Comparison of Dio-Bacit, Bacitracin-Trimethoprim/ Sulphamethoxazole and Latex Agglutination in the Diagnosis of Group A Beta-Hemolytic Streptococci

ABSTRACT

Not only is Group A beta-hemolytic Streptococcus (GAS) the most frequent cause of bacterial pharyngitis, it is also the culprit in various skin and systemic infections, acute rheumatic fever, post streptococcal glomerulonephritis, and other disorders and complications. A new, ready-to-use media, Dio-Bacit, in a two section plate containing 5% sheep blood agar on one side and sheep blood agar with bacitracin (2microgram/ml) on the other was compared for its efficiency in identifying GAS with bacitracin and bacitracin + sulphamethaxazole / trimethoprim disk tests applied after isolation of beta-hemolytic colonies. We also used the latex-agglutination test as the gold standard method for differentiating GAS from streptococci belonging to other groups. Compared with the latex-agglutination test, we found the sensitivity and specificity of the Dio-Bacit method to be 92.0% and 96.9%, respectively. Dio-Bacit plates provide an easy and very useful way to identify GAS within one day, saving time, labor, and money for routine diagnostic microbiology laboratories.