CLINICAL AND BACTERIOLOGICAL STUDY OF BRONCHOPULMONARY INFECTIONS CAUSED BY STREPTOCOCCUS PNEUMONIAE

Abstract

Between January 1984 and May 1987, 221 episodes of respiratory infection caused by Streptococcus pneumoniae (S. pneumoniae) were diagnosed in 154 patients by quantitative sputum culture. In 118 (53%) of 221 episodes, S. pneumoniae was isolated in pure culture.In 92 (89%) of the remaining 103 episodes, S. pneumoniae was associated with Haemophilus influenzae (H. influenzae) and (or) Branhamella catarrhalis (B. catarrhalis).A bacterial colony count for S. pneumoniae of more than 10⁷ CFU/ml was found in 105 (89%) of 118 episodes where S. pneumoniae was isolated alone. Ten patients had pneumonia, which was cured in all cases. Fever was present in 29% of the cases in which S. pneumoniae was isolated as a single pathogen, while C-reactive protein was positive in 75% and had a 99% correlation coefficient with the white blood cell count in peripheral blood. S. pneumoniae strains isolated from 1984-1986 were susceptible to ampicillin, of which the minimal inhibitory concentration (MIC) at 90% was less than 0.1μg/ml.
The MICs of minocycline, erythromycin, ofloxacin and norfloxacin ranged from 0.05-50, 0.013 to more than 100, 1.56-3.13 and 6.25-25μEg/ml, respectively. Fourteen per cent of the strains isolated from 1975-1977 were resistant to minocycline while resistance to erythromycin and clindamycin was not detected. Ten years later, however, the occurrence of pneumococci resistant to minocycline, erythromycin and clindamycin was 23%, 7% and 6%, respectively. In the former period, only 1 of 61 tested strains had intermediate resistance to ampicillin, whereas 6 of 67 strains isolated from 1984-1986 presented intermediate resistance. This study demonstrates the usefulness of quantitative culture of homogenized sputum for determining the causative organism (s) of respiratory infections.
Furthermore, according to the in vivo and in vitro results, it supports the notion that penicillins remain the drug of choice in respiratory infections due to S. pneumoniae.