A case of suspected infective endocarditis with Lactococcus garvieae: lack of in vitro synergy between ampicillin and gentamicin

Abstract

Introduction: Lactococcus garvieae 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 L. garvieae 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 in vitro against the L. garvieae isolate from this patient. However, synergy was noted against two of the four L. garvieae 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. Conclusions: The use of combination therapy in IE is based solely on in vitro synergy between beta‐lactams and aminoglycosides. Here we demonstrate that a combination of ampicillin and gentamicin induces synergistic killing only of some L. garvieae 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 L. garvieae IE.

Infective endocarditis due to Streptococcus dysgalactiae: clinical presentation and microbiological features

“…Synergy was defined as ΣFIC ≤ 0.5. In order to test bactericidal synergy, the time-kill technique was applied as described by Weinstein [26] with certain modifications [27]. Synergy was defined if a > 2 log 10 cfu/ml difference between the drugs in combination, as compared to the most effective active single antibiotic alone, at one given time point (6 or 24 h).…”

Native valve endocarditis caused byLactococcus garvieae: an emerging human pathogen

“…Although lack of synergism with aminoglycosides have been reported in some isolates of L. garvieae ,10 the relatively high penicillin MIC of this isolate compared with other streptococci prompted the decision to use combination treatment in this patient.…”

Familial Adenomatous Polyposis Manifesting asLactococcusEndocarditis: A Case Report and Review of the Association ofLactococcuswith Underlying Gastrointestinal Disease

“…While he did not have direct or echocardiographic evidence of intracardiac infection at the time of diagnosis, the patient's clinical presentation was consistent with prosthetic valve IE, and it was recommended that he receive a six-week course of antibiotic therapy with ceftriaxone and gentamicin based on the minimal inhibitory concentration (MIC) noted on Etest. This regimen was derived from traditional recommendations for the treatment of prosthetic valve IE caused by intermediate resistance viridans group streptococci or Streptococcus bovis [12], although the synergistic effect of gentamycin has been proven to be limited in the treatment of L. garvieae [13]. The patient was only able to complete two of the six weeks of gentamicin therapy due to the development of acute kidney injury.…”

“…In particular, L. garvieae has been more broadly associated with fish and dairy consumption, with transmission also reported via contaminated water; conversely, L. lactis is associated primarily with dairy products [8, 9]. Importantly, in many of the reported cases, these patients had underlying gastrointestinal (GI) disease, suggesting a portal of entry [1, 5, 7, 10–13]. While not normally part of the GI microbiome, Lactococcus has been isolated from the intestines of humans [1, 10].…”