Abstract
This study aimed to investigate the occurrence of biofilm-forming extended-spectrum beta-lactamase (ESBL)-producing enteric bacteria in hospital wastewater and to evaluate their antibiotic resistance behaviour and transferability of the plasmid-encoded bla(CTX-M) gene in biofilm. ESBL production was confirmed using the combined disc test and Etest. Amplification of bla(CTX-M) was performed by PCR. Antibiotic susceptibility was evaluated using the disc diffusion assay and broth dilution method. Transfer of bla(CTX-M) in planktonic and biofilm state was performed by broth mating and filter mating experiments, respectively. Among 110 enteric bacteria, 24 (21.8%) isolates belonging to Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae were found to produce ESBL and formed varying levels of biofilm in vitro. Presence of bla(CTX-M) was detected in 18 (75%) ESBL-producing isolates. A many fold increase in resistance to antibiotics was observed in biofilm. Among ESBL-producers, seven isolates could transfer the bla(CTX-M) gene by conjugation, with transfer frequencies ranging from 2.22 x 10(-4) to 7.14 x 10(-2) transconjugants/recipient cell in the planktonic state and from 3.04 x 10(-3) to 9.15 x 10(-1) in biofilm. The transfer frequency of bla(CTX-M) was significantly higher in biofilm compared with the planktonic state, and co-transfer of ciprofloxacin resistance was also detected in five isolates. This study demonstrates that biofilm-forming ESBL-producing enteric bacteria with a greater transfer frequency of resistance genes will lead to frequent dissemination of beta-lactam and fluoroquinolone resistance genes in environmental settings. The emergence and spread of such multidrug resistance is a serious threat to animal and public health. (C) 2016 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.