is an uncommon cause of infective endocarditis (IE) and, despite the fact that synergy between beta‐lactam antibiotics and aminoglycosides has not been demonstrated for lactococci, combination therapy is often used.

Case presentation:

We report a case of suspected IE in an 82‐year‐old man, which was successfully treated with a combination of ampicillin and gentamicin. Despite careful dosing and monitoring of gentamicin levels, the patient developed a transient decrease in renal function and permanent bilateral vestibular deficiency. The combination of gentamicin and ampicillin did not demonstrate synergistic killing effects against the isolate from this patient. However, synergy was noted against two of the four isolates tested. Unfortunately, an Etest‐based method, which would be easy to use in a routine laboratory, was unable to predict synergy in the time‐kill methods.


The use of combination therapy in IE is based solely on synergy between beta‐lactams and aminoglycosides. Here we demonstrate that a combination of ampicillin and gentamicin induces synergistic killing only of some isolates. Since synergy does not seem to be omnipresent, the risks for aminoglycoside toxicity must be carefully weighed against the potential theoretical benefit of combination therapy in IE.

  • This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/).

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