What is the most common bacterial cause of pharyngitis that responds to bacitracin?

The most common bacterial cause of pharyngitis that responds to bacitracin is Streptococcus pyogenes, commonly known as Group A Streptococcus (GAS). This organism is well-recognized as a leading cause of pharyngitis, particularly in children and adolescents.

S. pyogenes is sensitive to bacitracin, which is a critical point because bacitracin sensitivity can be employed in the clinical setting to help differentiate it from other organisms that cause throat infections. When a rapid antigen detection test or throat culture is performed, if the bacteria present are susceptible to bacitracin, it typically indicates S. pyogenes as the causative agent.

The other organisms listed are associated with various clinical presentations but do not respond to bacitracin. Streptococcus viridans is part of the normal flora of the upper respiratory tract and is more associated with dental infections or endocarditis. Haemophilus influenzae can cause respiratory infections but is less common as a primary cause of pharyngitis and has different treatment considerations. Neisseria gonorrhoeae causes gonococcal pharyngitis, which also has distinct clinical features and does not respond to bacitracin.

Understanding the specific characteristics of S.