Frequency of indicator bacteria, Salmonella and diarrhoeagenic Escherichia coli pathotypes on ready-to-eat cooked vegetable salads from Mexican restaurants

The presence of coliform bacteria, faecal coliforms, Escherichia coli, diarrhoeagenic E.coli pathotypes (DEP) and Salmonella were determined in ready-to-eat cooked vegetable salads (RECS) from restaurants in Pachuca city, Mexico. The RECS were purchased from three types of restaurants: national chain restaurants (A), local restaurants (B) and small restaurants (C). Two restaurants for each A and B, and three for C, were included. Forty RECS samples were purchased at each A and B restaurant and 20 at each C restaurant. Of the overall total of 220 analysed samples, 100, 98.2, 72.3, 4.1 and 4.1% had coliform bacteria, faecal coliforms, E.coli, DEP and Salmonella, respectively. Identified DEP included enteropathogenic E.coli (EPEC), enterotoxigenic E.coli (ETEC) and Shiga toxin-producing E.coli (STEC). The EPEC, ETEC and STEC were isolated each from 1 center dot 4% of samples. No E.coli O157:H7 were detected in any STEC-positive samples. The analysis of Kruskal-Wallis anova and median test of microbiological data showed that the microbiological quality of RECS did not differ between the different restaurants (P>05).