Objective The prevalence of disinfectant resistance genes and the relationship between resistance to disinfectants and antibiotics in Escherichia coli recovered from the swine and farm environment were investigated.
Method A total of 130 samples collected from swine manure, air, pond water, soil and farm workers were screened for the presence of qacE, qacE△1, qacF, qacG, emrE, sugE(c), sugE(p), mdfA and ydgE/ydgF resistance genes. The susceptibilities of E. coli strains to four disinfectants and ten common antibiotics were determined using the agar dilution method.
Result and conclusion Ninety-seven strains of E. coli were obtained from 130 samples with detection frequency of 74.6%. All E. coli isolates showed reduced susceptibility to four disinfectants. The minimum inhibitory concentrations (MICs) of benzalkonium chloride (BC) and cetyltrimethy ammonium bromide (CTAB) against E. coli were higher than those of triclosan (TCS) and chlorhexidine (CL). The percent of E. coli strains, which displayed multi-drug resistant phenotypes, was 87.6% (85/97), and the resistance rates of sulfamethoxazole/trimethoprim (S/T), doxycycline(DOX), nalidixic acid (NAL), cefotaxime (CTX) and florfenicol (FFC) were high(68%-88%). However, the disinfectant resistance genes were less prevalent (2.1%-20.6%), with the most prevalent of qacE△1 found in 97 E. coli strains. There was a positive correlation between antimicrobial resistance and high MICs of quaternary ammonium compounds. The close relationship between the detection rate of disinfectant resistance genes and six antimicrobials resistance in E. coli strains was found, which resisted S/T, NAL, ciprofloxacin (CIP), cefoxitin (FOX), AMK and CS, respectively. The co-resistance E. coli poses a challenge to environmental management. Therefore, regulation of using antibiotics and disinfectants is urgently needed in order to slow down the emergence of drug-resistant bacteria.
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