Antimicrobial resistance among clinical isolates of Streptococcus pneumoniae in Canada during 2000

A total of 2,245 clinical isolates of Streptococcus pneumoniae were collected from 63 microbiology laboratories from across Canada during 2000 and characterized at a central laboratory. Of these isolates, 12.4% were not susceptible to penicillin (penicillin MIC, greater than or equal to0.12 mug/ml) and 5.8% were resistant (MIC, greater than or equal to2 mug/ml). Resistance rates among non-beta-lactam agents were the following: macrolides, 11.1%; clindamycin, 5.7%; chloramphenicol, 2.2%; levofloxacin, 0.9%; gatifloxacin, 0.8%; moxifloxacin, 0.4%; and trimethoprim-sulfamethoxazole, 11.3%. The MICs at which 90% of the isolates were inhibited (MIC(90)s) of the fluoroquinolones were the following: gemifloxacin, 0.03 mug/ml; BMS-284756, 0.06 mug/ml; moxifloxacin, 0.12 mug/ml; gatifloxacin, 0.25 mug/ml; levofloxacin, 1 mug/ml; and ciprofloxacin, 1 mug/ml. Of 578 isolates from the lower respiratory tract, 21 (3.6%) were inhibited at ciprofloxacin MICs of greater than or equal to4 mug/ml. None of the 768 isolates from children were inhibited at ciprofloxacin MICs of greater than or equal to4 mug/ml, compared to 3 of 731 (0.6%) from those ages 15 to 64 (all of these >60 years old), and 27 of 707 (3.8%) from those over 65. The MIC(90)s for ABT-773 and telithromycin were 0.015 mug/ml for macrolide-susceptible isolates and 0.12 and 0.5 mug/ml, respectively, for macrolide-resistant isolates. The MIC of linezolid was less than or equal to2 mug/ml for all isolates. Many of the new antimicrobial agents tested in this study appear to have potential for the treatment of multidrug-resistant strains of pneumococci.