Evolving patterns of resistance to respiratory pathogens in Canada.

Active surveillance of changing resistance patterns is difficult but important for rational therapeutic choices. In Canada, penicillin resistance in Streptococcus pneumoniae has evolved more slowly than in other countries (in Europe and Israel rates exceed 50%). Currently, penicillin resistance is found in roughly 21% of Canadian isolates, and cross-resistance is becoming common. Beta-lactamase production is now found in approximately 28% of Haemophilus influenzae isolates, although more recently, rates over 30% have been found in some areas of Canada. In Moraxella catarrhalis, beta-lactamases are produced by 80% to 90% of bacteria, with resistance to trimethoprim/sulphamethoxazole also found. To date, there have been only a few reports of resistance to the fluoroquinolones. The apparent increase in the rate of development of resistance and cross-resistance will lead to new therapeutic challenges.