Effect of Sodium Chloride, pH and Temperature on Growth of Shigella flexneri.

A systematic study of the effect of sodium chloride (0.5, 2.0, 3.5, 5.0%), pH (7.5, 6.5, 5.5), and temperature (37, 28, 19, 10°C) on growth of Shigella flexneri is reported for the first time, using a factorial design. Experiments were done using Brain-Heart Infusion media inoculated to contain 1 × 103 cfu/ml and incubated on rotary shakers (150 rpm). Growth curves were plotted from the experimental data by means of the Gompertz equation, and growth rates, lag times, generation times, and maximum populations were derived for all variable combinations. Results indicated that the three variables interact to affect the growth of S. flexneri , and combinations of low temperature, low pH, and high sodium chloride contents are strongly inhibitory.