Do you use combination antibiotic therapy for treatment of bacterial endocarditis due to gram-negative bacilli?
The approach towards different might differ depending on whether the culprit organism belongs to the HACEK group or the nonHACEK group. The mortality rates per literature were approximately 2% for HACEK and 20-30% for the nonHACEK group.
Combination therapy is usually not recommended for HACEK endocarditis due to the risk of harm. Currently, the treatment of choice for HACEK-IE is either third-generation cephalosporins or fluoroquinolones.
NonHACEK endocarditis, which is usually healthcare-associated or IVD-use-related, guidelines do recommend combination therapy (penicillins, cephalosporins, or carbapenems and either an aminoglycoside or fluoroquinolone) often combined with early surgery. Antimicrobial recommendations are based on low-quality evidence and expert opinion. The absence of benefit of combination therapy was supported in the recent case series published by Shaw et al., 2023 and Lorenz, Ashley et al., 2021. Monotherapy seems appropriate till data from high-quality evidence becomes available. When an indication existed, a lack of surgical intervention was associated with worse outcomes in Shaw et al., 2023. Therefore, combination therapy might be appropriate for select patients. I resorted to combination therapy in my personal experience managing PWID with nonHACEK endocarditis, where surgery was deferred for other reasons (primarily recidivism), and I noticed mixed results.
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