Serotypes and antibiotic susceptibilities of Streptococcus pneumoniae in Nairobi, Kenya

Two hundred and sixteen clinically significant isolates of Streptococcus pneumoniae from 138 adult patients attending clinics in Nairobi, Kenya over a 2 year period were characterized by antibiotic sensitivity testing and serotyping. Overall antibiotic resistance rates were: penicillin, 25%; tetracycline, 34%; erythromycin, 0%; chloramphenicol, 0.4%. Minimum inhibitory concentrations (MIC's) of penicillin ranged from < 0.008-0.5 microgram/ml. Determination of penicillin resistance (MIC > or = 0.1 microgram/ml) by oxacillin 1 microgram disc diffusion zone diameter < or = 20 mm was 100% sensitive, 92% specific. Relative resistance to oxacillin (MIC range 0.25-1.0 microgram/ml) accounted for penicillin sensitive isolates determined falsely to be penicillin resistant by oxacillin disc testing. Penicillin resistance was more frequent in sputum isolates at 35% than in blood isolates at 18% (P = 0.013). Serotypes 6, 10, 14, 16, 19 and 23 were associated with penicillin resistance. This study provides information of value for planning management strategies for pneumococcal disease from an area where there are few existing data.