title: Acid and alcohol tolerance of Escherichia coli O157:H7 in pulque, a typical Mexican beverage.
abstract: Pulque is a traditional Mexican fermented alcoholic beverage produced from the nectar of maguey agave plants. No data exist on the behavior of Escherichia coli O157:H7 in agave nectar and pulque. An initial trial was done of the behavior of E. coli O157:H7 during fermentation of nectar from a single producer, a nectar mixture from different producers and "seed" pulque. A second trial simulating artisanal pulque production was done by contaminating fresh nectar with a cocktail of three E. coli O157:H7 strains, storing at 16 ° and 22 °C for 14 h, adding seed pulque and fermenting until pulque was formed. A third trial used pulque from the second trial stored at 22 °C as seed to ferment fresh nectar at 22 °C for 48 h (fermentation cycle). This procedure was repeated for an additional two fermentation cycles. During incubation at 16 ° or 22 °C in the first trial, the E. coli O157:H7 strains multiplied in both the single producer nectar and nectar mixture, reaching maximum concentration at 12h. E. coli O157:H7 cell concentration then decreased slowly, although it survived at least 72 h in both fermented nectars. E. coli O157:H7 did not multiply in the seed pulque but did survive at least 72 h. In the second trial, the numbers of E. coli O157:H7 increased approximately 1.5 log CFU/ml at 22 °C and 1.2 log CFU/ml at 16 °C after 14 h. After seed pulque was added, E. coli O157:H7 concentration decreased to approximately 2 log CFU/ml, and then remained constant until pulque was produced. In the third trial, the E. coli O157:H7 cells multiplied and survived during at least three nectar fermentation cycles. The results suggest that E. coli O157:H7 can develop acid and alcohol tolerance in pulque, and constitutes a public health risk for pulque consumers.
authors.affiliation: Centro de investigaciones Químicas, Instituto de Ciencias Básicas e Ingeniería, Universidad Autónoma del Estado de Hidalgo, Centro Universitario, Carretera Pachuca-Tulancingo Km. 4.5, 42183 Mineral de la Reforma, Hidalgo, Mexico.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Gómez-Aldapa
authors.forename: Claudio A
authors.initials: CA
authors.lastname: Díaz-Cruz
authors.forename: Angelica
authors.initials: A
authors.lastname: Villarruel-López
authors.forename: M
authors.initials: M
authors.lastname: Del Refugio Torres-Vitela
authors.forename: Esmeralda
authors.initials: E
authors.lastname: Rangel-Vargas
authors.forename: Javier
authors.initials: J
authors.lastname: Castro-Rosas
mesh_terms: D000143:Acids; D027882:Agave; D000434:Alcoholic Beverages / Q000382:microbiology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004926:Escherichia coli; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D000431:Ethanol; D005285:Fermentation; D005506:Food Contamination; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D008800:Mexico; D057048:Plant Nectar; D011634:Public Health; D013696:Temperature
chemical_list: D000143:Acids; D057048:Plant Nectar; D000431:Ethanol