Drug Resistance Analysis Of Salmonella From Intensive Meat Duck Farms In Some Regions Of Shandong Province

Duck salmonellosis,also known as duck paratyphoid disease,is a bacterial infectious disease with fast transmission speed and high incidence.It mainly occurred in 1-3week-old ducklings,and was usually endemic with high morbidity and mortality.In recent years,duck salmonellosis had a great impact on duck breeding industry with large-scale intensive breeding gradually increased.To prevent salmonellosis in ducks,a large number of antibiotics are used in the breeding process,which resulted in more and more serious antibiotics resistance in Salmonella.Therefore,to clarify the antibiotics resistance and the distribution of resistance genes in Salmonella isolates during breeding,wich will provide a scientific basis for the antibiotic resistance research of Salmonella and standard clinical selection of antibiotics in duck farms.In this study,43 strains of salmonella isolated from intensive duck farms from cloacal cotton swabs,feed,drinking water,feces,air,soil samples a total of 23 serotypes were tested for drug resistance.The disk diffusion method was used to detect and monitor the sensitivity of 12 commonly antibacterial drugs used.Eleven antimicrobial resistance genes were detected by PCR to obtain the drug resistance profile and the carrying status of resistance genes of salmonella from duck,and to compare and analyze the drug resistance characteristics,distribution and mutation characteristics of resistance genes of salmonella from different sources and serotypes.1.The detection of drug resistance phenotypes and multiple drug resistance in Salmonella isolated ducksThe antibiotic resistance rates of 12 common antibiotics(Amoxicillin,Cefotaxime,Butamicarna,Gentamicin,Doxycycline,Neomycin,Macroscopicin,Lincomycin,Erythromycin,Florfenicol,Ciprofloxacin,Enrofloxacin)were detected by drug-sensitivity test related to 43 insolates.The results showed that 43 strains of duck-derived Salmonella showed different degrees of resistance to 12 antibiotics:the resistance rate to lincomycin and erythromycin was as high as 97.67%,followed by neomycin(62.79%),doxycycline(58.14%),florfenicol(53.49%),spectinomycin(48.84%),amoxicillin(46.51%),gentamicin(44.19%),cefotaxime(37.21%),enrofloxacin(32.56%),ciprofloxacin(25.58%),amikacin(13.95%).The strains resistant to 12 kinds of antibiotics in 7 categories are distributed in 4 serotypes of S.Bovismorbificans,S.Cottbus,S.Amdelnis and S.London;There are more than 10 drug resistance spectrums isolated from cloaca,feces,feed,soil samples.3 Salmonella strains isolated from the air were dual drug resistance.In this study,the drug-resistant phenotypes and drug-resistant genotypes of 43 duck-derived Salmonella strains had different degrees of coincidence rate,among which macrolides and aminoglycosides had the highest coincidence rate(100%).2.Resistance gene detection of Salmonella from ducksPCR was used to detect resistance genes of 43 Salmonella strains from ducks.The results showed that the highest detection rate of resistance genes was flo R(48.84%).tet A(44.19%),CTX and TEM(41.86%),rmt B(6.98%),ere A(4.65%)were detected in varying degrees.SHV detection rate was the lowest 2.33%.CMY and arm A genes were not found.In addition,quinolone resistance determining region genes gyr A and par C were detected,and amino acid comparison was carried out after sequencing.Three amino acid mutation types were secnod for gyr A positive gene,which were Ser¹⁶Phe+Asp²⁰Asn,Ser¹⁶Phe and Asp²⁰Gly.Four amino acid mutation types were screened for par C gene,including 2 types of 35 amino acid site mutation,1 type of 34 amino acid site mutation and 1 type of 11 amino acid site mutation.Isolates obtained from cloacal swabs contained 6 types of sampling possessed the most resistant genes,including CTX(44.44%),ere A(11.11%),flo R(55.56%),rmt B(16.67%),SHV(5.56%),tet(A)(44.44%)and TEM(44.44%).No resistance genes detected in soil.It is suggested that duck's body was an important reservoir of resistance genes and an important source of drug resistance dissemination.A total of 23 serotypes were identified from 43 salmonella strains,among which,S.kottbus was the serotype carrying with the largest number(7 resistant genes)of resistant genes.S.Enteritidis serotype and S.Amounderness serotype of them contained 6 resistance genes.S.bonarne serotype,S.London serotype,S.Nagoya serotype and S.Muenchen serotype contained one resistance gene.