Зображення 01295. Streptococcal culture on a Petri dish

Culture on a Petri dish is the most sensitive method to detect haemolytic streptococci in a throat sample. Group A haemolytic streptococci leave a zone of inhibited growth around a bacitracin disk (upper picture), while other haemolytic streptococci (usually group C or G) do not leave such a zone (lower picture).