Investigation On Drug Resistance Of Campylobacter In Tianjin And Qinghai And Its Molecular Resistance Mechanism

Campylobacter is a common foodborne intestinal pathogen.Infection by Campylobacter often causes enteritis with symptoms such as diarrhea,fever,and abdominal cramps;it can also cause complications such as reactive arthritis,bacteremia,and meningitis.In recent years,antibiotics have been widely used in animal husbandry,resulting in the continuous improvement of drug resistance of Campylobacter.If Campylobacter has acquired resistance to clinically key antibiotics,it is likely to lead to a reduction in the number of drugs used in clinically treated patients.And even the treatment failed.In 2017,200 pig anal swabs and 150 chicken cecums were collected from a farm in Tianjin.In August 2018,60 chicken cecums and 55 chicken samples were collected from a farm in Qinghai.A total of 465 samples were collected from the two regions,and 109 strains of Campylobacter were isolated,with a separation rate of 23.4% and among which including Campylobacter coli of 73.4%(80/109),Campylobacter jejuni of 26.6%(29/109).In 265 chicken samples,the rate of Campylobacter isolation was 35%(93 strains);in 200 pig samples,the isolate rate of Campylobacter was 8%(16 strains).The susceptibility test of 109 strains of Campylobacter isolated was carried out.It was found that the resistance rates of Campylobacter jejuni and Campylobacter coli to nalidixic acid and ciprofloxacin were relatively high in Tianjin and Qinghai.The resistance rate of tetracycline in Tianjin and Qinghai was the highest,up to 99%,and the resistance rate of Campylobacter jejuni and Campylobacter coli to tetracycline was consistent.The resistance rates of Campylobacter jejuni and Campylobacter coli to azithromycin,erythromycin,gentamicin and clindamycin were different in Tianjin and Qinghai.The resistance rates of Campylobacter jejuni to azithromycin,erythromycin,gentamicin and clindamycin were 12.5% ? ?(1/8),12.5%? ?(1/8),62.5%(5/8)and 25%(2/8)respectively;the resistance rates of Campylobacter coli to azithromycin,erythromycin,gentamicin and clindamycin were 93.3%(56/60),93.3%(56/60),76.7%(46/60)and 90%(54/60)respectively;the above results showed that the resistance rate of Campylobacter coli to azithromycin,erythromycin,gentamicin and clindamycin in Tianjin is higher than that of jejunal curvature bacteria.The resistance rates of Campylobacter jejuni to azithromycin,erythromycin,gentamicin and clindamycin in Qinghai were 33.3%(7/21),33.3%(7/21)and 57.1%(12/21)and 5%(1/21)respectively;the resistance rate of Campylobacter coli to azithromycin,erythromycin,gentamicin and clindamycin were 5%(1/20),5%(1/20),25%(5/20)and 5%(1/20)respectively;the resistance rate of Campylobacter jejuni to azithromycin,erythromycin,gentamicin and clindamycin was higher than that of Campylobacter coli.The multi-drug resistance rate of isolated Campylobacter in Tianjin was higher than that in Qinghai,and the multi-drug resistance rate was 92.6%,while the multi-drug resistance rate in Qinghai was 41.5%.The results of the gyr A gene in this study showed that 107 strains of Campylobactercontained the gyr A gene,107 strains of Campylobacter contained the gyr B gene,and no Campylobacter contained the par C gene.All of the 107 Campylobacter strains contained the Thr-86-Ile site mutation of the gyr A gene,and no other missense mutations existed.There are multiple point mutations on the gyr B gene,but all of them are synonymous mutations,and do not change the sequence of amino acids.The results of 23 S r RNA gene A2074 and A2075 of macrolide-resistant Campylobacter showed that 47 strains of Campylobacter contained A2075 G mutation,and all macrolide-resistant Campylobacter did not contain A2074 C mutation.Therefore,the A2075 G mutation in the 23 S r RNA gene is the main resistance mechanism of macrolide-resistant Campylobacter.The genes of L4 and L22 in the nucleoprotein large subunit were detected by PCR without mutation.The macrolide antibiotic-resistant Campylobacter has 20 strains containing the erm B gene,and 20 strains of Campylobacter containing the erm B gene are multi-drug resistant.A total of 63 strains of Campylobacter resistant to aminoglycoside antibiotics were detected by PCR.A total of 26 strains of Campylobacter contained aad E-sat4-aph A-3 resistance gene cluster.The results of RFLP typing of 65 strains of Campylobacter resistant strains indicated that Campylobacter had a high degree of genetic diversity.The parental relationship between Campylobacter strains in different regions is different,and the isolated Campylobacter in Tianjin is more close comparison with Campylobacter isolates in Qinghai.The results of MLST typing on 35 strains of Campylobacter showed that the prevalence of Campylobacter in different regions was different,and 19 strains were not found belonging to any existing sequence type(ST)in the database,which might be new ST.The ST of the remaining 16 strains are mainly ST825,ST354 and ST860,of which ST825 and ST860 are the main type in Tianjin region and ST354 is the main type in Qinghai region.