title: Longitudinal characterization of monophasic Salmonella Typhimurium throughout the pig's life cycle.
abstract: 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,[5],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,[5],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,[5],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.
authors.affiliation: Laboratory of Antimicrobial and Biocide Resistance, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Laura
authors.initials: L
authors.lastname: Fernandes
authors.affiliation: Laboratory of Antimicrobial and Biocide Resistance, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Maria Madalena
authors.initials: MM
authors.lastname: Centeno
authors.affiliation: Laboratory of Antimicrobial and Biocide Resistance, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Natacha
authors.initials: N
authors.lastname: Couto
authors.affiliation: Epidemiology Unit, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Telmo
authors.initials: T
authors.lastname: Nunes
authors.affiliation: Epidemiology Unit, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal.
authors.forename: Virgílio
authors.initials: V
authors.lastname: Almeida
authors.affiliation: Danish Agriculture & Food Council, Axelborg, Axeltorv 3DK-1609 Copenhagen V, Denmark.
authors.forename: Lis
authors.initials: L
authors.lastname: Alban
authors.affiliation: Laboratory of Antimicrobial and Biocide Resistance, CIISA, Faculdade de Medicina Veterinária, Universidade de Lisboa (FMV-UL), Av. da Universidade Técnica, 1300-477 Lisbon, Portugal. Electronic address: cpomba@fmv.ulisboa.pt.
authors.forename: Constança
authors.initials: C
authors.lastname: Pomba
mesh_terms: D000375:Aging; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents
keywords: Antimicrobial resistance; Longitudinal study; Monophasic Salmonella Typhimurium; PFGE; Swine