Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
Can J Microbiol. 2013 Feb;59(2):110-6. doi: 10.1139/cjm-2012-0576. Epub 2012 Nov 29.
Microbial populations in wastewater treatment plants (WWTPs) are increasingly being recognized as environmental reservoirs of antibiotic resistance genes. PCR amplicons for plasmid-mediated quinolone resistance determinants qnrA, qnrB, and qnrS were recorded in samples from a WWTP in Vancouver, British Columbia. Six strains of ciprofloxacin-resistant Citrobacter freundii were isolated and found to carry mutations in gyrA and parC, as well as multiple plasmid-borne resistance genes, collectively including qnrB; aac(6')-Ib-cr; β-lactamase-encoding genes from molecular classes A (blaTEM-1), C (ampC), D (blaOXA-1, blaOXA-10); and genes for resistance to 5 other types of antibiotics. In 3 strains, large (>60 kb) plasmids carried qnrB4 and ampC as part of a complex integron in a 14 kb arrangement that has been reported worldwide but, until recently, only among pathogenic strains of Klebsiella. Analysis of single-nucleotide polymorphisms in the qnrB4-ampC regions infers 2 introductions into the WWTP environment. These results suggest recent passage of plasmid-borne fluoroquinolone and β-lactam resistance genes from pathogens to bacteria that may be indigenous inhabitants of WWTPs, thus contributing to an environmental pool of antibiotic resistance.
污水处理厂 (WWTP) 中的微生物种群越来越被认为是抗生素耐药基因的环境储库。在不列颠哥伦比亚省温哥华的一个 WWTP 的样本中记录了质粒介导的喹诺酮类耐药决定因子 qnrA、qnrB 和 qnrS 的 PCR 扩增子。从耐环丙沙星的弗氏柠檬酸杆菌中分离出 6 株菌株，发现它们携带 gyrA 和 parC 突变，以及多种质粒携带的耐药基因，包括 qnrB、aac(6')-Ib-cr、分子类别 A（blaTEM-1）、C（ampC）、D（blaOXA-1、blaOXA-10）的β-内酰胺酶编码基因；以及对其他 5 种类型抗生素的耐药基因。在 3 株菌中，大 (>60 kb) 质粒携带 qnrB4 和 ampC，作为一种已在全球范围内报道但直到最近才仅在致病性克雷伯氏菌中发现的复杂整合子的一部分，其排列为 14 kb。qnrB4-ampC 区域的单核苷酸多态性分析推断出有 2 次质粒介导的氟喹诺酮和β-内酰胺耐药基因从病原体转移到 WWTP 环境中的情况。这些结果表明，来自病原体的质粒携带的氟喹诺酮和β-内酰胺类耐药基因最近传递给了可能是 WWTP 本土居民的细菌，从而导致了抗生素耐药性的环境库。
