title: Mexican unpasteurised fresh cheeses are contaminated with Salmonella spp., non-O157 Shiga toxin producing Escherichia coli and potential uropathogenic E. coli strains: A public health risk.
abstract: Fresh cheeses are a main garnish of Mexican food. Consumption of artisanal fresh cheeses is very common and most of them are made from unpasteurised cow milk. A total of 52 fresh unpasteurised cheeses of five different types were purchased from a variety of suppliers from Tabasco, Mexico. Using the most probable number method, 67% and 63% of samples were positive for faecal coliforms and E. coli, respectively; revealing their low microbiological quality. General hygienic conditions and practices of traditional cheese manufacturers were poor; most establishments had unclean cement floors, all lacked windows and doors screens, and none of the food-handlers wore aprons, surgical masks or bouffant caps. After analysing all E. coli isolates (121 strains) for the presence of 26 virulence genes, results showed that 9 (17%) samples were contaminated with diarrheagenic E. coli strains, 8 harboured non-O157 Shiga toxin producing E. coli (STEC), and one sample contained both STEC and diffusely adherent E. coli strains. All STEC strains carried the stx1 gene. Potential uropathogenic E. coli (UPEC) strains were isolated from 15 (29%) samples; the most frequent gene combination was fimA-agn43. Two samples were contaminated with Salmonella. The results demonstrated that unpasteurised fresh cheeses produced in Tabasco are of poor microbiological quality and may frequently harbour foodborne pathogens. Food safety authorities in Mexico need to conduct more rigorous surveillance of fresh cheeses. Furthermore, simple and inexpensive measures as establishing programs emphasizing good hand milking practices and hygienic manufacturing procedures may have a major effect on improving the microbiological quality of these food items.
authors.affiliation: Department of Molecular Biomedicine, CINVESTAV-IPN. Av. IPN #2508, Col. Zacatenco, Mexico City CP 07360, Mexico; Departmento de Microbiología, ENCB-IPN, Prolongación Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Mexico City CP 11340, Mexico.
authors.forename: Rosa
authors.initials: R
authors.lastname: Guzman-Hernandez
authors.affiliation: Departmento de Microbiología, ENCB-IPN, Prolongación Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Mexico City CP 11340, Mexico.
authors.forename: Araceli
authors.initials: A
authors.lastname: Contreras-Rodriguez
authors.affiliation: División de Estudios de Posgrado e Investigación, ITVH, Carretera VHSA-Frontera Km 3.5, Villahermosa, Tabasco, Mexico.
authors.forename: Rosa
authors.initials: R
authors.lastname: Hernandez-Velez
authors.affiliation: Department of Molecular Biomedicine, CINVESTAV-IPN. Av. IPN #2508, Col. Zacatenco, Mexico City CP 07360, Mexico.
authors.forename: Iza
authors.initials: I
authors.lastname: Perez-Martinez
authors.affiliation: Departmento de Microbiología, ENCB-IPN, Prolongación Carpio y Plan de Ayala S/N, Col. Casco de Santo Tomas, Mexico City CP 11340, Mexico.
authors.forename: Ahide
authors.initials: A
authors.lastname: Lopez-Merino
authors.affiliation: Departamento de Investigación, Hospital General O'Horan. Av. Itzaes x Jacinto Canek, Mérida CP 97000, Yucatan, Mexico.
authors.forename: Mussaret B
authors.initials: MB
authors.lastname: Zaidi
authors.affiliation: Department of Molecular Biomedicine, CINVESTAV-IPN. Av. IPN #2508, Col. Zacatenco, Mexico City CP 07360, Mexico. Electronic address: testrada@cinvestav.mx.
authors.forename: Teresa
authors.initials: T
authors.lastname: Estrada-Garcia
mesh_terms: D000818:Animals; D002417:Cattle; D002611:Cheese / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis*; D006801:Humans; D008800:Mexico; D008892:Milk / Q000382:microbiology; D011634:Public Health; D012475:Salmonella / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D022621:Shiga Toxin / Q000378:metabolism; D054323:Shiga-Toxigenic Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D056689:Uropathogenic Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*
chemical_list: D022621:Shiga Toxin
keywords: E. coli genes; Fresh cheeses; Non-O157 STEC; Salmonella; UPEC