This investigation provided an insight of the current status of AMR of Salmonella isolates in two States of Mexico and pinpoint the genes involved in AMR and their epidemiological relationship, the information could help to determine an adequate therapy in human and veterinary medicine.

Food-borne bacterial infections have worldwide importance, and a great variety of antibiotic resistance mechanisms, mainly of the chromosome type, have rapidly developed. Antimicrobial resistance was determined in this study in terms of the presence of extended-spectrum β-lactamases (ESBLs), plasmid AmpC β-lactamases (pAmpC), and plasmid-mediated quinolone resistance (PMQR) from 155 Escherichia coli isolates obtained from bovine carcasses from two states in Mexico (states of Mexico and Jalisco). Isolates were challenged with β-lactam antimicrobials (ampicillin, ceftazidime, and cefotaxime) and quinolones (nalidixic acid and ciprofloxacin). The presence of the bla TEM, bla SHV, bla CTX-M, bla OXA , bla CMY, bla MOX, bla LAT, bla BIL, qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA genes was examined by PCR. Clonal relationship was determined using pulsed-field gel electrophoresis (PFGE). The highest resistance was found to be to nalidixic acid (64 %), followed by ampicillin (32 %), ciprofloxacin (10 %), and ceftazidime and cefotaxime (both 1.3 %). bla CMY (n = 1), bla TEM (n = 24), qnrB (n = 9), and qnrS (n = 7) genes were detected. PFGE analysis showed that the majority of isolates had a different genotypic profile. To our knowledge, this is the first report of the presence of the qnrB, qnrS, and bla CMY genes in E. coli isolated from bovine meat in Mexico.

Salmonella is one of the major foodborne pathogens worldwide. The antimicrobial resistance (AMR) of this foodborne pathogen has raised a great concern in recent years. Studies on the frequency and characterization of Salmonella serotypes can help to improve our knowledge on the epidemiology of this pathogen. The purpose of this study was to compare the serotypes, AMR and genetic profiles of Salmonella isolates recovered from raw beef throughout the beef production chain and from human feces associated with clinical cases of salmonellosis. The serotype, AMR and pulsed-field gel electrophoresis profile of 243 Salmonella enterica isolates recovered from beef carcasses (n = 78), ground beef (n = 135), and human feces from clinical cases of salmonellosis (n = 30) were compared. Forty-three different Salmonella serotypes were identified and regardless of the source, the top five corresponded to Typhimurium, Give, Group B (partially serotyped), Infantis and Anatum. Twelve serotypes from beef carcasses were also found in ground beef, showing their presence throughout the beef production chain. Salmonella Typhimurium, Infantis, Anatum and Montevideo were the only serotypes identified in all sample types. Resistance to tetracyclines was the most frequent (41.2%) followed by resistance to aminoglycosides (37%), folate pathway inhibitors (21%), quinolones (20.2%), phenicols (17.1%), penicillins (15.6%) and cephems (7%). Multidrug resistance was observed in 28.8% of the isolates, and those from human feces showed resistance to a larger number of antimicrobials. Great concern arises from the resistance and reduced susceptibility observed to quinolones and cephalosporins because these drugs are the first line of treatment for invasive Salmonella infections. Twenty-seven distinct pulse-types were detected among 238 isolates. Clustering analysis for the most frequent serotypes identified groups of isolates with similar AMR profiles. Multidrug resistance spreading throughout the food production chain should be continually monitored and its importance emphasized.

Meat of bovine origin is one of the major vehicles in the transmission of verotoxigenic Escherichia coli (VTEC) to human consumers. This pathogen can produce serious human illness, including bloody diarrhea and hemolytic uremic syndrome. The aim of the current study was to characterize E. coli isolates (mainly VTEC strains) belonging to several serotypes in samples from cattle carcasses and feces of three municipal slaughter plants from Mexico State. The genetic diversity and molecular relatedness among the isolates was evaluated with multiple-locus variable-number tandem repeat analysis (MLVA). To our knowledge, and with the exception of E. coli O157:H7, this is the first time that serotypes analyzed here have been subtyped by MLVA in Mexico. MLVA typing grouped the 37 strains from this study into 30 distinct genotypes, 26 of which were unique. These findings indicate that cattle carcasses and feces from slaughter plants in Mexico are a source of VTEC that are genetically diverse in terms of serotypes and virulence profiles. The presence of these pathogens in carcasses indicates the high probability of the spread of VTEC strains during slaughter and processing.

Shiga toxin E. coli (STEC) is an important pathogen responsible for foodborne illness, this have been related with epidemic outbreaks in the past, mainly because of consumption of bovine meat. The objective of this study was identify the serotypes and Stx2 subtypes and associate them with their possible epidemiology. There were analyzed a total of 65 isolates from the collection of the Centro de Investigación y Estudios Avanzados en Salud Animal, Facultad de Medicina Veterinaria y Zootecnia of the Universidad Autónoma del Estado de México, from carcasses and feces of bovines at three different Municipal slaughterhouses. The identification of Stx2 gene by PCR at final point, sequencing and analyzed with the help of BLAST software. There were found O157:H7, O70:H16, O91:H10, O112ac:H2, O128ac:H26 serotypes, which have been reported to be present at infectious outbreaks previously by foodborne worldwide; 63.07% (41/65) of the Escherichia coli strains got amplified for Stx2 and after BLAS analysis it was confirmed its presence and a hypothetic protein. The presence of this serotypes in combination with different subtype’s, Stx2a, Stx2c, Stx2d, in carcasses and feces of bovine in must be considered as a potential risk for diseases an important problem of the public health.