RESUMO
A quantitative survey of Clostridium perfringens in typical foods served at local restaurants was conducted for 18 months in Guadalajara, Mexico. A total of 151 samples, including goat's birria (50), pozole (50), and beef tamales (51), were collected from small restaurants in Guadalajara. Samples were tested for C. perfringens by the most probable number (MPN) method and for mesophilic aerobic plate counts (MAPCs) and coliform, yeast, and mold counts by plate count methods. Isolates confirmed as C. perfringens were further sporulated and tested for cytotoxic or cytotonic effect against Vero cells as an indication of enterotoxin production. C. perfringens was detected in 78 (52%) of all samples at concentrations that ranged from 2.3 to 5.4 log MPN/g. Average MAPCs were 1.3 to 2.7 log CFU/g, depending on the type of dish. Coliform counts ranged from less than 1.0 to 1.5 CFU/g, and yeast and mold counts were less than 1.0 log CFU/g in all cases. A total of 118 isolates of C. perfringens were tested for enterotoxic effect on Vero cells; 82 (70%) showed activity against Vero cells. Of them, 31 isolates induced cell lysis, indicating cytotoxic effect; 41 induced cell elongation, indicating cytotonic effect; and 10 produced both cytotoxic and cytotonic effect. Dilution of the bacterial filtrates that were still producing an effect on Vero cells ranged from 1:80 to 1:5,120. These results underscore the importance of determining enterotoxigenicity when testing for C. perfringens in foods.
Assuntos
Clostridium perfringens/isolamento & purificação , Qualidade de Produtos para o Consumidor , Contaminação de Alimentos/análise , Manipulação de Alimentos/métodos , Produtos da Carne/microbiologia , Animais , Bovinos , Chlorocebus aethiops , Clostridium perfringens/metabolismo , Clostridium perfringens/patogenicidade , Contagem de Colônia Microbiana , Enterotoxinas/biossíntese , Microbiologia de Alimentos , Cabras , Humanos , México , Temperatura , Células VeroRESUMO
Diez cepas de cada uno de los generos Streptococcus, Lactobacillus y Leuconostoc, fueron aisladas de quesos frescos no pasteurizados del comercio, y determinada su capacidad para antagonizar 13 cepas de Staphylococcus aureus, 13 de Salmonella (3 serotipos) y 13 de Shigella (dysenteriae, flexneri, sonnei y boydii). El efecto antagonico se determino con base a la capacidad para inhibir el desarrollo del patogeno sobre placa de agar APT inoculada con la bacteria lactica. Los primeros se probaron a dos niveles: aproxidadamente 4 veces mayor y 30 veces menor que la del lactico en las zonas de contacto. Todas las cepas se mostraron muy activas excepto 4 de Lactobacillus, con nulo efecto hacia las 33 de patogenos, y 2 de Leuconostoc que resultaron ineficientes contra las 13 de Shigella. El Streptococcus presento la mayor y mas consistente capacidad antagonista incluidos los inoculos altos del patogeno. Entre estos, las cepas de Shigella (con la salvedad anotada) exhibieron la mayor susceptibilidad. La manifiesta capacidad antagonista de las bacterias lacticas que forman parte de la flora natural de la leche cruda, contribuye a explicar el limitado papel de los quesos frescos no pasteurizados en la incidencia directa de gastroenteritis en la poblacion