Incidence and behavior of Salmonella and Escherichia coli on whole and sliced zucchini squash (Cucurbitapepo) fruit.

The incidence of coliform bacteria (CB), thermotolerant coliforms (TC), Escherichia coli, and Salmonella was determined for zucchini squash fruit. In addition, the behavior of four serotypes of Salmonella and a cocktail of three E. coli strains on whole and sliced zucchini squash at 25+/-2 degrees C and 3 to 5 degrees C was tested. Squash fruit was collected in the markets of Pachuca city, Hidalgo State, Mexico. CB, TC, E. coli, and Salmonella were detected in 100, 70, 62, and 10% of the produce, respectively. The concentration ranged from 3.8 to 7.4 log CFU per sample for CB, and >3 to 1,100 most probable number per sample for TC and E. coli. On whole fruit stored at 25+/-2 degrees C or 3 to 5 degrees C, no growth was observed for any of the tested microorganisms or cocktails thereof. After 15 days at 25+/-2 degrees C, the tested Salmonella serotypes had decreased from an initial inoculum level of 7 log CFU to <1 log, and at 3 to 5 degrees C they decreased to approximately 2 log. Survival of E. coli was significantly greater than for the Salmonella strains at the same times and temperatures; after 15 days, at 25+/-2 degrees C E. coli cocktail strains had decreased to 3.4 log CFU per fruit and at 3 to 5 degrees C they decreased to 3.6 log CFU per fruit. Both the Salmonella serotypes and E. coli strains grew when inoculated onto sliced squash: after 24 h at 25+/-2 degrees C, both bacteria had grown to approximately 6.5 log CFU per slice. At 3 to 5 degrees C, the bacterial growth was inhibited. The squash may be an important factor contributing to the endemicity of Salmonella in Mexico.

Evaluación fisicoquímica, microbiológica y toxicológica de la degradación ambiental del río atoyac, México / Physicochemical, microbiological and toxicological evaluation of the environmental degradation of the atoyac river, Mexico / Avaliação fisicoquímica, microbiológica e toxicológica da degradação ambiental do rio atoyac, México

Desde 1995 se ha registrado un alto grado de deterioro en el río Atoyac, México, debido a los asentamientos humanos e industriales. El objetivo de este estudio fue evaluar la condición actual del río y establecer la relación entre los parámetros de la legislación vigente y las pruebas de toxicidad y mutagenicidad. Se determinaron parámetros de campo (color, olor, temperatura, CE, pH, OD), fisicoquímicos (SST, SDT, SSe, DBO5, DQO y GyA, Ntotal, Norg, Ptotal, Porg, ortofosfatos), metales pesados (As, Cd, Cu, Cr, Cr+6, Hg, Ni, Pb, Zn, Al, Fe, Mn), microbiológicos (coliformes fecales) con base en los límites máximos permisibles (LMP) en la NOM-001-ECOL-1996 y en los CE-CCA-001/89, análisis de toxicidad (Vibrio fischeri, Daphnia magna) y mutagenicidad (prueba de Ames con microsomas/Salmonella typhimurium), en época de sequía en nueve estaciones a lo largo de 85km. Los valores para OD, DBO5 y DQO fueron de 2-6, 11-270 y 22-1841mg·l-1, respectivamente. Los metales fueron detectados por debajo de los LMP en todas las estaciones, excepto en la estación 5 (0,002mg·l-1 de Hg) y la 8 (0,13mg·l-1 de Cr+6). Los coliformes fecales rebasaron los LMP en todas las estaciones. Los valores para Vibrio fischeri, Daphnia magna y se encuentran en 2-28 y 1-4UT, y para la prueba de Ames entre 5 y 63RM, indicando toxicidad y mutagenicidad desde la estación 3 a la 9. Se registró contaminación alta según la legislación vigente y un riesgo para la salud pública de acuerdo a los parámetros toxicológicos y mutagénicos.

A high degree of deterioration has been registered in the Atoyac river, Mexico, since 1995, due to local residences and industrial development. The aim of this study was to evaluate current environmental conditions at nine stations during the drought season along 85km of the river and to establish the relationship between current legislation parameters and toxicity and mutagenicity tests. Environmental quality was quantified using field observations (color, odor, temperature, CE, pH, and DO), physicochemical (SST, SDT, SSe, DBO5, DQO, GyA, Ntotal, Norg, Ptotal, Porg and orthophosphates), heavy metals (As, Cd, Cu, Cr, Cr+6, Hg, Ni, Pb, Zn, Al, Fe y Mn), microbiological (fecal coliforms) by comparison with the maximum permissible level (MPL) NOM-001-ECOL-1996 and CE-CCA-001/89, and toxicity (Vibrio fischeri, Daphnia magna) and mutagenicity (Salmonella/microsome, or Ames test) analysis. Values for DO, DBO5 and DQO were 2-6, 11-270 and 22-1841mg·l-1, respectively. Concentrations of heavy metals were below the MPL except at stations 5 (0.002mg·l-1 Hg) and 8 (0.13mg·l-1 Cr+6). Fecal coliform bacteria were above the MPL at all stations. Values for Vibrio fischeri, Daphnia magna and the Ames test were 2-28 UT, 1-4 UT and 5-63 RM, respectively, which indicated toxicity and mutagenicity from stations 3 to 9. The high level of contamination in this zone indicates that it is necessary to evaluate adherence to approved standards and to modify the existing regulations in order to include additional contamination parameters.

Desde 1995 tem sido registrado um alto grau de deterioração no rio Atoyac, México, devido aos assentamentos humanos e industriais. O objetivo deste estudo foi avaliar a condição atual do rio e estabelecer a relação entre os parâmetros da legislação vigente e as provas de toxicidade e mutagenicidade. Determinaram-se parâmetros de campo (cor, olor, temperatura, CE, pH, OD), fisicoquímicos (SST, SDT, SSe, DBO5, DQO e GyA, Ntotal, Norg, Ptotal, Porg, ortofosfatos), metais pesados (As, Cd, Cu, Cr, Cr+6, Hg, Ni, Pb, Zn, Al, Fe, Mn), microbiológicos (coliformes fecais) baseados nos limites máximos permissíveis (LMP) na NOM-001-ECOL-1996 e nos CE-CCA-001/89, análises de toxicidade (Vibrio fischeri, Daphnia magna) e mutagenicidade (prova de Ames com microssomas/Salmonella typhimurium), em época de seca em nove estações ao longo de 85km. Os valores para OD, DBO5 e DQO foram de 2-6, 11-270 e 22-1841mg·l-1, respectivamente. Os metais foram detectados por baixo dos LMP em todas as estações, exceto na estação 5 (0,002mg·l-1 de Hg) e a 8 (0,13mg·l-1 de Cr+6). Os coliformes fecais ultrapassaram os LMP em todas as estações. Os valores para Vibrio fischeri, Daphnia magna e se encontram em 2-28 e 1-4UT, e para a prova de Ames entre 5 e 63RM, indicando toxicidade e mutagenicidade desde a estação 3 a 9. Registrou-se contaminação alta segundo a legislação vigente e um risco para a saúde pública pelos parâmetros toxicológicos e mutagênicos.