Abstract
Background. Antibiotic resistant (ABR) Salmonella clones and the contributions of diverse environmental stressors (e.g. metals) widely used in food animal production (feed/disinfectants/antiseptics) for their selection/persistence are a current public health concern. We aimed to characterize metal tolerance and its associated genetic elements in clinical relevant ABR Salmonella clonal lineages. Methods. Portuguese Salmonella non-typhoid isolates (n=121/2000-2011) from human/non-human sources belonging to 16 serotypes were selected. The isolates included the 2 most frequent serotypes, S.Enteritidis (n=4) and S.Typhimurium (n=12), and the emergent S.4,[5],12:i:- (n=64) and S.Rissen (n=26). They are representative of different PFGE and Sequence Types (ST) and associated with particular ABR phenotypes/genotypes. Genes associated with ABR/integrons (Int), Cu R (pcoD), Ag/Cu R (silA- silE), HgR (merA), As R (arsB) or TeR (terF) were searched by PCR/sequencing. MICs to CuSO 4 and AgNO3 were determined in aerobic/anaerobic atmospheres by agar dilution method and susceptibility to 10 antibiotics by disk diffusion methods. Conjugation assays, genomic location (I-CeuI/S1-PFGE/hybridization) and plasmid (PL) analysis (PBRT/sequencing) were done. Results. Metal tolerance genes silA-silE (69%), pcoD (51%), merA (50%), terF (2%) or arsB (1%) were found in different serotypes/clones. S.Rissen (ST469; 62%-blaTEM-aadA2- sul1/sul3-tetA-dfrA12) carried pcoD+silA-silE in chromosome (Ch) as S.4,[5],12:i:- from European clone (n=22/ST34), which also have co-located ABR genes (blaTEM-strA-strB-sul2- tetB) and the majority merA. In contrast, S.Typhimurium monophasic variant of the Spanish (n=5/ST19) and Portuguese (n=5/ST19) MDR clone carried merA and/or silA-silE on large non- transferable IncA/C (130-170Kb) or IncR PL (110-140Kb) respectively. MDR S. Typhimurium (n=12; 5 clones; ST19/ST313) carried silA-silE (n=3/DT104 clone) with atypical type I-sul3 integron on IncN PL (135Kb) or merA (n=4) with intI1-oxa30-aadA1/intI1-aadA1 on transferable IncFII PL (120-140Kb). In S. Enteritidis (ST11) only merA (n=2/4) was detected on transferable IncP PL (80Kb) along with intI1-dfrA1-aadA1. In isolates of other MDR clones (n=15/12 serotypes), merA (n=13) and/or silA-silE+pcoD (n=6) were co-located with different Int on large plasmids (>120Kb; IncHI1/IncP/IncI1). The arsB (n=1) and/or terF (n=3) were located on transferable IncHI2 (220Kb) with blaCTX-M-9 or IncP (265kb) (250kb) PL with int1- aadA1 or dfrA1-aadA1/pcoD/silA/merA. Higher CuSO 4 MIC values were obtained in aerobiosis in contrast with anaerobiosis, where a correlation between MICs and Cu R genes was found (MIC 50 =28mM pcoD/silA-silE+ vs 1mM pcoD/silA-silE- ). MICs values for AgNO 3 were higher in anaerobic than aerobic conditions and a slightly difference between silA-silE+ (MIC 50 =0,32/0,25mM) and silA-silE- (MIC 50 =0,25/0,16mM) was observed in both atmospheres. Conclusions. High prevalence of metal tolerance genes associated with increased copper/silver tolerance, and the co-location with ABR genes in different plasmids, suggests that besides antibiotics, metals used in the animal production setting may have contributed for the selection/maintenance of Salmonella clinical relevant clonal lineages.
| Original language | English |
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| Title of host publication | Livro de resumos IJUP'2014 |
| Subtitle of host publication | 7º Encontro de Investigação Jovem da U.Porto |
| Editors | Rui Mendonça |
| Place of Publication | Porto |
| Publisher | Universidade do Porto |
| Pages | 439-439 |
| Number of pages | 1 |
| ISBN (Electronic) | 9789897460333 |
| Publication status | Published - Feb 2014 |
| Externally published | Yes |
| Event | 7º Encontro de Investigação Jovem da Universidade do Porto - Universidade do Porto, Portugal Duration: 12 Feb 2014 → 14 Feb 2014 |
Conference
| Conference | 7º Encontro de Investigação Jovem da Universidade do Porto |
|---|---|
| Abbreviated title | IJUP'14 |
| Country/Territory | Portugal |
| Period | 12/02/14 → 14/02/14 |