| Organism | Lancefield group | Type of infection | Therapy |
|---|---|---|---|
| Streptococcus pyogenes | A | Pharyngitis and impetigo | Benzathine penicillin IM, 1.2 million U for adults; 600 000 U for children ≤27 kg Penicillin G or V, 400 000 U PO QID for 10 d for adults; 200 000 U QID for children ≤27 kg Erythromycin ethyl succinate, PO 40 mg/kg/d |
| Recurrent streptococcal pharyngitis, tonsillitis | Same as above or ampicillin + clavulanic acid, PO 20–40 mg/kg/d Oral cephalosporin Dicloxacillin, 500 mg PO QID for 10 d for adults Clindamycin, 10 mg/kg/d PO in 4 doses for 10 d | ||
| Cellulitis and erysipelas Necrotizing fasciitis, myositis, and streptococcal toxic shock syndrome | Nafcillin, 8–12 g/d IV for 7–10 d or penicillin or ceftriaxone in appropriate doses Clindamycin, 900 mg IV q8h and penicillin G, 4 million U IV q4h for adults. Duration until resolution of infection | ||
| Prophylaxis of rheumatic fever | Benzathine penicillin, 1.2 million U IM q28d Penicillin G, 200 000 U PO BID for children ≤27 kg Sulfadiazine, 1 g/d for patients >27 kg; 500 mg/d for patients ≤27 kg Erythromycin, 250 mg PO BID | ||
| Streptococcus agalactiae | B | Neonatal sepsis | Penicillin, IV 100 000–150 000 U/kg/d in 2–3 divided doses for infants ≤7 d of age |
| Postpartum sepsis Septic arthritis Soft-tissue infection Osteomyelitis Intrapartum prophylaxis | Penicillin, 200 000–250 000 U/kg/d IV in 4 divided doses for infants >7 d of age Ampicillin, 100 mg/kg/d IV in 2–3 divided doses for infants ≤7 d of age Ampicillin, 150–200 mg/kg/d IV in 4 divided doses for infants >7 d of age Ampicillin, 8–12 g IV in 4–6 divided doses or penicillin 12–24 million U/d for adults Penicillin or ampicillin as for neonatal sepsis or postpartum sepsis above Penicillin or ampicillin as for postpartum sepsis above 1. Aqueous penicillin G 5 million U IV loading dose followed by 2.5 million U q4h for 4 doses 2. Ampicillin 2 g IV loading dose followed by 1 g q4h for 4 doses | ||
| Streptococcus equi | C | Bacteremia Cellulitis | Penicillin as for streptococcal toxic shock syndrome above |
| Enterococcus faecalisa | D | Endocarditis Bacteremia Urinary tract infection Gastrointestinal abscess | Ampicillin + gentamicin |
| Streptococcus bovis | D | Bacteremia Abscesses | Penicillin as for Streptococcus equi above |
| Streptococcus canis | G | Bacteremia Cellulitis Pharyngitis | Penicillin as for Streptococcus equi above |
a Linezolid has activity against vancomycin-resistant enterococci (VRE). See Chapter 135, Enterococcus, for more details.
Prophylactic treatment for populations at risk (e.g., schools, military) is indicated during epidemics of streptococcal pharyngitis when rheumatic fever is prevalent. The incidence of rheumatic fever has declined in developed nations but flourishes in developing countries. Antistreptococcal prophylaxis should be continuous in individuals with a history of rheumatic fever. Benzathine penicillin given intramuscularly once each month has the greatest efficacy, although oral agents such as phenoxymethyl penicillin are also effective. In recent years, the US military has demonstrated that such prophylaxis, particularly benzathine penicillin, prevents epidemics of streptococcal infections among young soldiers living in crowded conditions. Routine follow-up culture to verify eradication is not recommended except in patients with a history of rheumatic fever. Following appropriate treatment for symptomatic pharyngitis, treatment is not needed for continued positive cultures unless symptoms recur.
Scarlet fever
Severe cases of scarlet fever were prevalent in the United States, western Europe, and Scandinavia during the nineteenth century, and mortality rates of 25% to 35% were not uncommon. In contrast, scarlet fever today is rare and, when it occurs, is very mild. The primary site of infection is usually the pharynx, although surgical site infections have also been described. Classically, a diffuse, erythematous rash with sandpaper consistency appears 2 days after the onset of pharyngitis. Circumoral pallor and “strawberry” tongue are common findings, and desquamation occurs approximately 6 to 10 days later. The cause of the rash is uncertain, although most agree that extracellular toxins, likely the pyrogenic exotoxins formerly called “scarlatina toxins,” are responsible. Treatment of the underlying infection with penicillin (see “Pharyngitis”) and general supportive measures are indicated. Specifically, severe hyperpyrexia (fevers to 107°F to 110°F [41.7°C to 43.3°C]) has been described, and antipyretics may be necessary to prevent febrile seizures, particularly in children.
Pyoderma (impetigo contagiosa)
Impetigo is a superficial vesiculopustular skin infection. Although S. aureus is the most common organism isolated in modern times, group A streptococcus is likely the most significant pathogen. Impetigo is most common in patients with poor hygiene or malnutrition. Colonization of the unbroken skin occurs first; then minor abrasions, insect bites, and so on initiate intradermal inoculation. Single or multiple thick, crusted, golden-yellow lesions develop within 10 to 14 days. Penicillin orally or parenterally, or bacitracin or mupirocin topically, is effective treatment and will reduce transmission of streptococci to susceptible individuals. None of these treatments, including penicillin, prevent poststreptococcal glomerulonephritis. Although S. aureus may cause impetigo, it has never been implicated as a cause of glomerulonephritis.
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