Comparison of immediate and delayed culture methods for isolation of group A streptococci

Recovery rates of Group A beta-hemolytic streptococci in throat cultures from 300 children were studied using three different methods. The swabs were streaked onto plates immediately, streaked from the same dry swabs held at room temperature for 3 to 6 hours and streaked from swabs held in transport media at room temperature for 3 to 6 hours. The cultures were processed in a pediatric office and interpreted by a microbiologist. The recovery rates were similar for the three methods, but the cultures were easier to interpret when the swabs had been allowed to dry before streaking as a result of a decrease in the normal flora on these plates. In a separate study the recovery of Group A beta-hemolytic streptococci from 187 swabs was identical whether the swabs were streaked at 3 to 6 hours or at 18 to 24 hours.