title: Metal tolerance in emerging clinically relevant multidrug-resistant Salmonella enterica serotype 4,[5],12:i:- clones circulating in Europe.
abstract: The occurrence of acquired metal tolerance genes in emerging MDR Salmonella enterica serotype 4,[5],12:i:- clones was assessed and their associated platforms and tolerance phenotype were characterised. Salmonella 4,[5],12:i:- from different sources belonging to European, Spanish and Southern European clones were studied. Screening for copper (pcoA-pcoD/tcrB), silver/copper (silA-silE), mercury (merA), arsenic (arsB) and tellurite (terF) tolerance genes was performed by PCR/sequencing. CuSO(4)/AgNO(3) MICs were determined in aerobic/anaerobic atmospheres by agar dilution. Conjugation assays, genomic location and plasmid analysis were performed by standard procedures. Most isolates from European (98%) and Spanish (74%) clones carried silA-silE, contrasting with the Southern European clone (26%). merA/62% (European and Spanish clones) and pcoA-pcoD/50% (European clone) were also detected. merA±pco+sil were chromosomally located in the European clone, whereas in Spanish and Southern European clones sil±merA were within plasmids, both with antibiotic resistance genes. The pcoA-pcoD/silA-silE(+) isolates showed higher MICCuSO(4) in anaerobiosis than those without these genes (MIC(50)=24-28 vs. 2 mM). Different MICAgNO(3) of silA-silE(+) (MIC(50)=0.25 mM) and silA-silE(-)(MIC(50)=0.16 mM) isolates were observed in both atmospheres, with an MIC increment after prior exposure to silver (>3 vs. 0.08-0.125 mM) in aerobiosis. A high frequency of copper and silver tolerance, particularly among the two major Salmonella 4,[5],12:i:- MDR clones (European/Spanish) circulating in Europe and causing human infections, might facilitate adaptation/expansion of these strains in metal-contaminated environments, particularly copper in anaerobiosis. Furthermore, metal toxic concentrations in food-animal environments can contribute to persistence of genetic platforms carrying metal/antibiotic resistance genes in this foodborne zoonotic pathogen.
authors: UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
authors: Joana
authors: J
authors: Mourão
authors: UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
authors: Carla
authors: C
authors: Novais
authors: Laboratório Nacional de Referência de Infecções Gastrointestinais, Departamento de Doenças Infecciosas, Instituto Nacional de Saúde Dr Ricardo Jorge, Lisbon, Portugal.
authors: Jorge
authors: J
authors: Machado
authors: UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
authors: Luísa
authors: L
authors: Peixe
authors: UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal; Faculdade de Ciências da Nutrição e Alimentação, Universidade do Porto, Porto, Portugal. Electronic address: patriciaantunes@fcna.up.pt.
authors: Patrícia
authors: P
authors: Antunes
mesh_terms: D000818:Animals; D003227:Conjugation, Genetic; D024901:Drug Resistance, Multiple, Bacterial; D004361:Drug Tolerance; D005060:Europe; D005516:Food Microbiology; D005798:Genes, Bacterial / Q000235:genetics; D006801:Humans; D019216:Metals, Heavy / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D012480:Salmonella Infections / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000382:microbiology; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D065288:Serogroup
chemical_list: D019216:Metals, Heavy
keywords: Biocides; Copper; Multidrug resistance; Salmonella enterica Typhimurium monophasic variant; Silver