Zoonotic bacteria in the food chain: antimicrobial resistance and associated factors in Portugal
Abstract Antimicrobial resistance (AMR) poses a threat to public health and animal food-production plays a crucial role in AMR spread. We thus aimed to characterize AMR profiles and associated factors in zoonotic bacterial isolates in Portugal. Data from the Portuguese AMR surveillance program on animal populations and derived food, 2014-2018, was used. AMR frequency was described in E coli, Campylobacter and Salmonella isolates from poultry and pigs, according to antibiotic and samples tested. For Salmonella, AMR associated factors were studied: animal populations (broilers, laying hens, pigs) and derived meat, sampling stage (farm, slaughterhouse, processing plant), sample type (environmental, carcase, food), sampler (HACCP, industry, official, official and industry), sample context (control and eradication programmes, monitoring), year (2014-2018) and season. Logistic regression was applied to estimate crude (OR) and adjusted odds ratio (aOR) with 95% confidence intervals (95%CI). The final model was obtained using a backward stepwise method. We assessed 2157 E Coli, 561 Campylobacter and 826 Salmonella isolates. AMR rates were higher to cefepime (91-98%) in E coli in all sample types; cefotaxime (100%) in E coli in broiler's meat; nalidixic acid (79-96%) in E coli and Campylobacter in poultry and derived meat; ciprofloxacin (50-98%) in all bacteria isolates from poultry and derived meat. For Salmonella, AMR was more likely in pig's meat (OR 3.66; 95%CI:1.19-2.82), slaughterhouses (OR 10.18; 95%CI:4.69-26.70), carcases (OR 5.90;95%CI:3.74-9.69). The final model indicated a lesser chance of AMR in laying hens (aOR .21; 95%CI:.11-.37), industry sampling (aOR .25; 95%CI:.07-.73), 2018 (aOR .24; 95%CI:.13-.42), and a higher chance in summer (aOR 2.39; 95%CI:1.34-4.28). The findings support the need for control measures on the use of key antibiotics in veterinary medicine. AMR occurrence in Portugal seems to be related to summer, although less in laying hens and in 2018. Key messages AMR in bacterial isolates suggests the need for integrated actions to mitigate and control the use of 3rd and 4rd generation cephalosporins, fluoroquinolones and quinolones in animal production. AMR occurrence in Portugal seems to be further related to summer conditions, while comparing to other seasons.