Abstract
Pigs are important reservoirs of Shiga toxin-producing Escherichia coli (STEC). The entrance of these strains into the food chain implies a risk to consumers because of the severity of hemolytic uremic syndrome. This study reports the prevalence and characterization of STEC throughout the pork production chain. From 764 samples, 31 (4.05%) were stx positive by PCR screening. At farms, 2.86% of samples were stx positive; at slaughter, 4.08% of carcasses were stx positive and at boning rooms, 6% of samples were stx positive. These percentages decreased in pork meat ready for sale at sales markets (4.59%). From positive samples, 50 isolates could be characterized. At farms 37.5% of the isolates carried stx1/stx2 genes, 37.5% possessed stx2e and 25%, carried only stx2. At slaughter we detected 50% of isolates positive for stx2, 33% for stx2e, and 16% for stx1/stx2. At boning rooms 59% of the isolates carried stx1/stx2, 14% stx2e, and 5% stx1/stx2/stx2e. At retail markets 66% of isolates were positive for stx2, 17% stx2e, and 17% stx1/stx2. For the other virulence factors, ehxA and saa were not detected and eae gene was detected in 12% of the isolates. Concerning putative adhesins, agn43 was detected in 72%, ehaA in 26%, aida in 8%, and iha in 6% of isolates. The strains were typed into 14 E. coli O groups (O1, O2, O8, O15, O20, O35, O69, O78, O91, O121, O138, O142, O157, O180) and 10 H groups (H9, H10, H16, H21, H26, H29, H30, H32, H45, H46). This study reports the prevalence and characterization of STEC strains through the chain pork suggesting the vertical transmission. STEC contamination originates in the farms and is transferred from pigs to carcasses in the slaughter process and increase in meat pork at boning rooms and sales markets. These results highlight the need to implement an integrated STEC control system based on good management practices on the farm and critical control point systems in the food chain.
Highlights
Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens that can cause severe disease, including a life-threatening complication such as bloody diarrhea and hemolytic uremic syndrome (HUS; Paton and Paton, 1998)
AIDA was identified in diffusely adhering diarrheagenic E. coli strain and is associated with edema disease and diarrhea in pigs (Niewerth et al, 2001), contributing to bacterial intercellular aggregation and biofilm formation (Restieri et al, 2007); iha encode for an outer membrane protein identified as a bacterial adherence conferring iron regulated gene (Tarr et al, 2000) and Agn43 and EhaA are autotransporter proteins of O157:H7 involved in adhesion and biofilm formation (Wells et al, 2008)
The results indicate that STEC occurrence is widespread throughout pork production chain
Summary
Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens that can cause severe disease, including a life-threatening complication such as bloody diarrhea and hemolytic uremic syndrome (HUS; Paton and Paton, 1998). HUS is one of the most common etiologies for acute kidney injury and an important cause of acquired chronic kidney disease in children (Grisaru, 2014) This damage is produced by the action of cytotoxins Stx and Stx, being Stx and their subtypes associated more frequently with HUS (Beutin et al, 2007). AIDA was identified in diffusely adhering diarrheagenic E. coli strain and is associated with edema disease and diarrhea in pigs (Niewerth et al, 2001), contributing to bacterial intercellular aggregation and biofilm formation (Restieri et al, 2007); iha encode for an outer membrane protein identified as a bacterial adherence conferring iron regulated gene (Tarr et al, 2000) and Agn and EhaA are autotransporter proteins of O157:H7 involved in adhesion and biofilm formation (Wells et al, 2008). Other factors are involved in human pathogenicity such as a plasmid that encoded enterohemolysin (EhxA), among others (Feng and Reddy, 2013)
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