Genomic diversity of Saccharomyces cerevisiae yeasts associated with alcoholic fermentation of bacanora produced by artisanal methods.

Bacanora is a spirituous beverage elaborated with Agave angustifolia Haw in an artisanal process. Natural fermentation is mostly performed with native yeasts and bacteria. In this study, 228 strains of yeast like Saccharomyces were isolated from the natural alcoholic fermentation on the production of bacanora. Restriction analysis of the amplified region ITS1-5.8S-ITS2 of the ribosomal DNA genes (RFLPr) were used to confirm the genus, and 182 strains were identified as Saccharomyces cerevisiae. These strains displayed high genomic variability in their chromosomes profiles by karyotyping. Electrophoretic profiles of the strains evaluated showed a large number of chromosomes the size of which ranged between 225 and 2200 kpb approximately.

Relationship of aquatic environmental factors with the abundance of Vibrio cholerae, Vibrio parahaemolyticus, Vibrio mimicus and Vibrio vulnificus in the coastal area of Guaymas, Sonora, Mexico.

Members of the genus Vibrio are common in aquatic environments. Among them are V. cholerae, V. vulnificus, V. parahaemolyticus and V. mimicus. Several studies have shown that environmental factors, such as temperature, salinity, and dissolved oxygen, are involved in their epidemiology. Therefore, the main objective of this study is to determine if there is a correlation between the presence/amount of V. cholerae, V, vulnificus, V. parahaemolyticus and V. mimicus and the environmental conditions of the seawater off the coast of Guaymas, México. Quantification of all four pathogenic bacteria was performed using the most probable number method, and suspected colonies were identified by polymerase chain reaction (PCR). Correlations were found using principal component analysis. V. parahaemolyticus was the most abundant and widely distributed bacteria, followed by V. vulnificus, V. mimicus and V. cholerae. Positive correlations between V. parahaemolyticus, V. vulnificus and V. mimicus with temperature, salinity, electric conductivity, and total dissolved solids were found. The abundance of V. cholerae was mainly affected by the sampling site and not by physicochemical parameters.

Fructose 6-phosphate phosphoketolase activity in wild-type strains of Lactobacillus, isolated from the intestinal tract of pigs.

Phosphoketolases are key enzymes of the phosphoketolase pathway of heterofermentative lactic acid bacteria, which include lactobacilli. In heterofermentative lactobacilli xylulose 5-phosphate phosphoketolase (X5PPK) is the main enzyme of the phosphoketolase pathway. However, activity of fructose 6-phosphate phosphoketolase (F6PPK) has always been considered absent in lactic acid bacteria. In this study, the F6PPK activity was detected in 24 porcine wild-type strains of Lactobacillus reuteri and Lactobacillus mucosae, but not in the Lactobacillus salivarius or in L. reuteri ATCC strains. The activity of F6PPK increased after treatment of the culture at low-pH and diminished after porcine bile-salts stress conditions in wild-type strains of L. reuteri. Colorimetric quantification at 505 nm allowed to differentiate between microbial strains with low activity and without the activity of F6PPK. Additionally, activity of F6PPK and the X5PPK gene expression levels were evaluated by real time PCR, under stress and nonstress conditions, in 3 L. reuteri strains. Although an exact correlation, between enzyme activity and gene expression was not obtained, it remains possible that the xpk gene codes for a phosphoketolase with dual substrate, at least in the analyzed strains of L. reuteri.

Protein-carbohydrate interactions between Lactobacillus salivarius and pig mucins.

Adherence to the gastrointestinal tract is a key element desirable for many of the proposed beneficial health effects of probiotic bacteria. The aims of this study were to determine the amounts of adhesion of 3 Lactobacillus salivarius strains (Lb6, Lb9, and Lb10) to porcine small intestinal mucins and to determine whether adhesion is a function of lectin-like activities. Dot and Western blot assays were performed to investigate bacterial adhesion. Several carbohydrates and glycoproteins were evaluated to determine whether they interfered with adhesion of the Lactobacillus strains to intestinal mucins and to determine whether they had lectin-like activities. The Lb9 and Lb10 strains had greater association with piglet mucins than did those from 22- to 24-wk-old finishing pigs (P = 0.021 and 0.037, respectively), whereas the Lb6 strain adhered to both (P = 0.138). Western blot assays showed that bacterial adhesion detected piglet mucosa from the duodenum, jejunum, and ileum. In finishing pigs, the adhesion was variable throughout the gastrointestinal tract. Galactose and mannose diminished the interaction of the Lb9 and Lb10 strains in intestinal mucosa (P = 0.028 and 0.026, respectively), whereas pig gastric mucin reduced the adhesion of the Lb6 strain (P = 0.013). Adhesion of the Lb9 and Lb10 strains to intestinal mucosa was less after protease treatment (P = 0.023 and 0.018, respectively), which indicates that proteins are needed for the Lb9 and Lb10 strains to recognize mucin. The Lb6 strain also demonstrated diminished adhesion after periodate treatment (P = 0.038). From these results, we suggest that the nature of the bacterial lectin-like substance is a surface protein that loosely binds to the bacterial cell surface. All the tested strains adhered to specific targets in the small intestinal mucosa of piglets, and the bacteria had lectin-like proteins involved in this adhesion.

Prevalence, types, and geographical distribution of Listeria monocytogenes from a survey of retail Queso Fresco and associated cheese processing plants and dairy farms in Sonora, Mexico.

In the first part of this study, samples were collected from farms, cheese processing plants (CPPs), and retail markets located in various geographical areas of Sonora, Mexico, over a 12-month period during the summer of 2004 and winter of 2005. Four (all Queso Fresco [QF] from retail markets) of 349 total samples tested positive for Listeria monocytogenes (Lm). Of these four positive samples, three were collected in the northern region and one in the southern region of Sonora. Additionally, two were collected during the winter months, and two were collected during the summer months. For the second part of the study, a total of 39 samples from a farm, a CPP, and retail markets were collected and processed according to a combination of the Norma Oficial Mexicana NOM-143-SSA1-1995.10 method (NOM) and the U.S. Food and Drug Administration (FDA) Bacteriological Analytical Manual method, and 27 samples from these same locations were collected and processed according to the U.S. Department of Agriculture Food Safety and Inspection Service method (USDA-FSIS). The NOM-FDA method recovered the pathogen from 6 (15%) of 39 samples (one cheese and five product contact surfaces), while the USDA-FSIS method recovered the pathogen from 5 (18.5%) of 27 samples (all product contact surfaces). In addition, the 40 isolates recovered from the 15 total samples that tested positive for Lm grouped into five distinct pulsotypes that were ca. 60% related, as determined by pulsed-field gel electrophoresis analysis. The results of this study confirmed a 3.4% prevalence of Lm in QF collected from retail markets located in Sonora and no appreciable difference in the effectiveness of either the NOM-FDA or USDA-FSIS method to recover the pathogen from cheese or environmental samples.

PCR identification of Salmonella: potential contamination sources from production and postharvest handling of cantaloupes.

Salmonella is one of the most frequently reported etiological agents in outbreaks of foodborne diseases associated with the consumption of cantaloupes. Sensitive and reliable methods for detecting and identifying foodborne microorganisms are needed. The PCR can be used to amplify specific DNA fragments and thus to detect and identify pathogenic bacteria. In this study, a PCR method was used to evaluate the incidence of Salmonella at cantaloupe production, harvest, and packaging steps, and the results were compared with those of the standard method for detection of Salmonella in foods (Mexican NOM-114-SSA1-1994). Salmonella was detected by both standard and PCR methods in 23.5% of the irrigation water samples but only by the PCR method in 9.1% of the groundwater samples, 4.8% of the chlorinated water samples, 16.7% of samples from the hands of packing workers, 20.6% of samples from the packed cantaloupes, and 25.7% of samples from the in-field cantaloupes. With the standard method, Salmonella was found in 8.3% of the crop soil samples. Statistical analysis indicated a significant difference in sensitivity (P < 0.05) between the two methods; the PCR method was 4.3 times more sensitive than the standard method. Salmonella was found at seven of the eight pointsevaluated during the production and postharvest handling of cantaloupe melons.