Susceptibility of beta-hemolytic streptococci to nine antimicrobial agents among four medical centers in Salt Lake City, Utah, USA.

A multicenter study was performed to evaluate the susceptibility of beta-hemolytic streptococci to nine antimicrobial agents. MICs were performed in cation-supplemented Mueller-Hinton broth with 3.5% lysed sheep red blood cells according to NCCLS guidelines. A total of 646 isolates were tested: 300 (46%) group A; 170 (26%) group B; 38 (6%) group C, 35 (5%) group F; 83 (17%) group G; and 20 (3%) nongroupable. Six percent of the total isolates were resistant to one or more of the antibiotics tested. Approximately 7% of 387 strains from the University of Utah Hospital and Clinics were resistant to erythromycin. Four isolates were resistant to clindamycin. Six strains (3%) from Primary Children's Medical Center (207 tested) were resistant to one or more of the macrolides. Resistance was rare at the LDS Hospital and the Salt Lake Veteran's Affairs Hospital. Overall, resistance among beta-hemolytic streptococci in this geographic location does not seem to be a significant problem, except at the tertiary care university hospital.