β-Lactamase production and antimicrobial susceptibility pattern of Moraxella catarrhalis isolates: report from Pakistan

ObjectiveTo assess the frequency of β-lactamase production and antimicrobial resistance in Moraxella catarrhalis isolated from clinical specimens in Pakistan.MethodsThis cross sectional study (January to December 2010) was conducted in clinical microbiology laboratory of Aga Khan University Hospital. A total of 97 clinical respiratory specimens growing Moraxella catarrhalis were included. Frequency of β-lactamase production and antimicrobial resistance rates against ampicillin, erythromycin, ciprofloxacin and tetracycline were noted by performing minimum inhibitory concentration (MIC). MICs were calculated as MIC50 and MIC90.Resultsβ-Lactamase production was detected in 84% of isolates, which correlated well with high MIC of ampicillin. Majority of isolates were susceptible to erythromycin (97%) and tetracycline (96%) with MIC90=0.12 mg/L and MIC90=1 mg/L respectively. All isolates were found susceptible to ciprofloxacin (MIC90=0.06 mg/L).ConclusionsResult suggests that empirical use of ampicillin should be discouraged while treating respiratory tract infections. This also emphasizes the importance of continuous surveillance in order to detect emerging resistance in Moraxella isolates.