Sensitivity to penicillin of S. pneumoniae strains isolated from various pathological conditions.

297 S. pneumoniae strains isolated from patients with different pneumococcal infections during 1990-1991 were tested for the sensitivity to antibiotics--by the diffusimetric method to 9 antibiotics (Penicillin (6 micrograms), Ampicillin (10 micrograms), Erythromycin (15 micrograms), Oxacyllin (5 micrograms), Streptomycin (50 micrograms), Tetracycline (50 micrograms), Chloramphenicol (50 micrograms), Rifampicin (6 micrograms), and Kanamycin (30 micrograms) and by MIC determination to Penicillin and Erythromycin. 30% of S. pneumoniae strains were resistant to Penicillin and Erythromycin corresponding to a MIC > or = 1 UP/ml or > or = 1 microgram E/ml. The most active antibiotics were Chloramphenicol and Rifampicin and the less active: Tetracycline, Kanamycin and Streptomycin. A relation between the origin and serotype of the strains and the sensitivity to antibiotics was revealed. The strains from the throat, conjunctive and otic secretions and belonging to serotypes 19, 6 and 14 showed the highest levels of resistance to all antibiotics. A good correlation between MIC and diffusion method results was observed to Erythromycin and no correlation to Penicillin. In this last case the results of MIC determination to Penicillin were better correlated with the results of inhibitions diameters to Oxacyllin, method which have to be recommended.