Genetic commonality of macrolide-resistant group A beta hemolytic streptococcus pharyngeal strains.
BACKGROUND
Group A beta hemolytic streptococcus (GABHS) pharyngitis is a common childhood illness. Penicillin remains the gold standard therapy, but macrolides are indicated for the penicillin allergic patient, and are often used for convenience.


METHODS
We conducted a surveillance study of children with pharyngitis and positive streptococcal rapid antigen testing from 10/05 to 10/06 at 2 sites (A & B). Demographics, treatment, and resistance data was collected and compared to previous data from 2002. Erythromycin (EM) resistance was determined by disk diffusion and E-test on 500 isolates. Pulse field gel electrophoresis (PFGE) was performed to measure genetic relatedness of isolates. StatXact version 8 software (Cytel Inc., Cambridge, MA) was utilized to perform Fisher's exact test and exact confidence interval (CI) analysis.


RESULTS
There were no differences in resistance rates or demographic features, with the exception of race, between sites A & B. EM resistance was 0 in 2002, 3.5% in 2005-06 at site A, and 4.5% in 2005-06 at site B. 3/7 and 3/9 had inducible resistance at A and B respectively. 8 isolates had relatedness > or =80%, 5 of which were 88% homologous on PFGE.


CONCLUSIONS
Community macrolide resistance has increased following increased macrolide use. These results may have treatment implications if use continues to be high.
Myers
Angela L
AL
Children's Mercy Hospitals and Clinics, University of Missouri-Kansas City School of Medicine, KC, MO, USA. amyers@cmh.edu
Jackson
Mary Anne
MA
Selvarangan
Rangaraj
R
Goering
Richard V
RV
Harrison
Christopher
C
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002648:Child; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests; D010612:Pharyngitis / Q000382:microbiology*; D011446:Prospective Studies; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D018942:Macrolides