Antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae from Rwanda, 1984–1990

Abstract

A total of 383 clinical isolates of Streptococcus pneumoniae, obtained from an equal number of patients in Kigali, Rwanda, was tested for resistance to penicillin G with a 1 microgram oxacillin disc. Of these isolates, 99 (25.8%) showed reduced zones of inhibition. By means of an agar dilution method, 21% all isolates were confirmed as relatively resistant (MIC > or = 0.12- < or = 1.0 mg/l) strains of Streptococcus pneumoniae (RRSP). A high degree of resistance to penicillin G (MIC > or = 2 mg/l) was not observed. Resistance to chloramphenicol (MIC > or = 8 mg/l) was found in 31% RRSP and in 6% penicillin susceptible strains (PSSP). Doxycycline resistance was common in both RRSP and PSSP strains. All isolates remained fully susceptible to erythromycin. Children more often harboured a strain giving a reduced inhibition zone than did adults (74/230 versus 25/153; P = 0.0005). A total of 32 serotypes or serogroups were identified, seven of them relating to 64.8% all isolates typed. Of all the isolates 84% belonged to a serotype represented in the 23-valent vaccine or to a cross-reacting serotype. Serotype 25, not included in the vaccine, accounted for 10.7% typed isolates from adults but only for 2.0% typed isolates from children. Results of susceptibility testing and clinical experience suggest that penicillin G, ampicillin and chloramphenicol should not be used alone as empirical treatment for pneumococcal meningitis in patients in Rwanda.