[Resistance to erythromycin in Streptococcus pneumoniae].

A total of 640 S. pneumoniae isolates from different clinical samples obtained from patients (not including carriers) over a 10 years period were studied. Global resistance to erythromycin (MIC greater than or equal to 1 microgram/ml) was 9.1% (8.1% with MIC greater than or equal to 8 micrograms/ml). Resistance was more prevalent in serotypes 6, 14, and 19, either in absolute number or in relation to the total number of strains in each serotype. A total of 16% of strains isolated from ear fluid specimens and bronchial secretions were resistant, but only a 4.5% of blood culture isolates showed also resistance to erythromycin. Resistance was found more frequently on pediatric patients. Although the highest resistance rate was found during the last year (15% of all 1990 isolated strains or 13.9% if the period also includes the first 1991 quarter) we did not find a gradual increase over time. Most of the resistant strains showed also resistance to tetracycline and other antimicrobial agents. Overall, 94.8% of strains showed multiple resistance (combined resistance to at least 2 other different antibiotics, not including clindamycin resistance, which always matches erythromycin resistance), and 60.3% showed resistance to penicillin. The multiply-resistant pattern and the similarity of isolated strains suggest an epidemiologic behaviour that not necessarily has to be linked to higher erythromycin use.