Primary plate identification of group A beta-hemolytic streptococci utilizing a two-disk technique

Area of Science:

• Clinical Microbiology
• Diagnostic Bacteriology

Background:

• Group A beta-hemolytic streptococci (GABHS) are a common cause of bacterial pharyngitis.
• Accurate and rapid identification of GABHS is crucial for timely treatment and preventing complications.

Purpose of the Study:

• To evaluate a novel two-disk system for the primary plate identification of GABHS in throat cultures.
• To assess the efficiency and cost-effectiveness of this method compared to standard techniques.

Main Methods:

• A two-disk system utilizing trimethoprim-sulfamethoxazole and bacitracin disks was applied to primary throat culture plates.
• Throat specimens (n=259) were processed, and results were compared to broth incubation with fluorescent antibody staining as a control.

Main Results:

• The two-disk system allowed visualization of GABHS by inhibiting normal flora.
• 75% of positive cultures were unequivocally identified after overnight incubation; 25% required subculture.
• The method achieved 91% recovery of true positive cultures compared to the control method.

Conclusions:

• The two-disk system offers a significant time-saving advantage over standard plate methods.
• This technique provides a cost-effective alternative to broth-fluorescent-antibody methods, especially in resource-limited laboratories.
• It is particularly valuable for rapid GABHS detection in clinical settings.