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Catfish Special Issue: Growth of Non-O157:H7 Shiga-Toxin Producing Escherichia Coli on Catfish Fillets

Parvaneh Khosravi, Juan Silva, Christopher H. Sommers and Shiowshuh Sheen

Shiga-toxin producing Escherichia coli (STECs) are emerging pathogens which have been involved in numerous foodborne illness outbreaks. In this study the ability of a multi-isolate cocktail of STEC serovars O26:H11, O45:H2, O103:H2, O111: NM, O121:H19, and O145:RM to grow on catfish fillets at refrigeration and abuse temperatures was investigated. Catfish fillet samples (10 g) were inoculated with the STEC cocktails to ca. 3 log CFU/g and incubated under aerobic conditions for up to 120 hrs. There was no STEC growth at 4°C, however, the STECs grew at 10, 15, 20 and 30°C in a temperature dependent manner, with higher growth rate being associated with higher temperature. Lag phase ranged from 15 h at 10°C to 1.75 h at 30°C. Exponential phase growth rate ranged from 0.03 log CFU/g/h at 10°C to 0.65 log CFU/g/h at 30°C. Growth curves constructed using ComBase DMfit provided a good statistical fit to the observed data, resulting in a high correlation coefficient (R2) of 0.98. The results of this study provide information to risk assessors regarding the growth potential of the STECs on aquaculture-raised fish using catfish as a model system.