Antimicrobial Resistance Profile And Integron Analysis Of Campylobacter Spp. Isolates From Chicken In Jiangsu Province

Campylobacter is an important food-borne pathogen worldwide.Poultry is recognized as the reservoir of Campylobacter,many antibiotic-resistance Campylobacter strains were emerging gradually and spreading quickly by the food chain,which threat food safety and human health.The aim of this study was to investigate the epidemiology and the resistance characteristics to antibiotics and disinfectants of chicken-resource Campylobacter.spp in Jiangsu Province,and to discover the function of integrons in mediating the co-resistance to antibiotics and disinfectants.A total of 1022 samples were collected from poultry meat and cloacal swabs from chicken farms,wet markets,and supermarkets in Jiangsu province.Susceptibility of bacteria to 27 antibiotics was determined by the Kirby-Bauer(K-B)method as recommended by the CLSI and the susceptibility of strains to benzalkonium chloride(BC)and cetrimonium bromide(CTAB)was assessed by the agar dilution method,qac genes were detected by the PCR.Results:(1)From the 1022 samples collected,312 were positive for Campylobacter isolates(30.5%)including C.jejuni(228/1022,22.3%)and C.coli(84/1022,8.2%).(2)All isolates performed different degrees of antimicrobial resistance especially resistant to ?-lactam,aminoglycoside,quinolone,sulfonamide and tetracylines,the antibiotics with >80%resistance were cefotaxime,ceftriaxone,norfloxacin,ciprofloxacin,trimethoprim and clindamycin;the antibiotics with >50% resistance were ampicillin,amoxicillin,cephalosporins,kanamycin,tobramycin,ofloxacin,nalidixic acid,enrofloxacin,new compound ming and tetracycline;the strains performed a high sensitivity to imipenem,meropenem,erythromycin,azithromycin,chloramphenicol,fluorine benzene and fosfomycin.(3)The range of MIC values for BC and CTAB were 0.25-64 mg/L and 0.125-1024 mg/L,respectively,only qacEdelta1 was detected(8.8%).Each isolate was assessed for the presence of the int1 and the qacEdelta1 and sul1 genes in the3'-CS and int2 gene to investigate the epidemic of integron,representative isolates were selected for MLST typing.Results:(1)It indicated that 126 strains contained the int1 gene,7 strains contained the int2 gene and 58 strains(40 C.jejuni;18 C.coli)were 3'-CS positive.(2)MLST suggested that strains containing the integrase had widespread distributions in the community,72 strains were belonged to 30 sequence types(STs)and 61 strains were belonged to 33 new allele combinations,ST-1213(6%)and ST-4258(6%)were the most common STs among them;The largest number of alleles was 25 with pgm and tkt,a minumum number of alleles was 18 with uncA;six groups were appeared by the UPGMA(unweighted pair-group method with arithmetic means),Group V with large clusters were obtained from122 strains isolated from geographically distant locations and sources,which including 56 STs.PCR was used to amplify the variable regions of integrons in 58 strains.The DNA of strains which containing cassettes was joint into C.jejuni NCTC11168 by the natural transmission,and the integrase was eliminated by SDS then the strains were tested the change of antimicrobial resistance from phenotype to genotype.Results:(1)Sequence analysis revealed that only 15 strains contained a cassette structure and presented a co-resistance to antibiotics and disinfectants,the variable regions of the class 1integron was aad A1 gene encoding aminoglycoside resistance,including 10 C.jejuni and 5 C.coli.(2)The rate of successful transmission was 40%,the transformed NCTC 11168 could detect the completed integron structure with phenotype change.(3)The gene cassette was eliminated after SDS disposed,the resistance of aminoglycoside drugs was reversed apart from streptomycin and kanamycin.In conclusion,we isolated and identified 312 strains from 1022 samples(30.5%)collected from geographically distant locations and sources from chicken meat and cloacal swabs;most of the strains showed co-resistance to antibiotics and disinfectants;the prevalence of class 1 integron was 18.6% in Campylobacter;The aadA1 gene encoding aminoglycoside resistance was also identified in the gene cassette;the cassettes can not only been transformed horizontally but also been eliminated by chemical method.