C. Lee, D.E. Low, J. De Azavedo, L. Trpeski, M. Lovgren, G. Tyrrell, B.M. Willey, S. Pong-Porter, A. McGeer. Univ. of Toronto, Toronto, ONT, CANADA; Mount Sinai Hosp., Toronto, ONT, CANADA; Natl. Ctr. for Streptococcus, Edmonton, ALB, CANADA; Ontario Group A Streptococal Study, Toronto, ONT, CANADA.

Background Significant rates of eryR in group A streptococci (GAS) have been reported in several countries, with the emergence of resistance associated increases in erythromycin use.

Methods Population-based surveillance for invasive GAS (illness associated with a sterile site culture positive for S. pyogenes) disease has been performed in Ontario (pop. 11M) since 1992. We tested isolates from surveillance eryR by disk diffusion. Resistance was confirmed using microbroth dilution as per NCCLS. Resistant strains were further analyzed with three-disk method with 1 ery disc (center) and 2 clindamycin (C) discs on each side to detect inducible MLS phenotype. M, T typing and PFGE using Smal were performed. Macrolide usage data was obtained from IMS Canada.

Results There has been a significant increase in eryR (p<.001). The majority of increase is due to the introduction of M-nontypeable strains first identified in 1995. These strains accounted for 0/ 5 eryR in 1992/3, 2/6 eryR in 1995, 14/22 in 1997/8 (P=0.03). Of the 33 eryR strains, 78.8% (26) were sensitive to C, but 33.3% (11) showed inducible resistance to C.

Conclusions Despite a decade of stability in macrolide use, there has been a significant increase in ery R associated with the introduction of new GAS strains.

Presented at: