infectious diseases
Streptococcal Infections
Treatment of Streptococcal Infections
Usually penicillin (See also the Infectious Diseases Society of America’s2012 Practice Guidelines for the Diagnosis and Management of Group A Streptococcal Pharyngitisand the American Heart Association's2020 Contemporary Diagnosis and Management of Rheumatic Heart Diseasestatement.) Ordinarily, pharyngeal GABHS infections, including scarlet fever, are self-limited. Antibiotics shorten the course in young children, especially those with scarlet fever, but have only modest effect on symptoms in adolescents and adults. However, antibiotics help prevent local suppurative complications (eg, peritonsillar abscess), otitis media, and rheumatic fever. Penicillinis the drug of choice for pharyngeal GABHS infections. No isolate of GABHS has shown penicillin resistance clinically. However, some streptococcal strains appear to have in vitro tolerance to penicillin (ie, significantly decreased bactericidal effect of penicillin); the clinical significance of such strains is unclear. A single injection of benzathinepenicillin G600,000 units IM for small children (<27 kg) or 1.2 million units IM for children weighing ≥ 27 kg, adolescents, and adults usually suffices. Oral medications may be used if the patient can be trusted to maintain the regimen for the required 10 days. Choices include Penicillin V500 mg (250 mg for children < 27 kg) orally every 12 hours Amoxicillin50 mg/kg (maximum 1 g) once a day for 10 days (which is an effective substitute forpenicillin V) Oral narrow-spectrum cephalosporins (eg,cephalexin,cefadroxil) are also effective and can be used unless patients have an anaphylactic reaction to penicillin.Azithromycincan be used for a 5-day course of therapy, although macrolides are inactive againstFusobacterium necrophorum, a common cause of pharyngitis in adolescents and adults. Delaying treatment 1 to 2 days until laboratory confirmation increases neither the duration of disease nor the incidence of complications. When penicillin and a beta-lactam are contraindicated,choices include Clindamycin600 mg (7 mg/kg for children) orally every 8 hours for 10 days Clarithromycin250 mg (7.5 mg/kg for children) orally every 12 hours for 10 days Azithromycin500 mg (15 mg/kg for children) orally once a day for 5 days Cephalexin500 mg (20 mg/kg for children; maximum dose is 500 mg/dose) orally every 12 hours for 10 days Cefadroxil1000 mg (30 mg/kg for children; maximum dose is 1000 mg/dose) orally once a day or 500 mg (15 mg/kg for children; maximum dose is 500 mg/dose) every 12 hours for 10 days Because resistance of GABHS to macrolides has been detected, some authorities recommend in vitro confirmation of susceptibility if a macrolide is to be used and there is macrolide resistance in the community.Clindamycin7 mg/kg orally every 8 hours is preferred in children who have relapses of chronic tonsillitis, possibly because of the following: Clindamycinhas good activity against penicillinase-producing staphylococci or anaerobes coinfecting the tonsillar crypts and inactivatingpenicillin G. It appears to halt exotoxin production more rapidly than other medications. Amoxicillin/clavulanate is also effective. Trimethoprim/sulfamethoxazole (TMP/SMX), some of the fluoroquinolones, and tetracyclines are unreliable for treating GABHS infection. Sore throat, headache, and fever can be treated with analgesics or antipyretics.Aspirinshould be avoided in children. Bed rest and isolation are unnecessary. Close contacts who are symptomatic or have a history of poststreptococcal complications should be examined for streptococci. Cellulitisis often treated without doing a culture because isolating organisms can be difficult. Thus, regimens effective against both streptococci and staphylococci are used; for example, one of the following may be used: Dicloxacillinorcephalexinif methicillin-resistantStaphylococcus aureus(MRSA) is not likely if MRSA is suspected (see Treatment ) Necrotizing fasciitisshould be treated in an intensive care unit. Extensive (sometimes repeated) surgical debridement is required. A recommended initial antibiotic regimen is a broad-spectrum beta-lactam (eg,piperacillin/tazobactam) or a carbapenem (eg,meropenem, imipenem) (until etiology is confirmed by culture) plusclindamycin.Vancomycinshould be added if infection with MRSA is suspected. Although streptococci remain susceptible to beta-lactam antibiotics, animal studies show that penicillin is not always effective against a large bacterial inoculum because the streptococci are not rapidly growing and may lack penicillin-binding proteins, which are the target of penicillin activity. For treatinggroups B, C, and G infections,antibiotics of choice are Penicillin Ampicillin Vancomycin Cephalosporins or macrolides are usually effective, but susceptibility tests must guide therapy, especially in very ill, immunocompromised, or debilitated people and in people with foreign bodies at the infection site. Surgical wound drainage and debridement as adjuncts to antimicrobial therapy may be lifesaving. S. gallolyticus(formerlyS. bovis) is relatively susceptible to antibiotics. Althoughvancomycin-resistantS. gallolyticusisolates have been reported, the organism remains susceptible to penicillin and aminoglycosides. Mostviridans streptococciare susceptible topenicillin Gand other beta-lactams. Resistance is growing, and therapy for such strains should be dictated by results of in vitro susceptibility tests. 