Recovery of low-temperature stressed E. coli O157:H7 and its susceptibility to crystal violet, bile salt, sodium chloride and ethanol

This study was conducted to investigate the alteration of some characteristics of E. coli O157:H7 subjected to various periods of storage at -5, -18 and -28 degrees C. Results revealed that the low-temperature treatments increased the susceptibility of E. coli O157:H7 to crystal violet, bile salt, sodium chloride and ethanol. In general, the susceptibility of E. coli O157:H7 subjected to storage at -18 degrees C increased most significantly. The susceptibility of E. coli O157:H7 to the tested agents increased as the period of low-temperature storage extended, regardless of storage temperature. Among the various nitrogen and carbon sources tested, tryptone and soytone were the most effective nitrogen sources, while glucose and maltose were the most effective carbon sources for the growth of the low-temperature stressed cells. When growing the stressed E. coli O157:H7 in media containing the same nitrogen source or carbon source, their lag period increased as the time of frozen storage increased. It was also noted that in general, the recovery of the low-temperature stressed E. coli O157:H7 was highest on tryptic soy agar followed by Modified eosin methylene blue agar, while recovery on MaConkey sorbitol agar and Modified MaConkey sorbitol agar was lowest.