Presence of Aeromonas spp in water from drinking-water- and wastewater-treatment plants in Mexico City.

The frequency of Aeromonas spp in three wastewater-treatment plants (WWTPs) and two drinking-water plants (DWPs) in México City was determined. Samples were taken throughout a year by the Moore's swab technique. A total of 144 samples were obtained from WWTPs and 96 from DWPs of both incoming and outflowing water. Aeromonas spp was isolated in 31% of the samples, from both kinds of sources. The technique used for the isolation of the pathogen was suitable for samples with high associate microbiota content and for those with a scarce microbial content. The presence of mesophilic-aerobic, coliform, and fecal-coliform organisms was investigated to determine whether there was any correlation with the presence of Aeromonas spp. Most samples from WWTP, which did not comply with the Mexican standards, had the pathogen, and some of the samples from the outflow of the DWP, which were within the limits set by the Mexican standards, also had Aeromonas spp. Most samples containing Aeromonas spp. had concentrations below 0.1 ppm residual chlorine, and the strains were resistant to 0.3 ppm, which supports the recommendation to increase the residual chlorine concentration to 0.5 to 1.0 ppm, as recommended by the Mexican standards.

Survival of Brucella abortus in milk fermented with a yoghurt starter culture.

In countries such as Mexico, brucellosis is still an important public health problem due to the consumption of non-pasteurized milk and dairy products, contaminated with Brucella spp. The aim of this study was to look into the survival of Brucella abortus during fermentation of milk with a yoghurt starter culture and storage at refrigeration temperature. Sterile skim milk was inoculated with B. abortus at two concentrations, 10(5) and 10(8) CFU/ml simultaneously with a yoghurt starter culture of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii subspecie bulgaricus). Inoculated flasks were incubated at 42 degrees C, followed by refrigeration at 4 degrees C. Samples were taken during fermentation and during storage and viable count of B. abortus and lactic acid bacteria and pH were determined. Results showed that after 10 days of storage at 4 degrees C, B. abortus was recovered in fermented milk at a level of 10(5) CFU/ml, despite the low pH below 4.0. Therefore B. abortus is able to survive in fermented milk. This finding may imply that non-pasteurized fermented milk contaminated with Brucella abortus could be a means of transmission of these bacteria.

Ausencia de vibrio parahaemolyticus en pescado crudo / Abscence of vibrio parahemolyticus in raw fish

Se analizaron 389 muestras de pescado colectadas por los Promotores de la Secretaria de Salud a lo largo de un año. Se analizaron 329 muestrs de pescado por la técnica de Nava y 60 muestras por la técnica de la FDA; no se obtuvieron aislamientos positivos de Bibrio parahaemolyticus aún en la época de verano en la cual se tiene la mayor incidencia del microorganismo de acuerdo a datos bibliográficos. Se señala que aunque el microorganismo pudo estar presente en los pescados analizados, debido al tamaño de la muestra analizada y al manejo inadecuado de los pescados desde la pesca hasta su venta se propicia un incremento de la flora asociada lo que dificulta el aislamiento de Vibrio parahaemolyticus por las técnicas utilizadas