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Longitudinal characterization of monophasic Salmonella Typhimurium throughout the pig’s life cycle
- Fernandes, Laura, Centeno, Maria Madalena, Couto, Natacha, Nunes, Telmo, Almeida, Virgílio, Alban, Lis, Pomba, Constança
- Veterinary microbiology 2016 v.192 pp. 231-237
- Salmonella Typhimurium, adulthood, adults, ampicillin, antibiotic resistance, ecosystems, farms, farrowing, feces, finishing, florfenicol, genotype-phenotype correlation, kanamycin, longitudinal studies, multiple drug resistance, neomycin, netilmicin, piglets, pulsed-field gel electrophoresis, sows, streptomycin, sulfonamides, swine production, tetracycline
- Swine have been described as an important reservoir of multidrug resistant monophasic Salmonella Typhimurium, though information on its ecology is scarce. A longitudinal study was performed in order to elucidate the Salmonella 4,,12:i:- dynamics throughout the pig’s production cycle. A total of 209 faecal samples were collected from 10 sows and in six sampling times during the life of 70 pigs from a Portuguese industrial farm, and 43 isolates of S. 4,,12:i:- were identified and characterized regarding clonality and antimicrobial resistance phenotype and genotype. Most isolates (n=42) exhibited resistance to at least ampicillin, kanamycin, neomycin, streptomycin, tetracycline and sulfonamides (encoded by blaTEM, aphAI-IAB, strA, strB, tetB and sul2, respectively). Isolates obtained during the finishing phase showed additional resistance to chloramphenicol and florfenicol (floR), gentamicin and netilmicin (aac(3′)-IV). To our knowledge, this study is the first description of aphAI-IAB in S. 4,,12:i:-. PFGE analysis showed uneven distribution of isolates into three clusters, A (n=34), B (n=8) and C (n=1). PFGE cluster A was predominant in sows (n=5) and piglets in the farrowing phase (n=17) and in pigs in the early finishing phase (n=11) suggesting a carryover from birth to adult age. The introduction of PFGE cluster B isolates in adulthood could have had an external source, reinforcing the relevance of environmental transmission in the farm ecosystem. This study reveals a dynamic interaction between monophasic S. Typhimurium and the pressures exerted under an intensive swine production setting.