Service of Microbiology, University Hospital Marqués de Valdecilla-IDIVAL, Avenida de Valdecilla s/n, 39008, Santander, Spain.
Service of Microbiology, University Hospital Marqués de Valdecilla-IFIMAV, Avenida de Valdecilla s/n, 39008, Santander, Spain.
Eur J Clin Microbiol Infect Dis. 2018 Aug;37(8):1475-1480. doi: 10.1007/s10096-018-3273-z. Epub 2018 May 13.
The aims of this study were to determine the correlation of mutations in the ftsI gene (coding for PBP3) of Haemophilus influenzae with aminopenicillin resistance and to evaluate the 2017 European Committee for Antibiotic Susceptibility Testing (EUCAST) guidelines for clinical categorization of ampicillin, amoxicillin, and amoxicillin-clavulanate for strains with mutated PBP3 conferring resistance (rPBP3). A panel of 91 H. influenzae isolates was genetically characterized by sequencing of the fstI gene. For all the studied isolates, a screening with benzylpenicillin 1U (BP1) was carried out and minimum inhibitory concentrations (MICs) of ampicillin, amoxicillin, and amoxicillin-clavulanate were tested and interpreted according to EUCAST recommendations. ftsI sequence analysis revealed a total of 14 different amino acid substitutions in PBP3. The substitution patterns most commonly observed were [D350N, M377I, A502V, N526K] among the bla-positive rPBP3 strains (37.5%) and [D350N, A502T, N526K] among the bla-negative rPBP3 strains (24.5%). Screening with BP1 was able to correctly categorize 100% of the bla-negative sPBP3 strains, 100% of the bla-positive strains, and 92% of the bla-negative rPBP3 ones. Only 29% of the bla-negative rPBP3 strains evaluated displayed ampicillin MICs above the current EUCAST resistant breakpoint defined at 1 μg/ml. The PBP3 substitution patterns of the strains evaluated are similar to the ones observed in previous Spanish and European studies. Although the screening with BP1 proved to be adequate in the detection of bla-negative rPBP3 strains, these cannot be reliably identified by current 2018 EUCAST breakpoints for ampicillin.
本研究旨在确定流感嗜血杆菌 ftsI 基因（编码 PBP3）突变与氨苄西林耐药性的相关性，并评估 2017 年欧洲抗菌药物敏感性测试委员会（EUCAST）针对具有突变 PBP3 （rPBP3）的菌株的氨苄西林、阿莫西林和阿莫西林-克拉维酸的临床分类指南。通过 ftsI 基因测序对 91 株流感嗜血杆菌分离株进行遗传特征分析。对所有研究分离株进行了青霉素 1U（BP1）的筛选，并根据 EUCAST 建议测试和解释了氨苄西林、阿莫西林和阿莫西林-克拉维酸的最低抑菌浓度（MIC）。ftsI 序列分析显示 PBP3 中共有 14 种不同的氨基酸取代。在 bla 阳性 rPBP3 菌株中最常见的取代模式为 [D350N、M377I、A502V、N526K]（37.5%），在 bla 阴性 rPBP3 菌株中最常见的取代模式为 [D350N、A502T、N526K]（24.5%）。BP1 筛选能够正确分类 100%的 bla 阴性 sPBP3 菌株、100%的 bla 阳性菌株和 92%的 bla 阴性 rPBP3 菌株。仅 29%的 bla 阴性 rPBP3 菌株的氨苄西林 MIC 值超过当前 EUCAST 定义的 1μg/ml 的耐药折点。评估的菌株的 PBP3 取代模式与以前在西班牙和欧洲的研究中观察到的模式相似。尽管 BP1 筛选在检测 bla 阴性 rPBP3 菌株方面证明是足够的，但这些菌株不能通过当前 2018 年 EUCAST 针对氨苄西林的折点可靠地识别。
