The Minimum Growth Temperatures of Shiga Toxin-Producing Escherichia coli

The objective of this study was to determine the minimum growth temperature of Shiga toxin-producing Escherichia coli (STEC). Forty-eight strains of STEC, including E. coli O157:H7, O104:H4, O26, O45, O103, O111, O121, and O145, were inoculated into tryptic soy broth (TSB) at ca. 6.0 CFU/mL and incubated at temperatures ranging from 5°C to 11°C. The lowest temperature at which growth occurred was determined as the minimum growth temperature of the strain. The minimum growth temperature varied among strains, but the strain difference was within 2-3°C. All of the STEC strains grew at ≥10.3°C. Majority of the STEC strains (31/48) grew at 8.9°C, with some strains (10/48) being able to grow at as low as 8.0°C. None of the STEC serogroups were able to grow at ≤7.4°C. E. coli O104:H4 and O157:H7 had relatively lower minimum growth temperatures, with 8°C and average 8.4°C, respectively, whereas serogroup O26 had a higher minimum growth temperature (average 9.6°C). The results of this study provide basic but critical information on STEC growth and could be used either in fundamental research or to mitigate the risk of STEC from food products by storing them at temperatures below the minimal growth temperature.