Exploring the food production chain as a source of bacteria resistant to last-resort antibiotics

• Autor(a) principal: Cabral, Laura Mariana Gouveia
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/139502
• topic: Antibiotics; Enterobacteriaceae; Resistant; Slaughterhouse; Staphylococci; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Antibiotic-resistant bacteria spread through the food chain is a public health problem. However, the role of the meat production chain in antibiotic resistance dissemination is still unknown. Of concern is the emergence of resistance to antibiotics that are the last resort for human infection treatment. Samples collected along the pig processing chain in 2016, from live pigs to slaughterhouse operators, were screened for Gram-negative bacteria and staphylococci resistant to linezolid, tigecycline and colistin. Gram-negative bacteria resistant to last-resort antibiotics and representative staphylococci were identified by 16S rRNA/ tuf sequencing and susceptibility to other antibiotics was also evaluated. The whole genome was sequenced, and bioinformatics tools were used to determine the content in antimicrobial resistance genes and characterize the bacterial genetic background. Cross-transmission along the pig production chain was evaluated by single nucleotide polymorphisms (SNPs) analysis. Overall, 34% of Gram-negative isolates were tigecycline resistant and 13% were colistin-resistant, being mainly from the operators and live pigs. Genes oqxA/oqxB, encoding multidrug efflux pumps, were carried by 71% of tigecycline-resistant Enterobacteriaceae, but colistin-resistant determinants were not found. Resistance to these last-resort antibiotics was probably associated with the overexpression of the efflux pumps (tigecycline) and mutations in genes involved in lipid A biosynthesis (colistin). We detected no resistance to last-resort antibiotics among staphylococci, but resistance to beta-lactams, tetracyclines and macrolides was frequent. Although we did not identify transmission of Gram-negative bacteria resistant to last-resort antibiotics, closely related S. hyicus were found in equipment, operators, and pigs. Results suggest that slaughterhouses are reservoirs for multidrug-resistant bacteria, including those resistant to last-resort antibiotics and confirmed the occurrence of bacterial transmission between different sampling sites. The fact that high rates of resistance to last-resort antibiotics were detected, highlights the importance and urgency of taking action on both surveillance and control of these bacteria in the veterinary setting.