Serovars of Salmonella spp isolated from broiler chickens and commercial breeders in diverse regions in Brazil from July 1997 to December 2004

Dynamics of Salmonella enterica and antimicrobial resistance in the Brazilian poultry industry and global impacts on public health

Non-typhoidal Salmonella enterica is a common cause of diarrhoeal disease; in humans, consumption of contaminated poultry meat is believed to be a major source. Brazil is the world's largest exporter of chicken meat globally, and previous studies have indicated the introduction of Salmonella serovars through imported food products from Brazil. Here we provide an in-depth genomic characterisation and evolutionary analysis to investigate the most prevalent serovars and antimicrobial resistance (AMR) in Brazilian chickens and assess the impact to public health of products contaminated with S. enterica imported into the United Kingdom from Brazil. To do so, we examine 183 Salmonella genomes from chickens in Brazil and 357 genomes from humans, domestic poultry and imported Brazilian poultry products isolated in the United Kingdom. S. enterica serovars Heidelberg and Minnesota were the most prevalent serovars in Brazil and in meat products imported from Brazil into the UK. We extended our analysis to include 1,259 publicly available Salmonella Heidelberg and Salmonella Minnesota genomes for context. The Brazil genomes form clades distinct from global isolates, with temporal analysis suggesting emergence of these Salmonella Heidelberg and Salmonella Minnesota clades in the early 2000s, around the time of the 2003 introduction of the Enteritidis vaccine in Brazilian poultry. Analysis showed genomes within the Salmonella Heidelberg and Salmonella Minnesota clades shared resistance to sulphonamides, tetracyclines and beta-lactams conferred by sul2, tetA and blaCMY-2 genes, not widely observed in other co-circulating serovars despite similar selection pressures. The sul2 and tetA genes were concomitantly carried on IncC plasmids, whereas blaCMY-2 was either co-located with the sul2 and tetA genes on IncC plasmids or independently on IncI1 plasmids. Long-term surveillance data collected in the UK showed no increase in the incidence of Salmonella Heidelberg or Salmonella Minnesota in human cases of clinical disease in the UK following the increase of these two serovars in Brazilian poultry. In addition, almost all of the small number of UK-derived genomes which cluster with the Brazilian poultry-derived sequences could either be attributed to human cases with a recent history of foreign travel or were from imported Brazilian food products. These findings indicate that even should Salmonella from imported Brazilian poultry products reach UK consumers, they are very unlikely to be causing disease. No evidence of the Brazilian strains of Salmonella Heidelberg or Salmonella Minnesota were observed in UK domestic chickens. These findings suggest that introduction of the Salmonella Enteritidis vaccine, in addition to increasing antimicrobial use, could have resulted in replacement of salmonellae in Brazilian poultry flocks with serovars that are more drug resistant, but less associated with disease in humans in the UK. The plasmids conferring resistance to beta-lactams, sulphonamides and tetracyclines likely conferred a competitive advantage to the Salmonella Minnesota and Salmonella Heidelberg serovars in this setting of high antimicrobial use, but the apparent lack of transfer to other serovars present in the same setting suggests barriers to horizontal gene transfer that could be exploited in intervention strategies to reduce AMR. The insights obtained reinforce the importance of One Health genomic surveillance.

Occurrence, quantification, pulse types, and antimicrobial susceptibility of Salmonella sp. isolated from chicken meat in the state of Paraná, Brazil

The aim of this work was to verify the occurrence, quantification, pulse types, and antimicrobial susceptibility profiles of Salmonella sp. isolated from chicken meat produced and marketed in the state of Paraná, considered to be the state with the highest production of poultry meat in Brazil. Ninety-five of 300 (31.5%) frozen cuts of chicken were found to contain Salmonella sp., and 98 different isolates of Salmonella sp. were cultured from the positive samples. Quantification showed low Salmonella sp. loading, ranging from 0.12 to 6.4 MPN/g. The antimicrobial resistance test was performed against 16 agents from 6 different classes. All isolates were sensitive to meropenem, imipenem, chloramphenicol, and amikacin. The highest resistance rates were observed for nalidixic acid (95%), tetracycline (94%), doxycycline (94%), ampicillin (87%), amoxicillin with clavulanic acid (84%), ceftriaxone (79%), and ciprofloxacin (76%). A total of 84 (85.7%) of the isolates were identified with a multidrug resistant profile, 13 of which were found to have encoding genes extended-spectrum beta-lactamase (ESBL), especially blaCTX-M-2 e blaTEM-1. The major serovars identified were S. Typhimurium (43%) and S. Heidelberg (39%). The third most isolated serovar was S. Ndolo (6%), without previous reports of its presence in poultry meat in Brazil. Molecular characterization of S. Typhimurium and S. Heidelberg isolates by pulsed field gel electrophoresis (PFGE) showed a clonal relationship between all isolates of the same serovar (genetic similarity greater than 80%). Isolates of S. Typhimurium and S. Heidelberg with 100% similarity were found in up to five different geographic regions of the state, showing the potential for the spread of this pathogen in the Paraná poultry chain. Epidemiological surveys like this are important to understand the dynamics of dissemination and to monitor the prevalence of pathogens in the final products of poultry chains. In addition, to know the resistance profile of strains of Salmonella sp. present in food that contributes to the adoption of faster and more effective therapeutic measures, when necessary.

ISOLAMENTO DE SALMONELLA: COMPARAÇÃO DAS ETAPAS DE PRÉ- ENRIQUECIMENTO E ENRIQUECIMENTO DIRETO DE AMOSTRAS DE FEZES ARMAZENADAS POR 24 E 96 HORAS

RESUMO Este trabalho foi desenvolvido para avaliar comparativamente o isolamento de Salmonella sorotipos Enteritidis (SE) e Typhimurium (STM) a partir do enriquecimento direto (ED) ou processamento com pré-enriquecimento (PE) de amostras de fezes de aves adultas, armazenadas em água peptonada tamponada a 1% (APT) por 24 ou 96h a 4º C. Utilizou-se os caldos de enriquecimento Rapapport-Vassiliadis novobiocina (RVN), tetrationato-novobiocina (TN) e selenitonovobiocina (SN) e os meios para plaqueamento ágar verde brilhante (VB), ágar de MacConkey (MC), ágar de Hektoen (HE), ágar Salmonella-Shigella (SS), ágar xilose lisina desoxicolato (XLD) e ágar xilose lisina tergitol 4 (XLT4). O procedimento bacteriológico incluiu as etapas de pré-enriquecimento, enriquecimento em caldo seletivo, plaqueamento, testes bioquímicos presuntivos e confirmação sorológica com utilização de soros polivalentes anti-antígenos somáticos e anti-antígenos flagelares de Salmonella. Não houve diferença estatisticamente significativa (p > 0,05) para as amostras armazenadas por 24h submetidas tanto ao PE quanto ao ED. Entretanto, em armazenagem por 96h o número de isolamentos nas amostras submetidas ao PE foi estatisticamente superior às submetidas ao ED (p < 0,05). Quanto aos caldos enriquecedores, não houve diferença estatística de número de isolamentos (p > 0,05) entre os caldos SN e TN, mas o caldo RVN mostrou-se estatisticamente superior aos demais (p < 0,05). Para os meios de plaqueamento, o XLD destacou-se por promover maior número de recuperações, embora sem significado estatístico (p > 0,05) para as amostras estocadas por 24h. Entre os dois sorotipos de Salmonella (SE e STM) não houve diferença estatística no número de recuperações (p > 0,05).