Antibiotic susceptibility of Streptococcus pneumoniae strains isolated from respiratory tract

The antimicrobial susceptibility of 200 Streptococcus pneumoniae strains isolated from nasal swabs, sputum and bronchial aspirate during 1998 and 1999 was determined. Decreased susceptibility to penicillin was detected in 47 (23.5%) strains. Most of them (20%) had MICs of penicillin of 0.1-1 mug/ml and were thus intermediate, while only 6 isolates (3.5%) expressed resistance to penicillin (MICs >1 mug/ml). The resistance to erythromycin, clindamycin, cotrimoxazole and tetracycline was 17%, 20.5%, 60.5% and 16.5% respectively. All isolates were susceptible to rifampin and vancomycin. Our results confirm the existence of isolates of S. pneumoniae with decreased susceptibility to penicillin and other antibiotics and indicate the need to perform susceptibility test for every isolated strain in order to determine the best therapeutic options.