Antimicrobial resistance and BRO genotyping of Moraxella catarrhalis isolates from respiratory tract in children

Objectives To investigate antimicrobial resistance and beta-lactamase production of Moraxella catarrhalis isolates from respiratory tract in children and to understand the characteristics of BRO beta-lactamase gene.Methods From June 2011 to September 2012,401 Moraxella catarrhalis isolates were obtained from respiratory tract in children.Minimum inhibitory concentrations(MIC) of commonly-used antibiotics were determined by microbroth dilution assay,and beta-lactamase production was detected by Nitrocefin disk test.PCR combining restriction endonuclease analysis was employed to do the BRO genotyping.Results 96.5% isolates were beta-lactamase positive(387/401),MIC(MIC50/MIC90) values and resistant rates of beta-lactamase producing isolates were higher than those of non beta-lactamase producing isolates for ampicillin,cefaclor and cefuroxime(P0.05).The positive rate of BRO gene was 99.2% in beta-lactamase producing isolates(384/387),consisting of 93.0% BRO-1 isolates and 7.0% BRO-2 isolates.MIC50 and MIC90 values of BRO-1+isolates were higher than those of BRO-2+isolates for ampicillin,cefaclor,cefuroxime and azithromycin.Conclusions The beta-lactamase production rate is high in Moraxella catarrhalis isolates from respiratory tract in children.BRO1 type was the dominant genotype of beta-lactamase producing isolates,having more influence than BRO-2 type in the influence on some beta-lactams and macrolides.