Isolation,Identification and Drug Resistance Analysis of Riemerella anatipestifer from Some Areas in Guangdong
[Objective]The experiment was aimed to understand the prevalence of Riemerella anatipestifer(RA),drug resistance and drug resistance gene carrier in some areas of Guangdong province.[Method]In this study,101 liver,heart,brain and other tissues suspected to be infected with RA were collected from Guangdong during 2020-2022.Bacteria were isolated from the collected tissues,and the isolates were identified by Gram staining,biochemical experiments and PCR.The serotype of isolates identified as RA was identified,and K-B disk diffusion method and PCR were used to conduct drug sensitivity tests and corresponding drug resistance gene detection for isolates.Statistical software SPSS 22.0 was used to analyze the drug-resistant phenotypes and drug-resistant genotypes of these strains.[Result]The small round,slightly protruding,shiny and creamy colonies of the isolated bacteria were found in the plate culture containing 5％newborn bovine serum TSA.Gram-stained microscopic examination showed that they were negative short bacilli.The results of biochemical identification showed that the isolates did not ferment carbohydrates,and were positive for oxidase,negative for nitrate reduction,Simon's citrate,peptone water,MR,VP,H2S,and some strains could liquify gelatin and produce urease.The ompA gene was identified by PCR,and 51 strains of RA were isolated in this experiment.Serotype identification of the isolates showed that 5 serotypes were detected,which were serotypes 1,2,4,11 and 18,respectively.Analysis of serotypes of isolates from different host sources showed that serotype 18 was detected only in geese.The results of drug sensitivity test showed that RA was sensitive to flufenicol,ofloxacin,doxycycline,daguamycin,ceftiofurme and cephradine among the 25 drugs selected.The resistance of RA to β-lactam and aminoglycoside was the most serious,among which the resistance rate of β-lactam and aminoglycoside were above 50.0％and 80.0％,respectively.The results of multi-drug resistance showed that the strains with three or more drug resistance were up to 96.08％.Analysis of drug resistance of different host sources showed that the resistance rate of RA isolates from geese to penicillin,amoxicillin,ampicillin and cefazoline was higher than that from ducks.There was no significant difference between duck and goose sources of other drugs.Fifteen drug resistance genes were tested,among which the detection rates of blaCTX-M,aph(3')Ⅱ a,qnrB,qnrS,floR,tetM and ermF genes were relatively high,with detection rates of 70.59％,68.63％,76.47％,96.08％,88.24％,82.35％and 96.08％,respectively.The correlation analysis of drug resistance phenotype and drug resistance gene showed that the drug resistance gene aph(3')Ⅱ a was significantly associated with the development of neomycin and streptomycin resistant strains(P＜0.05),and the drug resistance gene ermF was significantly associated with the emergence of azithromycin-resistant strains(P＜0.05).The drug resistance gene tetX was significantly associated with the generation of doxycycline resistant strains(P＜0.05).[Conclusion]In this study,51 isolates of RA were successfully isolated,and the isolates were resistant to multiple drugs,and the phenomenon of multiple drug resistance was serious.The results of this experiment could provide reference for guiding the formulation of clinical treatment of RA infection in Guangdong province.
Riemerella anatipestiferisolation and identificationdrug resistancedrug resistance gene
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