LAUSR

Dissemination of antibiotic-resistant genes (ARGs) from hospital wastewaters (HWWs) is facilitated by the horizontal gene transfer (HGT) and involves association of ARGs with mobile genetic elements (MGEs). In our previous study, HWWs were found to have relatively high copy numbers of ARGs aadA, tetA, cmlA, sul1, and qnrS . In this study, therefore, the same HWWs were also monitored for 3 MGEs class 1 integron ( int I1) , insertion sequence common region 1 (IS CR1 ) and conjugative transposon Tn 916/ Tn 1545 by using quantitative polymerase chain reaction. The gene int I1 with 7.4 × 10 2 average copy number/mL was found to be the most prevalent MGE and was up to two orders of magnitude higher than IS CR1 (5.5 × 10 0 average copy number/mL, p  < 0.05) and Tn 916 /Tn 1545 (2.3 × 10 0 average copy number/mL, p  < 0.05) in all HWWs tested. Positive correlation between int I1 and the aadA, tetA, cmlA and sul1 genes indicated that the MGEs harbouring class1 integron most likely played major role in co-selecting all these ARGs together.