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Listeria monocytogenes is a foodborne pathogen that causes listeriosis worldwide. In México, L. monocytogenes has been identified as a hazard of deli-meats. However, the genomic analysis that supports the transmission of L. monocytogenes strains via deli-meats and its role as a source for virulence and resistance genes is lacking. Here, we present four high-quality genome drafts of L. monocytogenes strains isolated from deli-meats in Mexico. In silico typing was used to determine the serotype, lineage, clonal complexes (CC), and multilocus sequence (ST). Also, comparative genomics were performed to explore the diversity, virulence, mobile elements, antimicrobial resistant and stress survival traits. The genome sequence size of these strains measured 3.05 ± 0.07 Mb with a mean value of 37.9%G+C. All strains belonged to linage I, which was divided into two groups: 4b, CC2, ST1 (n = 3) and 1/2b, CC5, ST5 (n = 1). The pangenome and core genome contained 3493 and 2625 genes, respectively. The strains harbor the L. monocytogenes pathogenicity island-1 (LIPI-1) and the same multidrug resistance pattern (fosX, norB, mprF, lin) via in silico analysis. Comparative analysis delineated the genomes as essentially syntenic, whose genomic differences were due to phage insertion. These results expand what is known about the biology of the L. monocytogenes strains isolated from deli-meats in Mexico and warns of the risk that these strains belong to epidemic linage and harbor virulence genes linked to human disease.

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Listeriosis is a foodborne disease caused by Listeria monocytogenes (Lm), which represents a public health problem. Lm has been identified as an important contaminating bacterium of ready-to-eat meat products (RTEM) in Mexico. The objective was to explore the risk factors for acquiring listeriosis due to sausage consumption by defining the consumer profile, evaluating the survival of Lm in sausage (5, 10, and 25 °C for 32 days) and performing a quantitative microbiological risk assessment. The survey of 100 participants revealed that the factors compromising the safety of the RTEM by the consumer are the extension of the shelf life. Acquiring packaged RTEM was observed as a safe habit. All respondents stated that they were unaware of listeriosis, but 18% reported infections linked to RTEM, mainly sausage. The sausage supports the growth of Lm, whose population increases in congruence with temperature (25 °C > 10 °C >5 °C) and storage time (P ≤ 0.05). The increase in temperature decreases the adaptation time (Lag25 °C = 1.0 h, Lag10 °C= 92.5 h, Lag5 °C = 226.1 h) and increases the growth rate (µ25 °C = 4.43 CFU/h, µ10 °C = 0.075 CFU/h, µ5 °C = 0.0026 CFU/h) of Lm on the sausage. The risk of listeriosis due to sausage consumption increased according to the increase in temperature: 5.53 × 10-8-1.42 × 10-5 (5 °C), 0.00616-0.111 (10 °C), and 0.109-1.00 (25 °C). Consumer education in the hygienic management of RTEM and information on associated pathogens will minimize the risk of disease.

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Salmonella enterica subsp. houtenae (IV) is a non-enteric subspecies of the genus Salmonella and has recently been implicated in extraintestinal diseases in humans. In Mexico, its reported that rivers are a reservoir of Salmonella houtenae, however, detailed information about the virulence and infective capacity of this bacterium are limited. Here, we present the high-quality genome draft of Salmonella houtenae str. CFSAN039533 isolated from a river in Culiacan, Mexico. In addition, its virulence, antimicrobial resistance profile and the use of carbon sources for its primary metabolism are analyzed. The genome sequence of CFSAN03953 strain comprises 4.74-Mb which contains 4266 protein coding genes and 77 tRNA genes. The strain belongs to the Marine serotype (48: g, z51: -), and showed several virulence genes related to the SPI-1, SPI-2, SPI-3, SPI-5 and fimbriae genes. The strain exhibited a susceptible phenotype, which contrasted with the resistance genes of aminoglycosides family identified into the genome. Carbon source degradation evaluation along with the genomic analysis, indicated that the strain can use a relatively broad spectrum of compounds related to the central metabolic pathways. This study provides information on the genetics and physiology of Salmonella houtenae that confirms its ability to survive and adapt to the environment. In addition, its pathogenic potential and infective capacity towards warm-blooded hosts are demonstrated.

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BACKGROUND: River water has been implicated as a source of non-typhoidal Salmonella (NTS) serovars in Mexico. OBJECTIVE: To dissect the molecular pathogenesis and defense strategies of seven NTS strains isolated from river water in Mexico. METHODS: The genome of Salmonella serovars Give, Pomona, Kedougou, Stanley, Oranienburg, Sandiego, and Muenchen were sequenced using the whole-genome shotgun methodology in the Illumina Miseq platform. The genoma annotation and evolutionary analyses were conducted in the RAST and FigTree servers, respectively. The MLST was performed using the SRST2 tool and the comparisons between strains were clustered and visualized using the Gview server. Experimental virulence assay was included to evaluate the pathogenic potential of strains. RESULTS: We report seven high-quality draft genomes, ranging from ~ 4.61 to ~ 5.12 Mb, with a median G + C value, coding DNA sequence, and protein values of 52.1%, 4697 bp, and 4,589 bp, respectively. The NTS serovars presented with an open pan-genome, offering novel genetic content. Each NTS serovar had an indistinguishable virulotype with a core genome (352 virulence genes) closely associated with Salmonella pathogenicity; 13 genes were characterized as serotype specific, which could explain differences in pathogenicity. All strains maintained highly conserved genetic content regarding the Salmonella pathogenicity islands (1-5) (86.9-100%), fimbriae (84.6%), and hypermutation (100%) genes. Adherence and invasion capacity were confirmed among NTS strains in Caco-2 cells. CONCLUSION: Our results demonstrated the arsenal of virulence and defense molecular factors harbored on NTS serovars and highlight that environmental NTS strains are waterborne pathogens worthy of attention.

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This study was performed to evaluate in vitro the adherence and invasiveness capacity of Salmonella Oranienburg and Saintpaul (isolated from river water) exposed to laboratory and river water growth conditions and inoculated into epithelial HEp-2 cell. Results showed that Salmonella Oranienburg and Salmonella Saintpaul showed lower ability to adhere and invade epithelial HEp-2 cells under both growth conditions as compared to Salmonella Typhimurium reference strain. S. Oranienburg adhesion capacity was not affected by the growth conditions, while S. Saintpaul exposed to river water significantly (p < 0.05) decreased its adhesion capacity by 75.7 %. On the contrary, S. Oranienburg exposed to river water reduced its invasion efficiency by 80 %, whereas S. Saintpaul showed no differences between growth conditions. In conclusion, this study suggests that the exposure to non-host conditions, such as river water, adversely affects the adhesion and invasiveness of Salmonella serotypes differently, impacting on their ability to re-enter a new host.

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Salmonella enterica subsp. enterica serovar Oranienburg is recognized as a foodborne pathogen widely distributed in the environment. Here, we report 18 draft genomes of S Oranienburg strains isolated from rivers in the northwestern region of Mexico.

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The microbiological quality of raw meat was evaluated in 18 retail units of the municipal market in Culiacan, Sinaloa. The levels of E. coli were measured using methods from the Bacteriological Analytical Manual, and the O157 sero-group and the H7 antigen were also evaluated using chromogenic media and PCR, respectively. The results were confirmed using real time-PCR (PCR-TR) and PCR to detect virulence genes (vt1, vt2, eaeA and hlyA). Of the samples tested, 31.5% were positive for E. coli, with concentrations between 100 and 700 CFU/g of beef. Nine suspected E. coli O157:H7 strains were isolated from 16 samples, which were then discarded by the PCR-TR test. The virulence genes were not detected. The microbial contamination of beef could indicate the presence of pathogens from fecal sources. To guarantee the quality of these products, it is important to incorporate food safety programs.

Se evaluó la calidad microbiológica de carne de res en 18 comercios del mercado municipal de Culiacán, Sinaloa. Para determinar E. coli se usó la metodología del Manual Bacteriológico Analítico, y para evaluar el serogrupo O157 y antígeno H7, se usaron medios cromogénicos y PCR, respectivamente. La confirmación se hizo por PCR tiempo real (PCR-TR) y la detección de genes de virulencia (vt1, vt, eaeA y hlyA), por PCR. El 31.5% de muestras resultaron positivas para E. coli, con concentraciones entre 100 y 700 UFC/g. Se aislaron nueve cepas presuntivas de E. coliO157:H7 de 16 muestras, las cuales fueron descartadas con la técnica PCR-TR. No se detectaron genes de virulencia. La contaminación microbiana de la carne de res podría indicar la presencia de patógenos provenientes de fuentes fecales. Por ello es importante incorporar programas de inocuidad para garantizar la calidad de estos productos.