to the editor: The article¹ by Vincent and colleagues in American Family Physician reviews a topic that is highly relevant to my everyday practice in primary care: pharyngitis. Thank you for articles on such topics. I would like to ask the authors if they have any information on the need or validity of offering antibiotic treatment to patients whose throat cultures reveal groups of streptococci other than A? My laboratory routinely evaluates for groups C and G, and there is some literature^2–5 that suggests that treating these groups of patients may be clinically beneficial. However, I am loath to extend the use of antibiotics further in an era of significant rates of microbial resistance and physician tendency to offer treatments without good evidence of efficacy.

in reply: I would like to thank Dr. Mosby for a most intriguing question. Groups C and G beta-hemolytic streptococci certainly have caused well-documented epidemics of acute pharyngitis. These outbreaks often have been associated with contaminated foods (group C with milk-borne outbreaks and group G with infected egg salad and chicken salad). Groups C and G streptococci also are frequently isolated from asymptomatic persons. Groups C and G streptococci express the virulence factor, M protein.⁶ It is difficult to differentiate between colonization and infection. The benefit of antimicrobial therapy has not been established. One author advises that patients with streptococci C and G be treated solely for symptomatic relief.⁷ Others state that there is no proven benefit in treating any pharyngitides other than group A beta-hemolytic strep, Corynebacterium diphtheriae, and Neisseria gonorrhoeae.^8,9 It would appear that we do not understand the pathogenic burden of these organisms, although it is known that the more virulent strains express a C5a peptidase enzyme similar to group A beta-hemolytic strep.¹⁰ My conclusion is that local strain virulence results in the different clinical pathogenic presentations of the organisms under question. The answer: we don’t know if groups C and G streptococci deserve antibiotic therapy, and, of course, we never routinely know if they express C5a peptidase.