title: Complex integrons containing qnrB4-ampC (bla(DHA-1)) in plasmids of multidrug-resistant Citrobacter freundii from wastewater.
abstract: 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.
authors: Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.
authors: Grace
authors: G
authors: Yim
authors: Waldan
authors: W
authors: Kwong
authors: Julian
authors: J
authors: Davies
authors: Vivian
authors: V
authors: Miao
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001955:British Columbia; D016971:Citrobacter freundii / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D018432:Drug Resistance, Multiple / Q000235:genetics; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D062065:Wastewater / Q000382:microbiology*; D014871:Water Microbiology; D018440:beta-Lactam Resistance / Q000187:drug effects / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D062065:Wastewater; D001618:beta-Lactamases