Abstract：
Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales are a major public health problem, and wastewater from municipal wastewater treatment plants (WWTPs) is a potential means of spreading them into the environment and community. Our objective was to isolate ESBL-producing E. coli and other Enterobacterales from wastewater after treatment at Croatia\'s largest WWTP and to characterize these isolates by phenotypic and genotypic testing. Of the 200 bacterial isolates, 140 were confirmed as Enterobacterales by MALDI-TOF MS, with Escherichia coli and Klebsiella spp. predominating (69% and 7%, respectively). All 140 enterobacterial isolates were multidrug-resistant (MDR) and produced ESBLs. The most prevalent ESBL genes among the isolates tested were blaCTX-M-15 (60%), blaTEM-116 (44%), and blaCTX-M-3 (13%). Most isolates (94%) carried more than one ESBL gene in addition to blaCTX-M. Genes encoding plasmid-mediated AmpC, most notably blaEBC, were detected in 22% of isolates, whereas genes encoding carbapenemases (blaOXA-48, blaNDM-1, blaVIM-1) were less represented (10%). In E. coli, 9 different sequence types (ST) were found, with the emerging high-risk clones ST361 (serotype A-O9:H30) and pandemic ST131 (serotype B2-O25:H4) predominating (32% and 15%, respectively). Other high-risk E. coli clones included ST405 (3%), ST410 (3%), CC10 (3%), ST10 (3%), and ST38 (2%), and emerging clones included ST1193 (2%) and ST635 (2%). Whole-genome sequencing of three representative E. coli from two dominant clone groups (ST361 and ST131) and one extensively drug-resistant K. oxytoca revealed the presence of multiple plasmids and resistance genes to several other antibiotic classes, as well as association of the blaCTX-M-15 gene with transposons and insertion sequences. Our findings indicate that treated municipal wastewater contributes to the spread of emerging and pandemic MDR E. coli clones and other enterobacterial strains of clinical importance into the aquatic environment, with the risk of reintroduction into humans.
摘要：
产超广谱β-内酰胺酶（ESBL）的肠杆菌是一个主要的公共卫生问题，市政污水处理厂（WWTP）的废水是将其传播到环境和社区的潜在手段。我们的目标是在克罗地亚最大的污水处理厂处理后，从废水中分离出产ESBL的大肠杆菌和其他肠杆菌，并通过表型和基因型测试对这些分离株进行表征。在200个细菌分离物中,140例被MALDI-TOF确认为肠杆菌，大肠杆菌和克雷伯菌属。占主导地位(69%和7%，分别)。所有140株肠杆菌分离株均为多重耐药（MDR）并产生ESBLs。测试的分离株中最普遍的ESBL基因是blaCTX-M-15（60％），blaTEM-116(44%),和blaCTX-M-3（13%）。除blaCTX-M外，大多数分离株（94％）还携带一个以上的ESBL基因。编码质粒介导的AmpC的基因，最值得注意的是blaEBC,在22%的分离株中检测到，而编码碳青霉烯酶（blaOXA-48，blaNDM-1，blaVIM-1）的基因表达较少（10％）。在大肠杆菌中，发现了9种不同的序列类型（ST），新兴的高风险克隆ST361（血清型A-O9：H30）和大流行ST131（血清型B2-O25：H4）占主导地位（32％和15％，分别)。其他高风险大肠杆菌克隆包括ST405（3％），ST410（3%），CC10（3%），ST10（3%），和ST38（2%），新出现的克隆包括ST1193(2%)和ST635(2%)。来自两个优势克隆组（ST361和ST131）的三个代表性大肠杆菌和一个广泛耐药的K.oxytoca的全基因组测序显示存在多个质粒和对其他几种抗生素类别的抗性基因，以及blaCTX-M-15基因与转座子和插入序列的关联。我们的发现表明，经过处理的城市废水有助于新出现和大流行的MDR大肠杆菌克隆和其他具有临床重要性的肠杆菌菌株传播到水生环境中。有重新引入人类的风险。
