Resistance Mechanism Of Riemerella Anatipestifer To Macrolides And Lincosamides

Infectious serositis in ducks is a highly contagious disease caused by Riemerella anatipestifer(RA),which can infect ducks,geese,turkeys and various other domestic and wild birds,and occurs worldwide.In production practice,the widespread drug resistance of RA also poses great difficulties for the effective control of the disease.In order to further understand the resistance mechanism of RA,this study investigated the gene function of laboratory-preserved RA to produce macrolide and lincosamide antibiotic resistance based on resistance phenotype and resistance gene detection and whole genome sequencing of RA isolates,and the main results are as follows:1.Detection of macrolide resistance phenotypes and statistical analysis of macrolide resistance genes in RAIn this study,the MIC results of macrolide erythromycin and azithromycin were determined for 573 strains of RA isolated from different parts of China,and the overall statistics of drug resistance and resistance genes were conducted.The main resistance genes were erm F and ere D,and the gene detection rates by whole genome analysis were 69.3%(397/573)and 13.8%(79/573),respectively.2.Statistical analysis of resistance genes to lincosamide antibiotics and the functional study of a new lincosamide nucleoside acyltransferase gene in Riemerella anatipestiferIn this study,the overall statistics of resistance genes causing lincosamides lincomycin and clindamycin were conducted,and the results showed that the main resistance genes of RA to lincosamides were erm F,lnu(H)and lnu(I),and the gene detection rates were 69.3%(397/573),24.6%(141/573),7.7%(44/573)by genome-wide analysis,respectively.In this study,bioinformatics analysis,gene deletion,protein expression and purification,enzyme inactivation yield profile analysis and gene prevalence survey were performed on the AWR41＿00705 gene of RCAD0121 strain.The results showed that the plasmid carrying the gene was able to confer lincosamide resistance to the sensitive strain,and the gene deletion strain changed from lincosamide resistant to sensitive.These results showed that the protein encoded by this gene could cause nucleosidylation of lincomycin and clindamycin and loss of antibiotic efficacy.The gene AWR41＿00705 has less than 75% similarity with other reported genes encoding lincomycin nucleoside acyltransferases,which means it is a new lincomycin resistance gene.The gene and protein are renamed as lnu(I)and Lnu(I),respectively.