Antimicrobial resistance in respiratory tract Streptococcus pneumoniae isolates: results of the Canadian Respiratory Organism Susceptibility Study, 1997 to 2002.
A total of 6,991 unique patient isolates of Streptococcus pneumoniae were collected from October 1997 to June 2002 from 25 medical centers in 9 of the 10 Canadian provinces. Among these isolates, 20.2% were penicillin nonsusceptible, with 14.6% being penicillin intermediate (MIC, 0.12 to 1 microg/ml) and 5.6% being penicillin resistant (MIC, > or =2 microg/ml). The proportion of high-level penicillin-resistant S. pneumoniae isolates increased from 2.4 to 13.8% over the last 3 years of the study, and the proportion of multidrug-resistant S. pneumoniae isolates increased from 2.7 to 8.8% over the 5-year period. Resistant rates (intermediate and resistant) among non-beta-lactam agents were as follows: macrolides, 9.6 to 9.9%; clindamycin, 3.8%; doxycycline, 5.5%; chloramphenicol, 3.9%; and trimethoprim-sulfamethoxazole, 19.0%. Rates of resistance to non-beta-lactam agents were higher among penicillin-resistant strains than among penicillin-susceptible strains. No resistance to vancomycin or linezolid was observed; however, 0.1% intermediate resistance to quinupristin-dalfopristin was observed. The rate of macrolide resistance (intermediate and resistant) increased from 7.9 to 11.1% over the 5 years. For the fluoroquinolones, the order of activity based on the MICs at which 50% of isolates are inhibited (MIC(50)s) and the MIC(90)s was gemifloxacin > clinafloxacin > trovafloxacin > moxifloxacin > grepafloxacin > gatifloxacin > levofloxacin > ciprofloxacin. The investigational compounds ABT-773 (MIC(90), 0.008 microg/ml), ABT-492 (MIC(90), 0.015 microg/ml), GAR-936 (tigecycline; MIC(90), 0.06 microg/ml), and BMS284756 (garenoxacin; MIC(90), 0.06 micro g/ml) displayed excellent activities. Despite decreases in the rates of antibiotic consumption in Canada over the 5-year period, the rates of both high-level penicillin-resistant and multidrug-resistant S. pneumoniae isolates are increasing in Canada.
Zhanel
George G
GG
Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
Palatnick
Lorraine
L
Nichol
Kimberly A
KA
Bellyou
Tracy
T
Low
Don E
DE
Hoban
Daryl J
DJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002170:Canada; D024901:Drug Resistance, Multiple, Bacterial; D004917:Erythromycin / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D024841:Fluoroquinolones; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D048628:Ketolides; D008137:Longitudinal Studies; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D011008:Pneumococcal Infections / Q000382:microbiology*; D015363:Quinolones / Q000494:pharmacology; D012141:Respiratory Tract Infections / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D000078304:Tigecycline; D018440:beta-Lactam Resistance
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D007211:Indoles; D048628:Ketolides; D015363:Quinolones; D004917:Erythromycin; D000078304:Tigecycline; D008911:Minocycline; C405499:cethromycin; C419689:garenoxacin