title: Penicillin-resistant, ampicillin-susceptible Enterococcus faecalis of hospital origin: pbp4 gene polymorphism and genetic diversity.
abstract: Despite the spread of penicillin-resistant, ampicillin-susceptible Enterococcus faecalis (PRASEF) isolates in diverse countries, the mechanisms leading to this unusual resistance phenotype have not yet been investigated. The aim of this study was to evaluate whether polymorphism in the pbp4 gene is associated with penicillin resistance in PRASEF isolates and to determine their genetic diversity. E. faecalis isolates were recovered from different clinical specimens of hospitalized patients from February 2006 to June 2010. The β-lactam minimal inhibitory concentrations (MICs) were determined by E-test®. The PCR-amplified pbp4 gene was sequenced with an automated sequencer. The genetic diversities of the isolates were established by PFGE (pulsed-field gel electrophoresis) and MLST (multilocus sequencing typing). Seventeen non-producing β-lactamase PRASEF and 10 penicillin-susceptible, ampicillin-susceptible E. faecalis (PSASEF) strains were analyzed. A single-amino-acid substitution (Asp-573→Glu) in the penicillin-binding domain was significantly found in all PRASEF isolates by sequencing of the pbp4 gene but not in the penicillin-susceptible isolates. In contrast to the PSASEF isolates, a majority of the PRASEFs had similar PFGE profiles. Six representative PRASEF isolates were resolved by MLST into ST9 and ST524 and belong to the globally dispersed clonal complex 9 (CC9). In conclusion, it appears quite likely that the amino acid alteration (Asp-573→Glu) found in the PBP4 of the Brazilian PRASEF isolates may account for their reduced susceptibility to penicillin, although other resistance mechanisms remain to be investigated.
authors.affiliation: Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil; Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Natália
authors.initials: N
authors.lastname: Conceição
authors.affiliation: Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil.
authors.forename: Lucas Emanuel Pinheiro
authors.initials: LE
authors.lastname: da Silva
authors.affiliation: Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Ana Lúcia da Costa
authors.initials: AL
authors.lastname: Darini
authors.affiliation: Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Pitondo-Silva
authors.affiliation: Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil. Electronic address: agoliveira@dcb.uftm.edu.br.
authors.forename: Adriana Gonçalves
authors.initials: AG
authors.lastname: de Oliveira
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D003428:Cross Infection / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics*; D014644:Genetic Variation; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D010403:Penicillin Resistance / Q000235:genetics; D046915:Penicillin-Binding Proteins / Q000235:genetics*; D010406:Penicillins / Q000494:pharmacology; D001618:beta-Lactamases
chemical_list: D046915:Penicillin-Binding Proteins; D010406:Penicillins; D000667:Ampicillin; D001618:beta-Lactamases
keywords: E. faecalis; MLST; PFGE; Penicillin-binding proteins; Penicillin-resistance