title: Characterisation of plasmids implicated in the mobilisation of extended-spectrum and AmpC β-lactamase genes in clinical Salmonella enterica isolates and temporal stability of the resistance genotype.
abstract: Plasmids implicated in the mobilisation of β-lactamase genes in extended-spectrum β-lactamase (ESBL)- and AmpC-producing Salmonella enterica isolates recovered from three Spanish hospitals were characterised. The temporal stability of these plasmids and of the resistance phenotype without antimicrobial pressure was also assessed in the laboratory setting. The resistance determinants and their genetic environments were characterised by PCR sequencing, and their genomic location was analysed by S1 nuclease pulsed-field gel electrophoresis (PFGE) and I-CeuI PFGE, followed by Southern blot hybridisation. The 11 S. enterica studied strains carried blaCTX-M-9 (serovar Virchow, 2 isolates), blaCTX-M-10 (Virchow, 2), blaCTX-M-14 (Enteritidis, 1), blaCTX-M-15 (Gnesta and S. enterica group C, 2), blaSHV-2 (Livingstone, 1), blaSHV-12 (Enteritidis, 1) and blaCMY-2 (Bredeney, 2). The ISEcp1-blaCTX-M-14-IS903 and ISEcp1-blaCTX-M-15-orf477 genetic structures were detected. IncI1 and IncA/C plasmids carried blaCTX-M-14, blaCTX-M-15, blaSHV-2, blaSHV-12 and blaCMY-2 genes. blaCTX-M-9 included in an In60 complex integron and blaCTX-M-10 linked to a phage-related element were found in non-typeable plasmids. Conjugation and temporal stability experiments were performed in vitro through daily passages (100 days) in the absence of antimicrobial pressure. In the stability experiments, 5 of the 11 tested isolates lost the ESBL or AmpC plasmidic genes and this was associated with concomitant loss of the whole or partial plasmid. In conclusion, successful plasmids belonging to different Inc groups mobilise ESBL- and AmpC-encoding genes in S. enterica. Loss of ESBL/AmpC genes in the absence of antimicrobial pressure might explain the low prevalence of these β-lactamases among Salmonella isolates.
authors.affiliation: Área de Bioquímica y Biología Molecular, Universidad de La Rioja, Av. Madre de Dios 51, Logroño, La Rioja, Spain.
authors.forename: María
authors.initials: M
authors.lastname: de Toro
authors.forename: Patricia
authors.initials: P
authors.lastname: García
authors.forename: Irene
authors.initials: I
authors.lastname: Rodríguez
authors.forename: Beatriz
authors.initials: B
authors.lastname: Rojo-Bezares
authors.forename: Reiner
authors.initials: R
authors.lastname: Helmuth
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Sáenz
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Rodicio
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
authors.forename: Carmen
authors.initials: C
authors.lastname: Torres
mesh_terms: D015139:Blotting, Southern; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D022761:Gene Transfer, Horizontal; D042822:Genomic Instability; D005838:Genotype; D006761:Hospitals; D006801:Humans; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012480:Salmonella Infections / Q000382:microbiology; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013030:Spain; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001618:beta-Lactamases
keywords: ESBL; Plasmid; Salmonella enterica; bla(CMY); bla(CTX-M); bla(SHV)