differences were observed in phagocytic uptake and intracellular survival rates of S. typhimurium 98 and S. typhimurium TA 98 (mutant). The up regulation in growth of both the phagocytosed bacteria was observed upto 3 hours and thereafter drop in bacterial number was seen. Acid Tolerance Response was higher in adapted cell (pH 5.8) as compared to the unadapted cells (pH 7.2) shifted to pH 3.3. In view of these findings, the hemolysin activity in S. typhimurium appeared to be critical for lysis of phagocytic vacuole where they survive acidic conditions and multiply after invasion of epithelial cells which they penetrate for intracellular survival.






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