The Correlation Between GyrA And CmeR-Box Polymorphism And Fluoroquinolones Resistance In Campylobacter Jejuni Isolates In Central China

Campylobacter jejuni is a major cause of food-borne gastroenteritis worldwide.It can cause human Guillain-Barré syndrome and other diseases,is an important biodegradable environmental symbiotic bacteria.Poultry is one of the main carriers of Campylobacter jejuni,and the contamination of Campylobacter jejuni is an important way for human infection,at the same time,the avian can pass through the food chain,air and excreta to pollute the environment,and thus threaten human health.In recent years in developed countries in Europe and the United States until the developing countries,the over-use of antibiotics in the human population and in animal husbandry has led to an increase in antibiotic-resistant infections,particularly with fluoroquinolones.The results of the drug-sensitive paper diffusion method showed that the antibiotic resistance rate of quinolones such as ciprofloxacin was 99.1%.Therefore,in order to prevent the Campylobacter jejuni disease and the potential threat of its antibiotic resistance to human health,a further Study on the mechanism of quinolone resistance in Campylobacter jejuni in Central China is conducted.In this study,79 C.jejuni strains of quinolone-resistant isolates were analysed by sequence with the DNA gyrase and efflux pump related genes.A number of mutations such as 78,81,86,110,119,120,149,157 and 161 on the gyrA of the gyrase were found,Among which,the 86 mutations(Thr-86-Ile)were present in all quinolone-resistant strains,consistent with the relevant reports.The gyrB gene has multiple nonsense mutations in the isolates.The parC gene was not detected in any of the strains examined.The sequencing of the cmeABC promoter region showed that there were 10 types of CmeR-Box mutations in the CmeR binding domain,and the point insertion and deletion in the reverse repeat region were the first to be found.The MIC test showed that the MIC value of the mutant strain of CmeR-Box was higher than that of the non mutant strain,and the point insertion or deletion strains were the highest(P < 0.05),The results showed that the expression of efflux pump gene cmeA was significantly higher than that of the non mutant strain(P < 0.05)in the CmeR-Box mutant.The results of gel retardation assay showed that the binding of rCmeR protein to CmeR-Box mutant DNA was decreased,and the point insertion and point deletion were the most obvious.It was found that the CmeR-Box mutation resulted in the decrease of the binding ability of cmeABC and the negative regulatory protein Cme R,which led to the upregulation of efflux pump gene expression.The results of this study suggest that all of the quinolone resistance C.jejuni isolates have a reported DNA gyrase mutation in gyrA(Thr-86-Ile),and a series of CmeABC efflux pump promoter mutations were found,among which the insertion and deletion lead to high level quinolone resistance in Campylobacter jejuni.In summary,the molecular mechanism of quinolone resistance in Campylobacter jejuni was preliminarily analyzed,as a result,it will be a target to prevent similar antibiotic resistance mechanism and will really escort human health.