Infante Victor Hugo Pacagnelli, Conceição Natália, de Oliveira Adriana Gonçalves, Darini Ana Lúcia da Costa
Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903, Ribeirão Preto, São Paulo, Brazil.
Instituto de Ciências Biológicas e Naturais, Universidade Federal do Triângulo Mineiro, 38015-050, Uberaba, Minas Gerais, Brazil
FEMS Microbiol Lett. 2016 Apr;363(7). doi: 10.1093/femsle/fnw044. Epub 2016 Feb 22.
The aim of the present study was to verify whether penicillin-resistant, ampicillin-susceptible Enterococcus faecalis (PRASEF) occurred in Brazil prior to the beginning of the 21st century, and to verify whether ampicillin susceptibility can predict susceptibility to other β-lactams in E. faecalis with this inconsistent phenotype. The presence of polymorphisms in the pbp4 gene and genetic diversity among the isolates were investigated. Of 21 PRASEF analyzed, 5 (23.8%) and 4 (19.0%) were imipenem and piperacillin resistant simultaneously by disk diffusion and broth dilution respectively, contradicting the current internationally accepted standards of susceptibility testing. Sequencing of pbp4 gene revealed an amino acid substitution (Asp-573→Glu) in all PRASEF isolates but not in the penicillin-susceptible, ampicillin-susceptible E. faecalis. Most PRASEF (90.5%) had related pulsed-field gel electrophoresis profiles, but were different from other PRASEF described to date. Results demonstrate that penicillin-resistant, ampicillin-susceptible phenotype was already a reality in the 1990s in E. faecalis isolates in different Brazilian states, and some of these isolates were also imipenem- and piperacillin-resistant; therefore, internationally accepted susceptibility criteria cannot be applied to these isolates. According to pbp4 gene sequencing, this study suggests that a specific amino acid substitution in pbp4 gene found in all PRASEF analyzed is associated with penicillin resistance.
本研究的目的是验证耐青霉素、对氨苄西林敏感的粪肠球菌（PRASEF）在21世纪初之前是否在巴西出现，并验证氨苄西林敏感性能否预测具有这种不一致表型的粪肠球菌对其他β-内酰胺类药物的敏感性。研究了pbp4基因中的多态性以及分离株之间的遗传多样性。在分析的21株PRASEF中，分别有5株（23.8%）和4株（19.0%）通过纸片扩散法和肉汤稀释法同时对亚胺培南和哌拉西林耐药，这与目前国际上公认的药敏试验标准相矛盾。pbp4基因测序显示，所有PRASEF分离株都有一个氨基酸替换（Asp-573→Glu），而在对青霉素敏感、对氨苄西林敏感的粪肠球菌中则没有。大多数PRASEF（90.5%）具有相关的脉冲场凝胶电泳图谱，但与迄今描述的其他PRASEF不同。结果表明，耐青霉素、对氨苄西林敏感的表型在20世纪90年代在巴西不同州的粪肠球菌分离株中就已经存在，其中一些分离株还对亚胺培南和哌拉西林耐药；因此，国际上公认的药敏标准不能应用于这些分离株。根据pbp4基因测序，本研究表明，在所有分析的PRASEF中发现的pbp4基因中的特定氨基酸替换与青霉素耐药有关。
