Hydrophobic and adhesive patterns of lactic acid bacteria and their antagonism against foodborne pathogens on tomato surface (Solanum lycopersicum L.).

AIMS: To evaluate tomato epiphyte lactic acid bacteria (LAB) hydrophobicity and auto-aggregation as an indicator of bacteria adhesion to tomato. Likewise, use LAB adhesion and co-aggregation as mechanisms to antagonize pathogen attachment. METHODS AND RESULTS: Fifty-four LAB were screened to evaluate their hydrophobic, auto- and co-aggregative properties against Salmonella Typhimurium, Saintpaul, Montevideo and Escherichia coli O157:H7. Subsequently, tomato adhesion of Enterococcus faecium Col1-1C, Weisella cibaria 11-E-2 and W. confusa Col 1-13 with high, medium and low hydrophobicity and high co-aggregation was investigated as well as their pathogen antagonism. Results indicate that bacteria hydrophobicity and auto-aggregation correspond to LAB adhesion to tomato. Enterococcus faecium Col1-1C interfered in most of the pathogen adhesion and micrographs revealed that such effect could be related to the inhibition of structures-type biofilm on E. coli O157:H7 and the aggregate formation on Salmonella. CONCLUSIONS: Lactic acid bacteria hydrophobicity and auto-aggregation can estimate bacteria adhesion to tomato and adhesive and co-aggregative properties could serve as a tool to antagonize foodborne pathogens under specific conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This study evidence the interference of Ent. faecium Col1-1C in E. coli O157:H7 biofilm formation and Salmonella colonization.

Utilization of by-products of Hibiscus sabdariffa L. as alternative sources for the extraction of high-quality pectin.

The by-products of Hibiscus sabdariffa L. (HsL), obtained after soaking or decoction of the calyces of Colima and Sudan cultivars, were used for pectin extraction. After soaking, the wastes of both cultivars gave higher yields of pectin than those obtained by decoction. The pectin of the wastes by soaking presented high methoxyl groups, galacturonic acid content, viscosity and gelling capacity. Pectin of this treatment also exhibited bands in the regions of 1750 cm-1 and 1630 cm-1 that represents the C=O stretching vibrations of methyl ester and the amounts and degree of esterification of the HsL pectin. Interestingly, the pectin retained the typical red color of fresh HsL calyces. The amounts of anthocyanins and ascorbic acid of pectin did not show effects against pathogenic microorganisms. Nonetheless, pectin of the Sudan HsL wastes obtained by soaking, exhibited higher properties than those of the citric pectin, thus, demonstrating its potential for industrial applications.

Microbiological safety of domestic refrigerators and the dishcloths used to clean them in Guadalajara, Jalisco, Mexico.

Household refrigerators are a potential pathogen contamination source for foods. An evaluation of the microbiological safety of 200 refrigerators in Guadalajara, Jalisco, Mexico, was made by visual inspection, ATP-bioluminescence levels, indicator microorganisms including Escherichia coli and Staphylococcus aureus, and the presence of Listeria monocytogenes and Salmonella. Additionally, interviews of the owners of the refrigerators were carried out to determine relationships between food storage practices, demographic aspects, and microbiological status. Dishcloths used to clean refrigerators were also analyzed. Operational conditions (cleanliness, fullness, organization, frequency of cleaning, and temperature) were evaluated by trained observers. Results showed deficient cleanliness in 55% of refrigerators, 22% were completely full, 43% very disorganized, 28% were usually cleaned only once in 3 to 6 months, and 53% had internal temperatures >7.1°C. ATP-bioluminescence levels were >300 relative light units on 67 and 74% of shelves and drawers, respectively, indicating that surfaces were dirty according to the luminometer manufacturer. Psychrotrophic aerobic bacteria counts on shelves, drawers, and dishcloths were 6.3, 5.2, and 6.3 log CFU/cm(2); for coliform bacteria, 5.2, 3.9, and 4.7 CFU/cm(2); for E. coli, 3.7, 3.5, and 4.8 CFU/cm(2); and for Staphylococcus aureus, 2.1, 2.5, and 2.3 CFU/cm(2), respectively. L. monocytogenes and Salmonella were isolated from 59.5, 20.5, and 17% and 32.5, 8.0 and 12.5% of shelves, drawers, and dishcloths, respectively. Four Salmonella serotypes and nine serogroups (partially serotyped isolates) were identified. The most prevalent were Salmonella Anatum (39.5%), Salmonella group E1 (19.7%), and Salmonella group E1 monophasic (12.5%). Operational conditions and microbiological status were clearly deficient in sampled refrigerators, highlighting the consequent risk of foodborne disease among users. Educational programs are needed to improve the domestic food safety in Mexico.

Lactobacillus fermentum BCS87 expresses mucus- and mucin-binding proteins on the cell surface.

AIMS: To identify and characterize adhesion-associated proteins in the potential probiotic Lactobacillus fermentum BCS87. METHODS AND RESULTS: Protein suspensions obtained from the treatment of Lact. fermentum BCS87 with 1 mol 1(-1) LiCl were analysed by Western blotting using HRP-labelled porcine mucus and mucin. Two adhesion-associated proteins with relative molecular weight of 29 and 32 kDa were identified. The N-terminal and internal peptides of the 32 kDa protein (32-Mmubp) were sequenced, and the corresponding gene (32-mmub) was found by inverse polymerase chain reaction. The complete nucleotide sequence of 32-mmub revealed an open reading frame of 903 bp encoding a primary protein of 300 amino acids and a mature protein of 272 residues. A basic local alignment search showed 47-99% identity to solute-binding components of ATP binding cassette transporter proteins in Lactobacillus, Streptococcus and Clostridium. An OpuAC-conserved domain was identified and phylogenetic relationship analysis confirmed that 32-Mmubp belongs to the OpuAC family. CONCLUSIONS: Adhesion of Lact. fermentum BCS87 appeared to be mediated by two surface-associated proteins. 32-Mmubp is a component of ABC transporter system that also functions as an adhesin. SIGNIFICANCE AND IMPACT OF THE STUDY: Characterization of 32-Mmubp and 32-mmub will contribute to understanding the host-bacteria interactions of Lact. fermentum with the intestinal tract of pigs.