Group A β-hemolytic streptococci (Streptococcus pyogenes) cause a variety of acute suppurative infections via droplet transmission. Suppurative streptococcal infections in humans include pharyngitis, impetigo, pneumonia, erysipelas, wound and burn infections, puerperal infections, and scarlet fever. Rapid identification with antigen detection tests allows prompt treatment of patients with pharyngitis due to this strain of Streptococcus and can reduce the risk of spread of infection.
Streptococcus pyogenes remains highly susceptible to penicillin G; however, in the presence of allergy, erythromycin or (if no cross-allergy exists) a cephalosporin is substituted. Macrolide-resistant and clindamycin-resistant strains of group A β-hemolytic streptococci have been reported.
Streptococcus pneumoniae are lancet-shaped diplococci that cause α-hemolysis on blood agar. Although 10%–30% of the general population carry 1 or more serologic types of pneumococci in the throat, the incidence of and mortality from pneumococcal pneumonia increase sharply after 50 years of age, with a fatality rate approaching 25%.
Besides pneumonia, conditions caused by S pneumoniae include sinusitis, meningitis, otitis media, and peritonitis. Pneumococci are usually highly susceptible to penicillin, other β-lactams, erythromycin, or the newer fluoroquinolones. Routine susceptibility testing should be performed on patients with meningitis, bacteremia, or other life-threatening infections. Penicillin-resistant strains of S pneumoniae have been reported with increasing frequency. Treatment of highly resistant strains may require vancomycin or meropenem. Prophylaxis is available through use of the 23-valent pneumococcal conjugate vaccine for adults and the 13-valent vaccine for children (see Chapter 12 in this volume).
Between 10% and 35% of cases of community-acquired infectious endocarditis are caused by α-hemolytic streptococci, while S aureus accounts for 30%–50% of cases. S aureus also accounts for 60%–80% of cases of nosocomial endocarditis, with the majority due to MRSA. Prophylaxis for infectious endocarditis is usually not considered necessary for routine ocular surgery but can be considered for surgery involving the nasolacrimal drainage system, the sinuses, or for surgical repair of orbital trauma, if the patient has a high risk of adverse outcome from endocarditis (Table 14-1). These include patients with prosthetic cardiac valves or prosthetic material used to repair cardiac valves, previous endocarditis, certain types of congenital heart disease, and cardiac transplantation with valve regurgitation.
Grabenstein JD, Musey LK. Differences in serious clinical outcomes of infection caused by specific pneumococcal serotypes among adults. Vaccine. 2014;32(21):2399–2405.
Table 14-1 SBE Prophylaxis Regimens for Dental and Incisional Nasolacrimal Procedures
Habib G, Lancellotti P, Antunes MJ, et al; ESC Scientific Document Group. 2015 ESC Guidelines for the management of infective endocarditis: the Task Force for the Management of Infective Endocarditis of the European Society of Cardiology. Eur Heart J. 2015;36(44):3075–3128.
Nishimura RA, Otto CM, Bonow RW, et al. 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. J Am Coll Cardiol. 2017;70(2):252–289.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.