Original Article

Group A Streptococcus: Another Resistant Pathogen

Authors: Robin LaCroix, MD, Anna Kathryn Rye, MD

Abstract

Objectives: In Greenville, South Carolina in 1992, erythromycin resistance in GAS was less than 5%, and there were no fully resistant strains. With a large increase in macrolide and azalide usage within the Greenville area, we again examined susceptibility patterns of pharyngeal GAS isolates in 2002 to 2003.


Methods: Community pediatric offices supplied 106 GAS isolates for study. Screening for macrolide resistance was done via Kirby-Bauer disk diffusion testing. Zones of inhibition from 16 to 20 mm were interpreted as intermediately resistant, and those 15 mm or less were interpreted as resistant per National Committee for Clinical Laboratory Standards guidelines.


Results: A total of 106 GAS isolates were tested; 0.9% of isolates were intermediately resistant to erythromycin and 11% were fully resistant.


Conclusions: The rate of erythromycin resistance among GAS isolates has increased in the past 10 years in the Greenville community. This pattern has paralleled the increased utilization of macrolides in the same community. Continued monitoring of resistance rates will be needed to alert practitioners of possible treatment failures due to macrolide resistance.


Key Points


* Streptococcus pyogenes has increasing resistance to macrolides.


* Use of azalides and macrolides may be a factor in increasing resistance.


* Geographic variations of Streptococcus pyogenes resistance have been well described in the medical literature.

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