Presence of indicator bacteria, Salmonella and diarrheagenic Escherichia coli pathotypes on mung bean sprouts from public markets in Pachuca, Mexico

Coliform bacteria (CB), fecal coliforms (FC), Escherichia coli, diarrheagenic E. coli pathotypes (DEP) and Salmonella frequencies were determined for mung bean (Vigna radiata) sprouts. One hundred sprout samples were collected from markets in Pachuca, Hidalgo state, Mexico. Of these samples, 100% were positive for CB, 98% for FC, 95% for E. coli, 10% for DEP and 5% for Salmonella. Identified DEP included enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC) and Shiga toxin-producing E. coli (STEC). The ETEC and EIEC were each isolated from 2% of samples, and the STEC from 6% of samples. No E. coli O157:H7 were detected in any STEC-positive samples. Positive correlations were observed between FC and E. coli and between E. coli and DEP. A negative correlation occurred between CB and DEP, and between CB and Salmonella. Neither FC nor E. coli correlated with Salmonella presence in the sprout samples. This is the first report of ETEC, EIEC and STEC isolated from sprouts in Mexico and the first report of Salmonella isolation from mung bean in Mexico. Mung bean sprouts are very probably an important factor contributing to the endemicity of ETEC, EIEC and STEC and Salmonella-related gastroenteritis in Mexico.