Identification of Plasmid-Mediated Quinolone Resistance qnr Genes in Multidrug-Resistant Gram-Negative Bacteria from Hospital Wastewaters and Receiving Waters in the Jinan Area, China

We investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) qnr genes by the polymerase chain reaction (PCR) in antibiotic-resistant bacteria isolates collected from aquatic environments in Jinan during 2 years (2008.3–2009.11). Genes were identified to variant level by PCR restriction fragment length polymorphism analysis or sequencing. qnrA1 , qnrB2 , qnrB4 , qnrB6 , qnrB9 , qnrS1 , and the new qnrB variant qnrB26 were detected in 31 strains from six genera ( Klebsiella spp., Escherichia coli , Enterobacter spp., Proteus spp., Shigella spp., and Citrobacter spp.), four of which contained double qnr genes. Other PMQR genes, aac(6′)-Ib-cr and qepA , were found in 12 (38.7%) and 5 (16.1%) of 31 isolates, respectively; while qepA was found in Shigella spp. for the first time. Eight types of β-lactamase genes and eight other types of resistance genes were also present in the 31 qnr- positive isolates. The detection rate for five β-lactamase genes ( bla TEM , bla CTX , ampR , bla DHA , and bla SHV ) was >45%. Class 1 integrons and complex class 1 integrons were prevalent in these strains, which contained 15 different gene cassette arrays and 5 different insertion sequence common region 1 (IS CR1 )–mediated downstream structures. qnrA1 , qnrB2 , and qnrB6 were present in three IS CR1 -mediated downstream structures: qnrA1–ampR , sapA-like–qnrB2 , and sdr–qnrB6 . We also analyzed the horizontal transferability of PMQR genes and other resistance determinants. The qnr genes and some integrons and resistance genes from 18 (58.1%) of the 31 qnr- positive strains could be transferred to E. coli J53 Azi R or E. coli DH5α recipient strains using conjugation or transformation methods. The results showed that a high number of qnr genes were associated with other resistance genes in aquatic environments in Jinan. This suggests that we should avoid over-using antibiotics and monitor aquatic environments to control the spread of antibiotic resistance genes.