Hathaway, Audrey E. (PhD)Gebreselassie, Solomon2018-07-162023-11-082018-07-162023-11-081996-05http://etd.aau.edu.et/handle/123456789/8811In this study, M. catarrhalis was isolated from 68 of 200 (34.0%) sputum samples of patients with community-acquired pneumonia. It was also found in 56 (28.0%) of the nasopharynx of these patients. There were 42 (61.8%) males. and 26 (38.2%) females with pneumonia caused by M. catarrhalis. Fifty one of the 68 (75.0%) had chronic underlying diseases. Of the isolates from sputum 37 (54.4%) and 32 (57.1%) of the 56 nasopharyngeal isolates were p-Iactamase positive. An ELISA was used to determine the antibody response of sera of patients with pneumonia caused by M. catarrhalis to the outer membrane proteins (OMPs) of the bacterium for both IgG-A-M and IgG31eveis in the sera. It was found that 40 of the 68 (58.8%) patients with pneumonia caused by this organism showed significant rise in the total immunoglobulin (IgG-A-M) level, and 43 of 68 (63.2%) in the IgG3 level in their convalescent sera. In the control sera only I of 30 (3.3%) patients had significant rise for IgG-A-M while none of them showed significant increase in titre for IgG3 (P< 0.05). Using lipopolysaccharide (LPS) antigens, only 16 of 68 (23.5%) paired sera showed significant increase in antibody titre for both IgG-A-M and IgG3 compared to 2 of 30 (6.7%) of controls (P< 0.05). Significant bactericidal activity of the convalescent-phase sera at a dilution of 60% was detected in l3 of 15 (86.7%) of the sera assayed. The same sera without complement were used as controls and none of the controls showed significant bactericidal activities (P< 0.05).enCatarrhalisThesis