Antibiotic susceptibility of pneumococci isolated in Austria over a four-year period

The antibiotic susceptibility of pneumococci isolated from clinical specimens from 1991 through 1994 was investigated. Of 305 strains tested by the agar dilution method, 16 (5.2%) were resistant to penicillin (MICs ≥ 0.12 mg/l). Of the resistant strains, 0.3% showed high-level resistance (MIC ≥ 2 mg/l). The rate of resistance to erythromycin (MIC ≥ 4 mg/l) was 2.3%, to tetracycline (MIC ≥ 8 mg/l) 8.5%, to chloramphenicol (MIC ≥ 8 mg/l) 1.0%, and to trimethoprim sulfamethoxazole (MIC ≥ 3.2/64 mg/l) 3.3%. Penicillin-resistant strains showed significantly higher resistance to the other antibiotics tested. Resistance to penicillin was higher in isolates from the respiratory tract than in those from blood and cerebrospinal fluid (6.2% vs. 2.4%, respectively). There was no increase in penicillin resistance from 1991 through 1994 (5.3% vs. 4.9%, respectively).