Comment on: The role of aminoglycosides in combination with a -lactam for the treatment of bacterial endocarditis: a meta-analysis of comparative trials

Abstract

Sir, Falagas and colleagues performed a meta-analysis of comparative trials to determine the role, if any, of aminoglycosides in combination with a b-lactam antibiotic for the treatment of infective endocarditis caused by Gram-positive cocci. 1 They are to be congratulated on their thorough analysis and their many fine contributions to the literature. One point in the Discussion section of the article 1 deserves further clarification. The authors state that ‘the addition of gentamicin to penicillin G or ceftriaxone is highly recommended by the AHA for the first 2 weeks of treatment’ in the latest published statement 2 and that findings from their meta-analysis did not support this position. As outlined in their review, only one trial 3 that pertained to streptococci was included in the analysis and that investigation examined monotherapy versus dual therapy for native valve endocarditis caused by either viridans group streptococci or Streptococcus bovis. It is noteworthy that only patients who had streptococcal isolates that were susceptible to penicillin, ceftriaxone and gentamicin were included in the study; ‘resistance’ to penicillin of the initial blood culture isolate was an exclusion criterion. The authors did not, however, provide the specific in vitro susceptibility data (MIC) for the isolates. Due to the success of b-lactam monotherapy in this trial 3 and other investigations, both the current 2 and previous 4 versions of the AHA ‘treatment guidelines’ listed only b-lactam monotherapy as a 4 week treatment option for native valve endocarditis caused by penicillin-susceptible (MIC £ 0.12 mg/L) viridans group streptococci and S. bovis. The current guidelines do recommend that the first 2 weeks of treatment of native valve endocarditis caused by streptococci that have higher (>0.12 to £0.5 mg/L) MICs of penicillin receive combination therapy with gentamicin.