Publications
Increasing
Prevalence of Macrolide Resistance (MR) in Community Acquired Pharyngeal
Isolates of Group a Streptococci (GAS) from Ontario, Canada. K.
C. KATZ1,2, A. J. MCGEER1,2, C. L. DUNCAN1,
B. M. WILLEY1, A. SARABIA3, J. MCCANN3,
S. PONG-PORTER1, Y. RZAYEV1, J. S. DE AZAVEDO1,2,
D. E. LOW1,2; 1Toronto Medical Laboratories/Mount
Sinai Hospital Department of Microbiology, Toronto, ON, Canada, 2University
of Toronto, Toronto, ON, Canada, 3MDS Laboratories, Toronto,
ON, Canada.
Background:
The prevalence of MR in GAS is geographically variable. In North
America, although isolated pockets of MR have been reported, the
prevalence has remained ~2%. In 1997, the GAS MR rate was 2.1% (67/3205
isolates) in Ontario. The current study aims to assess evolving
trends in GAS MR in community isolates.
Methods:
A private lab serving community physicians in southern Ontario (popn.
Base 5M) collected 500 consecutive GAS isolates from throat swabs
in 2001. EryR strains were identified by disk diffusion using NCCLS
guidelines . To distinguish between M and MLSB a two
disk test was performed. MICs of erythromycin, clindamycin, ABT
773, telithromycin, and spiramycin (as well as others) were determined
for EryR strains using broth microdilution. PCR was performed for
mef and erm genes. Results were compared to those
fromGAS isolates from the same lab in 1997.
Results:
72 of 500 (14.4%) isolates tested were MR by disk diffusion and
broth microdilution. 66 (92%) were M phenotype and 6 (8.3%) were
MLSB phenotype. Of the MLSB resistant strains,
4/6 demonstrated blunting of the clindamycin inhibition zone indicating
inducible resistance. All (62/62) of the M phenotype isolates tested
possessed the mefA gene. Ery MICs ranged from 0.06 to >32
µg/ml. No strains were resistant to ciprofloxacin,
levofloxacin, penicillin, vancomycin, or linezolid. Three isolates
were resistant to tetracycline. Two isolates had telithromycin MIC
>1. Compared with 1997 when the eryR rate in GAS was noted to be
2.1% (67/3205), there has been a significant increase in eryR GAS
isolates, p<0.0001.
Conclusion:
EryR in GAS is rapidly emerging in Ontario, Canada where rates were
previously very low.
42nd INTERSCIENCE CONFERENCE ON ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
(ICAAC), San Diego, California, USA, September 30, 2002. 10:00am-11:30am
©Copyright 2002 Last Modified
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