First isolation of the enterohaemorrhagic Escherichia coli O145:H- from cattle in feedlot in Argentina

BACKGROUND: Enterohaemorrhagic Escherichia coli (EHEC) is considered to be common cause of haemorrhagic colitis (HC), thrombotic thrombocytopenic purpura and haemolytic uraemic syndrome (HUS) in humans. In a previous paper, we have demonstrated that EHEC are commonly found in the intestines of livestock. Infections in humans are, in part, a consequence of consumption of undercooked meat or raw milk. Argentina has one of the highest records of HUS (300–400 cases/year; 22/100,000 children under 4 years of age). The aim of this work is to communicate the first isolation of O145:H-from cattle in this country and characterize the virulence cassette, providing useful information to evaluate the risk of foodborne transmission of this emergent non-O157:H7 serotype. RESULTS: EHEC O145:H- was isolated from cattle in an Argentinian feedlot. Pheno- and genotype of nine strains were characterized, corresponding to several virulence cassettes: VT2(+)eaeA(+) Mp(+) (n = 5), VT2(+)eaeA(+) (n = 1), VT1(+)eaeA(+) Mp(+) (n = 2), and VT1(+)eaeA(+) (n = 1). Strains isolated from the same animal were considered only when they showed a different virulence pattern. The clonal relationship was studied by RAPD. Strains were distributed in two RAPD profiles, which corresponded to the presence of either, VT1(+) or VT2(+) genotype. No difference was detected by RAPD analysis between Mp(+) or Mp(-) strains. CONCLUSIONS: This was the first isolation of EHEC O145:H- serotype in Argentina enlarging the list of non-O157:H7 serotypes isolated from cattle in this country by us. All O145:H-strains carried several virulence factors which allow us to predict their potential ability to develop haemolytic uraemic syndrome in humans

Shiga toxin-producing <i>Escherichia coli</i> in beef retail markets from Argentina

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause mild or serious diseases and can lead to people death. This study reports the prevalence and characteristics of STEC O157 and non-O157 in commercial ground beef and environmental samples, including meat table, knife, meat mincing machine, and manipulator hands (n = 450) obtained from 90 retail markets over a nine-month period. The STEC isolates were serotyped and virulence genes as stx (Shiga toxin), rfbO157] (O157 lipopolysaccharide), fliCH7 (H7 flagellin), eae (intimin), ehxA (enterohemolysin) and saa (STEC autoagglutinating adhesin), were determined. STEC O157 were identified in 23 (25.5%) beef samples and 16 (4.4%) environmental samples, while STEC non-O157 were present in 47 (52.2%) and 182 (50.5%), respectively. Among 54 strains isolated, 17 were STEC O157:H7 and 37 were STEC non-O157. The prevalent genotype for O157 was stx2/eae/ehxA/fliCH7 (83.4%), and for STEC non-O157 the most frequent ones were stx1/stx2/saa/ehxA (29.7%); stx2 (29.7%); and stx2/saa/ehxA (27%). None of the STEC non-O157 strains were eae-positive. Besides O157:H7, other 20 different serotypes were identified, being O8:H19, O178:H19, and O174:H28 the prevalent. Strains belonging to the same serotype could be isolated from different sources of the same retail market. Also, the same serotype could be detected in different stores. In conclusion, screening techniques are increasingly sensitive, but the isolation of STEC non-O157 is still a challenge. Moreover, with the results obtained from the present work, although more studies are needed, cross-contamination between meat and the environment could be suspected.Instituto de Genética Veterinari

Shiga toxin-producing <i>Escherichia coli</i> in beef retail markets from Argentina

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens that cause mild or serious diseases and can lead to people death. This study reports the prevalence and characteristics of STEC O157 and non-O157 in commercial ground beef and environmental samples, including meat table, knife, meat mincing machine, and manipulator hands (n = 450) obtained from 90 retail markets over a nine-month period. The STEC isolates were serotyped and virulence genes as stx (Shiga toxin), rfbO157] (O157 lipopolysaccharide), fliCH7 (H7 flagellin), eae (intimin), ehxA (enterohemolysin) and saa (STEC autoagglutinating adhesin), were determined. STEC O157 were identified in 23 (25.5%) beef samples and 16 (4.4%) environmental samples, while STEC non-O157 were present in 47 (52.2%) and 182 (50.5%), respectively. Among 54 strains isolated, 17 were STEC O157:H7 and 37 were STEC non-O157. The prevalent genotype for O157 was stx2/eae/ehxA/fliCH7 (83.4%), and for STEC non-O157 the most frequent ones were stx1/stx2/saa/ehxA (29.7%); stx2 (29.7%); and stx2/saa/ehxA (27%). None of the STEC non-O157 strains were eae-positive. Besides O157:H7, other 20 different serotypes were identified, being O8:H19, O178:H19, and O174:H28 the prevalent. Strains belonging to the same serotype could be isolated from different sources of the same retail market. Also, the same serotype could be detected in different stores. In conclusion, screening techniques are increasingly sensitive, but the isolation of STEC non-O157 is still a challenge. Moreover, with the results obtained from the present work, although more studies are needed, cross-contamination between meat and the environment could be suspected.Instituto de Genética Veterinari

Detection and Characterization of Salmonella Serotypes in the Production Chain of Two Pig Farms in Buenos Aires Province, Argentina

The aim of the present study was to determine the prevalence of Salmonella in the pork production chain and to characterize Salmonella isolates. From 764 samples, 35 (4.6%) were positive for Salmonella spp., as determined by biochemical tests and the presence of the invA gene. From these, 2.6, 2.0, 8.8, and 8.0% corresponded to samples collected from farms, slaughterhouses, boning rooms and retail markets, respectively. Salmonella strains were classified into five serotypes and distributed as follows: S. Typhimurium in the pork production chain, S. Kentucky in farms and slaughterhouses, S. Brandenburg in slaughterhouses, S. Livingstone in farms and S. Agona in boning rooms and retail markets. Interestingly, the antimicrobial susceptibility testing indicated that all 35 Salmonella spp.-positive isolates were resistant to at least one antimicrobial agent, and 30 were multidrug-resistant (MDR) and resistant to different classes of antibiotics. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) analysis showed clonal relatedness among strains isolated from farms, boning rooms and retail markets. The presence of antibiotic-resistant Salmonella in food poses a potential health hazard to consumers

Expression of hes, iha, and tpsA codified in locus of adhesion and autoaggregation and their involvement in the capability of shiga toxin-producing Escherichia coli strains to adhere to epithelial cells

Abstract Objectives Shiga toxin-producing Escherichia coli strains LAA-positive are important cause of human infection. The capability to adhere to epithelial cells is a key virulence trait, and genes codified in LAA pathogenicity island could be involved in the adhesion during the pathogenesis of LAA-positive STEC strains. Thus, our objectives were to compare hes-negative and hes-positive STEC strains in their adherence capability to epithelial cells (HEp-2) and to evaluate the expression levels of the hes, iha, and tpsA in the bacteria adhered and non-adhered to HEp-2 cells. These genes are encoded in LAA, and are virulence factors that participate in adhesion and autoaggregation. Results We could not observe differences between the adhesion of strains but also in the expression level of of hes, iha, and tpsA. Genes encoded in LAA contribute to the adhesion phenotype though the expression of STEC adhesins is a coordinated event that depends not only the strain but also on the environment as well as its genetic background. Therefore, the results of this study suggest that LAA ,the most prevalent PAI among LEE-negative STEC strains, plays a role in pathogenesis