Molecular Epidemiological Investigation And Drug Resistance Gene Screening Of Mycoplasma Synoviae

Mycoplasma synoviae（M.synoviae）is a kind of Mycoplasma whose size is between bacteria and viruses.M.synoviae often causes subclinical infection in chickens,which can develop into respiratory diseases or infectious synovitis,resulting in slow growth,obvious claudication,decreased egg production rate,abnormal eggshell apex（EAA）and low immunity.With the decrease of immunity,M.synoviae will also be co-infected the chickens with other pathogens such as Newcastle disease virus and infectious bronchitis virus to increase the mortality,which has caused potential huge economic losses to poultry industry in China and all the global.In this study,the trachea and sternum mucosa of chickens suspected to be infected with M.synoviae in Anhui,Henan and Hubei provinces in Central China from 2019 to 2021 were collected,and the infections of M.synoviae was statistically investigated,which provided a theoretical basis and technical support for the establishment of an epidemiological system in Central China.Meanwhile,molecular epidemiological investigation and analysis of M.synoviae were carried out to understand the genetic variation and drug resistance genes of M.synoviae strains.In recent three years,the infection rate of M.synoviae in Anhui,Henan and Hubei provinces has been mastered.A total of 237 samples were collected from the three provinces in the past three years,96 strains of M.synoviae were isolated and identified,and the infection rate was about 40.5 %.According to the highly conserved region of vlh A,the genotypes were determined to be A type for 2 strains,D type for 2 strains,E type for 7 strains,I type for 2 strains,J type for 1 strain and L type for 82 strains.Among them,the L-type strains were predominantly circulating in China,and its prevalence rate in this study is as high as 85.4 %.Antibiotics are usually easy to use and have good effects.Therefore,antibiotics are mainly used to control the prevalence of M.synoviae in chickens in China to reduce the economic losses caused by the outbreak.However,due to the long-term overuse of antibiotics in the breeding process,the drug resistance of pathogenic bacteria（mainly including bacteria,Mycoplasma,and Chlamydia）has been continuously generated,which has brought great challenges to the clinical application and infection control of antibiotics in China.In order to make antibiotics play a better clinical role and reduce the production of drug-resistant bacteria,we designed primers for the resistance genes of quinolones and macrolide antibiotics commonly used for the treatment of M.synoviae and screened and amplified the resistance genes of M.synoviae isolated,to guide the clinical identification of drug-resistant strains more conveniently and quickly by molecular diagnostic methods.As the results demonstrated,the single nucleotide site mutation and amino acid substitution of theses isolated strain were similar with the reference strain M.synoviae HN01.At the same time,the experimental results showed that the detection of antibiotic-sensitive types guided by PCR technology could provide a reference for the prevention and control of M.synoviae.