This study was undertaken to assess the prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) among blow fly (Chrysomya megacephala) populations in Northern Thailand. Of 600 blow flies collected from rural (n = 400) and urban (n = 200) areas, 334 blow flies carried ESBL-EC (55.7%). Prevalence of ESBL-EC in blow flies captured from rural areas was significantly higher than that from urban region (72.5% vs. 22.0%, p < 0.001). Susceptibility tests revealed that 68.6% of ESBL-EC possessed multidrug-resistant phenotypes. Coresistance to gentamicin (85%) was common, while resistance to ciprofloxacin was relatively low (18.0%). Of the 334 isolates, 253 isolates (75.7%) harbored bla_CTX-M, in which bla_{CTX-M group 1} was predominant (56.5%), followed by bla_{CTX-M group 9} (39.1%). Interestingly, a single isolate was found to carry bla_CTX-M-5, which resided on the IncA/C conjugative plasmid. This is the first report of bla_CTX-M-5 from Thailand and its first identification in blow fly. Pulsed field gel electrophoresis (PFGE) demonstrated high genetic diversity among ESBL-EC isolates. Nevertheless, identical and closely related PFGE profiles were detected among isolates within the same regions and the regions which are several kilometers apart, suggesting that clonal transmission has occurred. Moreover, epidemiologically related isolates were observed between ESBL-EC from blow flies and human intestinal tract. This study provides evidences that blow flies, C. megacephala, are important reservoirs for ESBL-EC and could potentially act as vectors for the spread of ESBL-EC in a Thai community.

中文翻译：

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blaCTX-M 的流行率和携带 blaCTX-M-5 的大肠杆菌在大头金蝇（双翅目：Calliphoridae）中的出现，泰国北部

本研究旨在评估泰国北部苍蝇（Chrysomya megacephala）种群中产超广谱β-内酰胺酶（ESBL）的大肠杆菌（ESBL-EC）的流行情况。在从农村 ( n  = 400) 和城市 ( n  = 200) 地区收集的 600 只苍蝇中，334 只苍蝇携带 ESBL-EC (55.7%)。ESBL-EC 在农村地区捕获的苍蝇中的流行率显着高于城市地区（72.5% 对 22.0%，p  < 0.001）。药敏试验显示 68.6% 的 ESBL-EC 具有多重耐药表型。对庆大霉素的耐药性 (85%) 很常见，而对环丙沙星的耐药性相对较低 (18.0%)。在 334 个分离株中，253 个分离株 (75.7%) 含有bla _CTX-M，其中bla _{CTX-M 组 1}占优势（56.5%），其次是bla _{CTX-M 组 9}（39.1%）。有趣的是，发现单个分离物携带bla _CTX-M-5，它位于 IncA/C 接合质粒上。这是bla _CTX-M-5的第一份报告来自泰国，并首次在吹蝇中鉴定。脉冲场凝胶电泳 (PFGE) 显示 ESBL-EC 分离株之间的高遗传多样性。然而，在同一地区和相距几公里的地区内的分离株中检测到相同且密切相关的 PFGE 谱，表明发生了克隆传播。此外，在来自苍蝇和人类肠道的 ESBL-EC 之间观察到了流行病学相关的分离株。这项研究提供的证据表明，苍蝇C. megacephala是 ESBL-EC 的重要储存库，并且可能作为 ESBL-EC 在泰国社区中传播的载体。