Cristea Violeta Corina, Oprea Mihaela, Neacşu Gabriela, Gîlcă Ramona, Popa Mircea Ioan, Usein Codruţa-Romaniţa
Roum Arch Microbiol Immunol. 2015 Jul-Dec;74(3-4):73-8.
Urinary tract infections (UTI) with Escherichia coli are among the most common infections presenting in general practice. Fluoroquinolones (FQs) are relied on for their empirical therapy but recent reports indicate a concerning increase in the percentage of FQ-resistant E. coli isolates in many countries, including Romania. Sixty E. coli strains with ciprofloxacin resistance and cephalosporin susceptibility isolated from urine specimens of non-hospitalized patients during a five-month period (October 2014 - February 2015) were further analyzed to determine the molecular basis of FQ resistance (i.e. mutations in chromosomal gyrA, gyrB, parC genes and presence of plasmid-borne qnrA, qnrB, qnrS, and aac(6'-Ib-cr genes), the phylogenetic background (i.e. phylogenetic groups A, B1, B2, C, D, E, F or clade I), O25b/ST131 status, and genetic relatedness inferred from the XbaI pulsed-field gel electrophoresis (PFGE) profiles as a measure of isolate-specific genetic composition. The PCR-based phylotyping showed that most strains were assigned to non-B2 phylogenetic groups (i.e. group A/21 strains, group B1/14 strains, group B2/10 strains, group C/8 strains, group D/3 strains, group F/4 strains). Already described chromosomal mutations associated to FQ resistance were found, the strains being double gyrA mutants (i.e. Ser83Leu, Asp87Asn) with one or two parC mutations (e.g. Ala56Thr, Ser80Ile, Glu84Gly). Seven percent of the strains harboured plasmid-borne genes qnrS1 (2 strains) and aac(6'-Ib-cr (2 strains). Based on the PCR results, 15% of the strains were members of the O25b/ST131 clone and possessed the gyrA/parC allele combination which is considered as hallmark of H30 subclone. PFGE genotyping revealed a genetically diverse population of FQ-resistant E. coli. ST131 strains displayed more homogeneous PFGE profiles than non-ST131. The ST131 cluster extended to 77.74% similarity versus 60% overall. These findings underscore the need for ongoing surveillance to capture the complexity of the emerging population of FQ-resistant strains disseminated across our community.
大肠埃希菌引起的尿路感染（UTI）是全科医疗中最常见的感染之一。氟喹诺酮类药物（FQs）被用于经验性治疗，但最近的报告表明，在包括罗马尼亚在内的许多国家，对FQ耐药的大肠埃希菌分离株的百分比出现了令人担忧的上升。对在五个月期间（2014年10月至2015年2月）从非住院患者尿液标本中分离出的60株对环丙沙星耐药但对头孢菌素敏感的大肠埃希菌菌株进行了进一步分析，以确定FQ耐药的分子基础（即染色体gyrA、gyrB、parC基因的突变以及质粒携带的qnrA、qnrB、qnrS和aac(6'-Ib-cr基因的存在）、系统发育背景（即系统发育组A、B1、B2、C、D、E、F或进化枝I）、O25b/ST131状态，以及从XbaI脉冲场凝胶电泳（PFGE）图谱推断的遗传相关性，以此作为分离株特异性遗传组成的一种衡量方法。基于PCR的系统发育分型显示，大多数菌株被归类为非B2系统发育组（即A组/21株、B1组/14株、B2组/10株、C组/8株、D组/3株、F组/4株）。发现了与FQ耐药相关的已描述的染色体突变，这些菌株是双gyrA突变体（即Ser83Leu、Asp87Asn），伴有一个或两个parC突变（如Ala56Thr、Ser80Ile、Glu84Gly）。7%的菌株携带质粒介导的基因qnrS1（2株）和aac(6'-Ib-cr（2株）。根据PCR结果，15%的菌株是O25b/ST131克隆的成员，并拥有被认为是H30亚克隆标志的gyrA/parC等位基因组合。PFGE基因分型显示了一群遗传多样性的FQ耐药大肠埃希菌。ST131菌株的PFGE图谱比非ST131菌株更具同质性。ST131簇的相似度延伸至77.74%，而总体相似度为60%。这些发现强调了持续监测的必要性，以掌握在我们社区中传播的新兴FQ耐药菌株群体的复杂性。
