Approach to managing streptococcal endocarditis

Baddour, 2015Habib, 2015

Streptococci are the second most common cause of infective endocarditis. Endocarditis caused by viridans streptococci and Streptococcus bovis group (now classified as Streptococcus gallolyticus or Streptococcus infantarius) is usually susceptible to penicillin. However, up to 20% of viridans streptococci may have dose-dependent susceptibility (ie susceptible dose dependent [SDD] or susceptible increased exposure [I or SIE]) or resistance to penicillin. Therefore, the minimum inhibitory concentration (MIC) for penicillin must be obtained to guide therapy.

Patients with endocarditis secondary to S. bovis group should be investigated for a concurrent bowel neoplasmOlmos, 2016.

Endocarditis caused by other non-viridans streptococci is rare – seek expert advice.

Management of infective endocarditis should involve a multidisciplinary team-based approach; see Approach to managing infective endocarditis.

Treatment of streptococcal endocarditis may require weeks of gentamicin therapy. Monitor the gentamicin plasma concentration and regularly assess for nephrotoxicity as well as vestibular and auditory toxicity – see Gentamicin in the management of infective endocarditis. Although multiple-daily dosing of gentamicin is recommended for the treatment of streptococcal endocarditis, once-daily dosing (3 mg/kg) may be appropriate for patients receiving ambulatory antimicrobial therapy – seek expert advice.

For principles of antimicrobial therapy for infective endocarditis (including duration of therapy following valve surgery and considerations for ambulatory antimicrobial therapy), see Principles of antimicrobial therapy for infective endocarditis.

Treatment recommendations are included below for endocarditis caused by viridans streptococci and S. bovis group with:

• penicillin MIC 0.125 mg/L or lower
• penicillin MIC greater than 0.125 mg/L and less than or equal to 0.5 mg/L
• penicillin MIC greater than 0.5 mg/L and less than or equal to 2 mg/L
• resistance to penicillin (MIC greater than 2 mg/L).