Analysis of microbial contamination levels of fruits and vegetables at retail in Monterrey, Mexico

Many fresh produce items including melons, parsley, onions, tomatoes and jalapeño and serrano peppers, have been linked to outbreaks of microbial disease. Little is known about the quality of fresh produce in the northern part of Mexico. Monterrey, situated in northeast Mexico, is the third largest city in the country, with a population of about four million inhabitants. In this study, a total of 300 samples were analyzed. Levels of coliform and total viable counts were analyzed using the TEMPO® automated system. The miniVidas® system was used for the detection of Salmonella spp., E. coli O157:H7, L. monocytogenes and C. jejuni/coli/lari. The presence of C. perfringens and Shigella spp. was determined according to the methodology described in the BAM (FDA, USA).The level of mold and yeast was analyzed according to Mexican regulations. Levels of mesophilic organisms ranged from 10 to > 10⁷ CFU/g. Coliforms, molds and yeasts exhibited levels below 10⁵ CFU/g in most samples, with tomatoes exhibiting the lowest levels. Clostridium perfringens was isolated from six samples of parsley, and Salmonella Typhi, Campylobacter spp. and L. monocytogenes were each isolated mostly from one different parsley sample. Neither E. coli O157:H7 nor Shigella spp. were detected in any samples.