Survival and characterization of Escherichia coli strains in a typical Mexican acid-fermented food.
In this study, the presence and pathogenic characteristics of Escherichia coli strains in pozol, an acid-fermented maize beverage consumed in South-eastern Mexico, were determined. Seventy-three E. coli strains were isolated at early and late times (6 and 48 h) during the pozol fermentation process, when pH values of the doughs were 6.7-4.7 (6 h) and 4.7-3.7 (48 h). Serotypes that belong to diarrheagenic E. coli serogroups O18, O88, O8, O11, O20, O173 were identified. HEp-2 cell adherence in vitro assays showed localized, diffuse and aggregative adherence patterns among some of these strains. A DNA colony hybridization analysis with different probes showed the presence of virulence genes related to diarrheal pathogenesis. Thirty-three percent of the E. coli strains were tetracycline-resistant and 95% had a 20 kb plasmid. The presence and survival of potentially pathogenic E. coli in acid-fermented pozol suggest that such foods may be a potential source of foodborne outbreaks.
Sainz
T
T
Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, México DF.
Wacher
C
C
Espinoza
J
J
Centurión
D
D
Navarro
A
A
Molina
J
J
Inzunza
A
A
Cravioto
A
A
Eslava
C
C
D001422:Bacterial Adhesion / Q000502:physiology; D001628:Beverages / Q000382:microbiology; D002460:Cell Line; D015169:Colony Count, Microbial; D003967:Diarrhea / Q000382:microbiology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity / Q000502:physiology*; D005285:Fermentation; D005516:Food Microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012703:Serotyping; D014774:Virulence; D003313:Zea mays / Q000382:microbiology*