Group G Streptococci: To Treat or Not to Treat?

December 31, 2006

Our laboratory has begun reporting group G β-hemolytic streptococci in addition to group A on throat cultures.

Our laboratory has begun reporting group G β-hemolytic streptococci in addition to group A on throat cultures. In this setting, are group G streptococci considered pathogens that warrant treatment or normal flora? -- John Mosby, MD
    Charleston, SC

The answer to your question is "both." Group G streptococci are considered part of the normal flora of the pharynx, skin, GI tract, and female genital tract. Group G streptococci can cause pharyngitis, and several well-characterized outbreaks that stemmed from food contamination have been reported.1 However, I am unaware of any documentation of acute rheumatic fever or glomerulonephritis secondary to group A streptococcal pharyngitis. Therefore, antimicrobial treatment is not indicated for uncomplicated cases of "sore throat" in which this microorganism is isolated.1-4 However, there is mounting evidence that group G streptococci sometimes cause serious and even life-threatening infections in other settings. The most frequently encountered are probably soft tissue infections, such as cellulitis, in elderly men; these infections often lead to bacteremia.5 Group G streptococcal soft tissue infections resemble those caused by group A streptococci and include necrotizing fasciitis ("flesh-eating bacteria syndrome"). Other syndromes that have been associated with group G streptococci are endocarditis, puerperal sepsis, neonatal sepsis, pleuropulmonary infections, bone and joint infections, and endophthalmitis.1,6 Humar and colleagues7 demonstrated that group G streptococci sometimes produce an exotoxin similar to that produced by group A streptococci. When treating an infection caused by group G streptococci, be aware that resistance to various antibiotics--including macrolides--can be a problem. The drugs most effective against group G streptococci are penicillin, ampicillin, and cefotaxime (or ceftriaxone). Clindamycin and erythromycin have relatively poor bactericidal activity against this pathogen. Endocarditis caused by group G streptococci is usually treated with an aminoglycoside (such as gentamicin) plus either a β-lactam antibiotic (such as penicillin or ceftriaxone) or, in patients who are allergic to penicillin, vancomycin. However, in most infections encountered in ambulatory care practice, it is not necessary to add an aminoglycoside. -- Charles S. Bryan, MD
    Professor of Medicine
    University of South Carolina School of Medicine


REFERENCES: 1. Stryker WS, Fraser DW, Facklam RR. Foodborne outbreak of group G streptococcal pharyngitis. Am J Epidemiol. 1982;116:533-540.
2. Vartian C, Lerner PI, Shlaes DM, Gopalakrishna KV. Infections due to Lancefield streptococci. Medicine (Baltimore). 1985;64:75-88.
3. Hill HR, Caldwell GG, Wilson E, et al. Epidemic of pharyngitis due to streptococci of Lancefield group G. Lancet. 1969;2:371-374.
4. McCue JD. Group G streptococcal pharyngitis. Analysis of an outbreak at a college. JAMA. 1982;248: 1333-1336.
5. Sylvetsky N, Raveh D, Schlesinger Y, et al. Bacteremia due to beta-hemolytic Streptococcus group G: increasing incidence and clinical characteristics of patients. Am J Med. 2002;112:622-626.
6. Ritterband DC, Shah MK, Buxton DJ, et al. A devastating ocular pathogen: beta-streptococcus Group G. Cornea. 2000;19:297-300.
7. Humar D, Datta V, Bast DJ, et al. Streptolysin S and necrotising infections produced by group G streptococcus. Lancet. 2002;359:124-129.