Identification and in vitro antimicrobial susceptibility of Brucella species / 中华传染病杂志

ABSTRACT

Objective To identify Brucella species by means of bacteriological and polymerase chain reaction(PCR)methods,and to understand the drug susceptibility by in vitro susceptibility test of these strains to eight antimicrobial drugs.Methods The isolated Brucella strains were identified by standard method with conventional positive serum experiment,monophase specificity serum(A,M and R) agglutination experiment and brucella phage splitting experiment(Tb and BK2).Reference strains were set as control group.Molecular typing was performed by polymerase chain reaction(PCR)targeting Brucella surface protein 31(BCSP-31)and(abortus melitensis ovis suis,AMOS)-PCR assay which is able to distinguish among B.abortus,B.melitensis,B.ovis and B.porcine.Microdilution broth method was used to determine the minimum inhibitory concentrations(MIC)of 8 antibiotics to 27 Brucella strains isolated from blood culture,including azithromucin,ciprofloxacin,levofloxacin,doxycycline,rifampicin, gentamicin,acheomycin,and streptomycin.Results Twenty-seven strains were identified as B. melitensis,of which 21 were B.melitensis biovar 3 isolates,6 were B.melitensis biovar 1.The BCSP-31-PCR confirmed that all 27 isolates were Brucella.spp.AMOS-PCR assay confirmed that all isolates were B.melitensis.All isolates were susceptible to ciprofloxacin,levofloxacin,doxycycline,gentamicin, acheomycin,and streptomycin.Doxycycline was the most effective antibiotic(MIC900.064 mg/L),while rifampicin was moderately active to 3 isolates(MIC 2 mg/L).Conclusions Brucella isolates are susceptible in vitro to the antibiotics recommended by world health organization.Regular evaluation of antibiotic susceptibilities of Brucella strains is helpful for epidemiological investigation and antibiotic resistance monitor.