Comparison of Recovery Levels of Shigella sonnet ATCC 29930 Treated at Different NaCl Concentrations after Sublethal Heating

摘要

The viability of Shigella sonnei, a significant cause of gastroenteritis in Korea, on ISA plates was determined after sublethal heating treatments and NaCl treatments. In addition, recovery levels of sublethally injured cells on ISA plates containingdifferent concentrations of NaCl (TSAS) were investigated. The viability decreased significantly with increasing degree of sublethal heating treatments, but increases in NaCl treatment concentration from 0 to 6% had little effect on the viability. Afterbeing sublethally treated at 55 deg C for 30 min, bacterial populations were reduced by 7.58, 7.83 and 7.93 log CFU/mL on 2, 4, and 6% TSAS, respectively. After being sublethally treated at 60 deg C for 30 min, bacterial populations were reduced by 6.71,6.73, and 6.73 log CFU/mL on 2, 4 and 6% TSAS, respectively. Decimal reduction times (D-values) decreased with increasing NaCl treatment concentrations after sublethal heating at 55 or 60 deg C. These data imply that the S. sonnei cells sublethally injured by insufficient heating processes had a lower recovery rate with increasing NaCl concentrations in the recovery media.