antibiotic resistance plasmidmediated quinolone resistance pmqr genes and ampc gene in two typical municipal wastewater treatment plants antibiotic resistant bacteria and plasmidmediated quinolone resistance genes and ampc gene were investigated for escherichia coli isolates from two typical municipal wastewater treatment plants in both dry and wet seasons by using the antibiotic susceptibility test and pcr assay respectively the results showed that 984 of the isolates 1056 were found resistant to antibiotics tested and 906 showed multiple resistances to at least three antibiotics tetracycline was found to have the highest resistance frequency 708 followed by ampicillin 651 whereas ceftazidime had the lowest resistance frequency of 90 moreover 392 of the e coli isolates were carrying plasmids inti1 had the highest detection rate in the plasmids 381 followed by qnrs ampc qnrb inti2 and aac6ibcr the disinfection process uv and chlorination could significantly reduce the number of bacteria but percentage of the resistant bacteria resistance frequency for each antibiotic mar index and detection rate of the plasmidmediated resistance genes were all found increasing in the effluents of biological units the results of this study showed that a more frequent horizontal gene transfer occurred in the biological units wastewater treatment plants were an important medium for the recombination and dissemination of antibiotic resistance genes in the environment