1564. Surveillance of Macrolide and Clindamycin Resistance in Clinical Isolates of Beta-hemolytic Streptococci in Philadelphia
Session: Poster Abstract Session: Microbial and Host Genetic Factors in Disease
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • betastrep poster IDSA.pdf (2.0 MB)
  • Background:

    Beta-hemolytic streptococci (BHS) cause a variety of infections from pharyngitis to necrotizing fasciitis and neonatal sepsis. Infections with streptococci typically respond to treatment with penicillin (PCN). In patients with PCN allergy, clinicians often use macrolides or clindamycin (CLI) as alternatives. Constitutive and inducible resistance among BHS to macrolides and CLI is increasing globally. Variability in the BHS resistance rates has been reported according to region and serogroups. Despite this trend, susceptibility testing for BHS isolates is not universally done. Thus, we sought to determine the frequency of BHS resistance to erythromycin (ERY) and CLI, including inducible CLI resistance, in the populations served by a community teaching hospital in north Philadelphia. We also explored resistance variation based on age, gender, specimen origin, season, setting of collection, and streptococci serogroups.


    We prospectively enrolled 225 sequential BHS isolates identified by the microbiology laboratory of Einstein Healthcare Network from July 2010 to June 2011. Only one specimen per patient was included. ERY, CLI and inducible CLI resistance were determined using disk diffusion tests according to Clinical and Laboratory Standards Institute guidelines.  The Chi-square test was used to compare difference in resistance rates between groups.


    Seventy-nine isolates (35.1%) were resistant to ERY, 67 isolates (29.8%) were resistant to CLI, and an additional 16 (7.1%) had inducible CLI resistance. Most of the resistant isolates were Group B streptococci (GBS):  87.3% of the ERY-resistant isolates, and 84.7% of the CLI-resistant isolates. Focusing on GBS isolates alone (n = 167), 41.3% were resistant to ERY and 43.1% were resistant to CLI.  Conversely, no Group A streptococci were resistant.  Resistance occurred in other, less common serogroups, but was infrequent compared to GBS. 


    We detected an unexpectedly high rate of macrolide and CLI resistance among clinical BHS isolates at our institution.  When considered along with other local surveys, our study confirms that BHS resistance is rising and varies by region and serogroup.  Thus, for BHS infections, macrolides and CLI are not appropriate empirical alternatives to PCN—local susceptibility testing must be routine.

    Lily Jones, DO, Infectious Diseases and International Medicine, University of South Florida, Tampa, FL, Jody Provencher, MS, Laboratory Medicine, St Luke's Hospital, New York, NY, Sherry Pomerantz, PhD, Albert Einstein Medical Center, Philadelphia, PA and Aaron Kosmin, MD, Infectious Diseases, Albert Einstein Medical Center, Philadelphia, PA


    L. Jones, None

    J. Provencher, None

    S. Pomerantz, None

    A. Kosmin, None

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