Multidrug-resistant Escherichia coli and Salmonella spp. in pigs slaughtered for human consumption, a potential source for Humans?

Foodborne diseases are a serious public health problem worldwide. Food‐producing animals are considered a major source of these diseases through contamination of food-products, where pathogenic and drug-resistant Escherichia coli and Salmonella spp. are among the principal bacterial agents. Here, we aimed to assess the role of pig reservoir as potential transmission vehicle to Humans, contributing for the understanding of the epidemiology and population structure of these zoonotic agents in Portugal, since data is still limited.

Fecal samples were collected in different Portuguese slaughterhouses. After bacterial isolation in non- and selective media, serotyping of Salmonella and pathotyping of E. coli isolates were performed. Antimicrobial susceptibility was tested for a sub-set, by the disk diffusion method and interpreted according to EUCAST guidelines.

Overall, 124 stool samples were studied, mostly from Centro and Lisboa e Vale do Tejo Regions. While no Salmonella spp. was detected, E. coli was identified in all pig samples, with Shiga toxin-producing E. coli (STEC) detected in two samples. For a set of 50 E. coli isolates, preliminary antimicrobial resistance results showed that, with exception of one isolate, all were resistant to at least one of the 19 tested antibiotics (mostly erythromycin), where 17 of them displayed a multidrug-resistance profile (MDR). One of these MDR isolates was a STEC.

Although this study is still ongoing, our preliminary findings revealed the presence of MDR E. coli isolates in fecal samples of pigs slaughtered for human consumption, highlighting the role of this animal reservoir as potential source of these bacteria.