Detection of group A Streptococcus: comparison of solid and liquid culture media with and without selective antibiotics.
Eight hundred thirty-seven consecutive throat cultures from pediatric patients were cultured comparatively on conventional sheep blood agar and selective agar containing 1.25 micrograms/ml trimethoprim and 23.75 micrograms/ml sulfamethoxazole. In two sequential studies the sheep blood agar-sulfamethoxazole-trimethoprim plates were significantly (P less than 0.01) more sensitive for Group A Streptococcus (Strep-A) detection than conventional sheep blood agar plates or Todd-Hewitt broth using the fluorescent antibody-antigen detection technique. The selective plates inhibited normal upper respiratory flora but not Strep-A. An incubation time of 18 hours was significantly better than one of 4 hours for the detection of Strep-A antigen in cultures incubated in Todd-Hewitt broth alone or Todd-Hewitt-sulfamethoxazole-trimethoprim broth, resulting in a 24% increase in positives. These studies demonstrate that Strep-A detection in throat swab specimens, by either culture or antigen detection, will be influenced by the use of selective antibiotics and incubation time.
Tolliver
P R
PR
Roe
M H
MH
Todd
J K
JK
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002648:Child; D003470:Culture Media; D005455:Fluorescent Antibody Technique; D006801:Humans; D010614:Pharynx / Q000382:microbiology; D011237:Predictive Value of Tests; D013290:Streptococcal Infections / Q000175:diagnosis*; D013297:Streptococcus pyogenes / Q000302:isolation & purification*
D000900:Anti-Bacterial Agents; D003470:Culture Media