Bacillus cereus can cause diarrhea and emetic syndromes after ingestion of food contaminated with it. This ability is due to the production of enterotoxins by this microorganism, these being the hemolysin BL complex, which is involved in the diarrheal syndrome, and cereulide, which is responsible for the emetic syndrome. The detection of genes associated with the production of these toxins can predict the virulence of strains isolated from contaminated food. In this paper, we analyzed 100 samples of vegetables, 25 of each kind (broccoli, coriander, carrot, and lettuce) obtained from different markets in Mexico City and its metropolitan area. B. cereus was isolated in 32, 44, 84, and 68% of the samples of broccoli, carrot, lettuce, and coriander, respectively. The hblA gene (encoding one of the three subunits of hemolysin BL) was amplified in 100% of the B. cereus isolates, and the ces gene (encoding the cereulide) could not be amplified from any of them. This is the first report of B. cereus isolation from the vegetables analyzed in this work and, also, the first report in Mexico of the isolation from vegetables of strains with potential virulence. The results should serve as evidence of the potential risk of consuming these foods without proper treatment.

Honey is a product used as a natural sweetener and in several regions of Mexico and other countries it is also used as a therapeutic agent. Microbiological contamination of honey can occur during its extraction and handling. Due to the use and consumption of honey we highlighted here the importance of the assessment of its microbiological quality. One thousand nine hundred twenty samples obtained from 8 honey-producing states from Mexico were analyzed. From these samples, 40.5% (777/1920) did not comply with the NMX-036-NORMEX-2006 specification. Forty five percent (777/1920) of the samples did not comply with the mesophilic aerobic microorganism specification, neither did 17% (327/1920) of the samples with the specification for molds and 18.1% (348/1920) with the specification for yeasts. With regard to coliform bacteria, the samples contained less than 3 NMP/g. Two percent of the samples contained lactic acid bacteria (LAB), Clostridium perfringens was observed in amounts of more than 100CFU/g. None of the samples from the different states contained more than 100CFU/g of Staphylococcus aureus; Salmonella spp. was absent in all samples. It is important to avoid contamination sources and implement good hygienic practices in order to maintain and improve the quality of Mexican honeys since a large percentage of them are intended for export. If these honeys are intended for therapeutic use, it is necessary to ensure that they comply with all quality parameters and to apply specific treatments that guarantee the removal of any pathogen that may represent a risk to the patients's health.

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No reports on the incidence of Clostridium perfringens in popularly-consumed food from Mexico City have been published; neither are there any reports that have analyzed food consumed in popular markets and less established restaurants. Therefore, this study is aimed at providing data to evaluate the relevance of C. perfringens as an etiologic agent of food-borne diseases. Of the 650 analyzed samples, 106 (16.3%) were positive for C. perfringens; 6.4% (16/250) isolates were from barbacoa, 19% (38/200) from head, and 13% (52/200) from gut tacos. The presence of C. perfringens in these popular-consumed foods demonstrates its relevance as an etiologic agent of food-borne diseases, and confirms the great sanitary risk involved in their consumption. These results may serve as a basis for the Mexican sanitary authorities to control the microbiological quality of street-made foods.