Presence of coliform bacteria, fecal coliforms, Escherichia coli and Salmonella on corn tortillas in central Mexico

Corn tortillas are a primary foodstuff in Mexico with nearly 12 million tons produced and consumed annually. Federal health regulations control tortilla production and sale in Mexico, but most producers do not fully implement them. No data are currently available on microbiological quality or presence of pathogenic bacteria on tortillas produced in Mexico or other countries. Analyses of coliform bacteria (CB), fecal coliforms (FC), Escherichia coli and Salmonella frequency were done on corn tortillas. Tortilla samples were collected from small-scale producers called tortillerías. Two hundred samples (500 g) were acquired at tortillerías in five municipalities in Hidalgo State, Mexico. CB were detected on 70% of samples, FC on 40%, E. coli on 32% and Salmonella on 2%. In positive samples, CB concentration ranged from 1 × 101 to 1 × 106 CFU/g, and FC and E. coli concentrations from 3 to 1100 MPN/g. CB, FC and E. coli presence and concentration all correlated well with Salmonella presence in tortilla. The analysis of Kruskal-Wallis ANOVA and median test of microbiological data showed that the microbiological quality of tortilla samples did not differ between the different tortillerías. In addition, CB, FC and E. coli all correlated well with Salmonella presence in tortilla.This is the first report of microbiological quality of corn tortillas and Salmonella isolation from tortillas in Mexico. Corn tortillas could be a potential source of enteropathogenic bacteria as Salmonella.