Antibiotics Resistance and bro Genotyping in Moraxella Catarrhalis Isolates Carried by Children

Objective To determine the beta-lactamase producing rate and susceptibility of nine antibiotics of 214 Moraxella Catarrhalis isolates carried by children and to investigate the characteristics of beta-lactamase resistant gene. Methods British Society for Antimicrobial Chemotherapy (BSAC) disk diffusion test and agar dilution test were taken to determine minimal inhibition concentration (MIC) and antibiotic resistance of Mc strains Nitrocefin disk test was used to detect beta-lactamase producing. PCR combining restriction endonuclease analysis was employed to do the bro genotyping. Results Among 214 strains, 94. 4% of them produced the beta-lactamase. The beta-lactamase producing isolates had the MIC90 32 mg/L for ampicillin, 2 mg/L for cefuroxime, and 8 mg/L for cefaclor, which were higher than the non beta-lactamase producing isolates 0. 5 mg/L, 1.0 mg/L and 0 5 mg/L respectively The resistant rates of beta-lactamase producing isolates were 95% for ampicillin, 46. 5% for cefuroxime, and 76 2% for cefaclor, which were also higher than non beta-lactamase producing isolates (0). There was no significant difference between beta-lactamase producing isolates and non beta-lactamase producing isolates in the susceptibility for cefotaxime, erythromycine, ciprofloxacin, tetracycline and chloramphenicol, with total susceptibility rates of 100% , 95 8% , 100% , 34.1 % and 100% , respectively. All of the isolates in this study were resistant to cotrimoxazole. 69.8% (141/202) of beta-lactamase producing isolates had bro-Ⅰ and 30. 2% (61/202) bro Ⅱ The isolates carrying gene of bro-Ⅰ had higher MIC50 and MIC90 than bro- Ⅱ strains. Conclusions There is high prevalence of beta-lactamase producing Moraxella Catarrhalis in Beijing children. Those isolates have high resistant rates to ampicillin. The dominant genotype for beta-lactamase producing isolates is bro-Ⅰ. The isolates carrying bro-Ⅰ gene are strongly resistant to beta-lactamase antibiotics than that carrying bro- Ⅱ gene.