Prevalence of out-of-hospital prevalence of carbapenem-resistance genes and influences of antibiotics with different antibacte-rial mechanisms on the genes spread
Objective To analyze the distribution of carbapenem-resistant strains and the transmission mode of resistance genes in the bacteria strains from urinary system of the individuals outside hospitals,and further explore the impacts of the antibiotics with different antibacterial mechanisms on the conjugation transfer of resistant plasmids.Methods The imipenem-resistant strains from 991 non-re-petitive urine samples of healthy individuals were screened for determining the carbapenem-resistance genotypes.Using the multilocus sequence typing(MLST)method,the main carbapenem-resistant strains were classified to determine the phylogenetic relationship be-tween different sequence types(STs)and reveal the transmission mode of resistance genes in the individuals outside hospitals.The conjugation experiment was used to analyze the effects of different sub-inhibitory concentrations of ampicillin,ciprofloxacin,and genta-micin on the conjugation efficiency of resistant plasmids in the bacteria of donor and/or recipient at different times.Results A total of 18 non-repetitive carbapenem-resistant strains(1.82％,18/991)were detected in healthy individuals outside hospitals,among which Escherichia coli(E.coli)(44.44％,8/18)was the main strain with main genotype being blaKPC-2(7/8).MLST showed that the 7 strains of E.coli with blaKPC-2 genotype belonged to ST-10,ST-101,ST-131,ST-405,ST-410,ST-1193,and ST-2562,respectively.Homologous clustering analysis showed that the type of the 7 E.coli strains exhibited high diversity.The range of joint efficiency was(1.59±0.20)× 10-4 to(4.01±1.31)× 10-4.The highest conjugation efficiency was observed in the donor bacteria treated with 1/8 of MIC of antibiotics for 9 hours,and the conjugation efficiency most significantly increased compared to the group without antibiotic treat-ment.Three antibiotics with different mechanisms of action could all improve conjugation efficiency,among which ampicillin exhibited the most significant improvement.Conclusion In this study,the genotype of carbapenem-resistant Escherichia coli(CREC)was mainly blaKPC-2 with a main mode of horizontal transmission.Antibiotics with sub-inhibitory concentrations could promote the conjugation transfer of the resistant plasmid.There may be significant differences in the effects of antibiotics with different mechanisms of action and different antibiotic stress conditions on the conjugation efficiency.
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