CUR - The Council on Undergraduate Research

Antibiotic Resistance in Streptococcus Pyogenes

Ryan Dejam, Kilee Davis, and Dr. Michaela Gazdik Stofer, Department of Biology, Utah Valley University, 800 W University Pkwy, Orem, UT 84058

Group A Streptococcus (GAS) are common bacterial pathogens responsible for a range of bacterial infections from streptococcal pharyngitis to necrotizing fasciitis (NF) . This study focuses on the antibiotic resistance of the bacterial strain Streptococcus pyogenes. S.pyogenes throat samples were collected from a local pediatrics clinic, which prescribes azithromycin, amoxicillin, and amoxicillin/clavulanic acid (Augmentin) as the standard response to Strep infections. S. pyogenes was isolated from throat swab specimens using selective strep agar with 5 percent sheep blood (BBL) and bacitracin disc. In testing for resistance we used the three standard treatment antibiotics in our experimentation. The minimum inhibitory concentration (MIC) was determined for each sample using E-test strips (BioMerieaux). The experimental values were then compared to accepted values from the M100-S25 Performance Standard for Antimicrobial Susceptibility Testing Informational Supplement (CLSI) in order to determine resistance status. This study is a continuation and is ongoing as new samples are procured, with analysis and interpretation complete for over 170 samples. These samples will then be tested for resistance phenotypically and genotypically through sequencing. Thus far, there is resistance shown in 74 samples tested against azithromycin, 80 samples for amoxicillin, and 79 samples for Augmentin. 5.6% of the samples tested resistant against azithromycin, 31% against amoxicillin, and 27% against Augmentin. As this study progresses, it is becoming more clear that resistance is more present than currently assumed by the medical community.

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