Mechanisms of resistance for Streptococcus pyogenes in northern Utah.
OBJECTIVE
The purpose of this study was to (1) determine the rates of penicillin and erythromycin resistance among Streptococcus pyogenes isolates in northern Utah, and (2) determine the genotype of the erythromycin resistant strains, thereby providing information regarding the mechanism of the resistance.


METHODS
Seven hundred thirty-nine isolates of S. pyogenes were identified on 5% Sheep Blood Agar. Susceptibility to erythromycin and penicillin was performed using Muller-Hinton blood agar. All isolates resistant to erythromycin were then genotyped using PCR primers specific to one of the following: mefA gene, indicating the mechanism of resistance was an efflux pump; ermA gene, in which the mechanism was inducible methylation of the ribosomes; and ermB indicating constitutive methylation of the ribosomes.


METHODS
This study was conducted at Weber State University, in the Department of Clinical Laboratory Sciences.


METHODS
Samples were collected from 9 clinics ranging from North Ogden to Taylorsville, Utah. All samples were previously tested positive for S. pyogenes by the clinic from where the samples were collected.


RESULTS
Of the 739 S. pyogenes isolates tested, 2.4% were resistant to erythromycin with no resistance observed to penicillin. Of the strains that displayed some degree of resistance, the gene frequencies observed were as follows: 48.1% mefA, 26.0% ermA, 3.7% ermB, and 22.2% multiple genes.


CONCLUSIONS
The most common genotype was mefA, indicating that the efflux pump (M phenotype) is the most common mechanism in the surveyed area, followed by ermA, which produces the inducible methylating enzyme. A significant number of isolates was also observed to express both the efflux pump and the constitutive methylating enzyme.
Clinical Laboratory Science Program, Department of Health Professions, Weber State University, Ogden, UT 84408-3905, USA.
Ryan A
RA
Rowe
Ryan M
RM
Stephenson
Destry L
DL
East
Scott
S
Wright
D000554:Ambulatory Care Facilities; D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance / Q000235:genetics*; D010406:Penicillins / Q000494:pharmacology; D010641:Phenotype; D016133:Polymerase Chain Reaction; D013290:Streptococcal Infections / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D014589:Utah
D001426:Bacterial Proteins; C117866:MefA protein, Streptococcus; D008565:Membrane Proteins; D010406:Penicillins; D004917:Erythromycin; D008780:Methyltransferases; C431709:ErmA protein, Bacteria