Tewawong Nipaporn, Kowaboot Siriporn, Lektrakul Warangkana, Supcharoengoon Utsanee, Watanagul Naiyana, Pitaksajjakul Pannamthip
Faculty of Medical Technology, Rangsit University, Pathum Thani, Thailand.
Department of Microbiology, Nopparat Rajathanee Hospital, Khannayao, Bangkok, Thailand.
PLoS One. 2025 May 30;20(5):e0325175. doi: 10.1371/journal.pone.0325175. eCollection 2025.
Escherichia coli is the major causative agent for urinary tract infections (UTIs), and fluoroquinolones (FQ) are commonly used in the treatment of patients with UTIs. The surge in FQ-resistant E. coli is an important public health threat worldwide. We investigated the prevalence and mechanisms of FQ resistance among FQ-resistant E. coli isolated from UTI patients. A total of 131 FQ-resistant E. coli strains were characterized and broth microdilution assay showed that 108 strains (82.4%) were highly resistant to ciprofloxacin (MIC ≥ 32 μg/mL). All strains were analyzed for plasmid-mediated quinolone resistance (PMQR) genes, with 37 (28.2%) testing positive. Among the PMQR genes detected, aac(6')-Ib-cr was the most frequent, found in 30 strains (22.9%), followed by qnrS in 10 strains (7.6%) and qnrB in 1 strain (0.8%). PCR assay showed that all carried acrA, acrB, and tolC genes, but 33 strains (25.2%) revealed at least 4-fold reduction in ciprofloxacin MIC when using PAβN and CCCP as efflux pump inhibitors, indicating the role of the AcrAB efflux pump in ciprofloxacin resistance in these strains. The 19 strains of high-level ciprofloxacin-resistant E. coli were selected to determine the target enzyme alteration by PCR assay and DNA sequencing. Genetic analysis revealed that 16 strains (84.2%) had double mutations in gyrA (S83L and D87 to N or Y) with single mutation in parC (S80I), while 3 strains (15.8%) had double mutations in gyrA (S83L and D87 to N or Y) and parC (S80I and E84 to G or V). The positive efflux activity was linked to increased MIC values of ciprofloxacin (P < 0.001). Overall, the carriage of PMQR genes, efflux activity, and target mutations across E. coli strains contribute to ciprofloxacin resistance, a result that may necessitate a reassessment of the antibiotics in use for empirical UTIs therapy.
大肠埃希菌是尿路感染（UTIs）的主要致病菌，氟喹诺酮类药物（FQ）常用于治疗UTIs患者。耐FQ大肠埃希菌的激增是全球重要的公共卫生威胁。我们调查了从UTIs患者中分离出的耐FQ大肠埃希菌对FQ耐药的流行情况及机制。共对131株耐FQ大肠埃希菌进行了鉴定，肉汤微量稀释法显示108株（82.4%）对环丙沙星高度耐药（MIC≥32μg/mL）。对所有菌株进行质粒介导的喹诺酮耐药（PMQR）基因分析，37株（28.2%）检测呈阳性。在检测到的PMQR基因中，aac(6')-Ib-cr最为常见，在30株（22.9%）中发现，其次是qnrS在10株（7.6%）中，qnrB在1株（0.8%）中。PCR检测显示所有菌株均携带acrA、acrB和tolC基因，但当使用PAβN和CCCP作为外排泵抑制剂时，33株（25.2%）的环丙沙星MIC至少降低了4倍，表明AcrAB外排泵在这些菌株对环丙沙星耐药中发挥作用。选择19株高水平环丙沙星耐药的大肠埃希菌通过PCR检测和DNA测序来确定靶酶改变。基因分析显示，16株（84.2%）在gyrA中有双突变（S83L和D87突变为N或Y），在parC中有单突变（S80I），而3株（15.8%）在gyrA中有双突变（S83L和D87突变为N或Y），在parC中有双突变（S80I和E84突变为G或V）。阳性外排活性与环丙沙星MIC值升高相关（P<0.001）。总体而言，PMQR基因的携带、外排活性和靶基因突变在大肠埃希菌菌株中共同导致了环丙沙星耐药，这一结果可能需要重新评估用于经验性UTIs治疗的抗生素。
