Behaviour of four diarrheagenic Escherichia coli pathotypes on carrots and in unpasteurized carrot juice

The behaviours of Shiga toxin-producing Escherichia coli (STEC), enteroinvasive E.\ua0coli (EIEC), enteropathogenic E.\ua0coli (EPEC) and enterotoxigenic E.\ua0coli (ETEC) strains on raw carrots at 3\ua0±\ua01 and 30\ua0±\ua01°C, and in unpasteurized carrot juice at 3\ua0±\ua01, 12\ua0±\ua01, 20\ua0±\ua01, 30\ua0±\ua01°C and 37\ua0±\ua01°C were determined. Raw carrots were purchased in a local market. Fresh juice was obtained from raw carrots in the laboratory. On whole carrots stored at 30\ua0±\ua01 or 3\ua0±\ua01°C, no growth was observed for any of the diarrheagenic E.\ua0coli pathotype (DEPs) strains studied. After 15\ua0days at 30\ua0±\ua01°C, the tested DEPs had decreased from an initial inoculum level of approximately 6 log colony-forming units (CFU) to approximately 3·5 log CFU on whole carrots, while at 3\ua0±\ua01°C, they decreased from approximately 2·4 log to 1·6 log CFU. All these DEPs grew in fresh carrot juice at 12\ua0±\ua01, 20\ua0±\ua01, 30\ua0±\ua01 and 37\ua0±\ua01°C, reaching counts of approximately 4·2 log, 5·8 log, 6·7 log and 7·5 log CFU\ua0ml-1, respectively, after 24\ua0h. At 3\ua0±\ua01°C, the DEP growth was inhibited at least during 7\ua0days. Thus, storage of carrot juice at unrefrigerated temperatures can result in DEP growth to levels likely to represent a risk to consumers. © 2013 The Society for Applied Microbiology