University Archives

Moraxella catarrhalis is a gram-negative coccus that can cause bronchopneumonia in patients that are elderly and heavy smokers suffering with chronic obstructive pulmonary disease (COPD). This study isolated and characterized spontaneous rifampicin resistant mutants of M. catarrhalis. It grows well on rich media such as sheep blood agar and brain heart infusion (BHI) agar at body temperature. Rifampicin stops cell function by making a complex with DNA - dependent RNA polymerase. Rifampicin resistant colonies would grow on BHI agar containing rifampicin after several days of incubation. Streak plate purified mutant strains would grow on BHI agar containing rifampicin in contrast to the wild type strain. With the disc diffusion method of assessing antibiotic susceptibility, rifampicin inhibition zone diameters for the mutants ranged from 0 to 19 mm in contrast to the zone diameter for the wild type strain that was about 33 mm. The mutants did not show any considerable change in inhibition zone diameters for several other antibiotics. With the GEN III MicroPlate redox-based array (Biolog Inc.) a positive reaction was exhibited for rifampicin resistance by mutants. This array consisted of 71 carbon source utilization assays and 23 chemical sensitivity assays in a 96 – well microplate. Other array test results for mutants appeared similar to the those for the wild type strain. The reaction profile also showed that mutant strains and wild type were related. The mutants should be valuable for further study of M. catarrhalis.