Comment on: Bactericidal activity of antibiotic combinations against clinical isolates of Enterococcus gallinarum and Enterococcus casseliflavus

We read with interest the report by Landman and coworkers that a combination of ampicillin and ceftriaxone was not synergistic against Enterococcus gallinarum and Enterococcus casseliflavus in vitro.1 We believe that this report is important because there is a risk that ampicillin and ceftriaxone or cefotaxime, which have synergistic effects against Enterococcus faecalis2and are used to treat infective endocarditis caused by this pathogen,3 may be used to treat infections caused by other enterococci. Non-faecalis, non-faecium enterococci are increasingly reported as human pathogens4 and there is no indication that ampicillin plus ceftriaxone is synergistic against such enterococci. A 72-year-old woman who had both mitral and aortic biological valve prostheses, a pacemaker due to a third-degree atrioventricular block and chronic renal failure presented with recurrence of bacteraemia with E. gallinarum to our hospital. On the first occasion of bacteraemia, the woman was diagnosed with mitral valve infective endocarditis and was treated with ampicillin and ceftriaxone, based on a presumed synergy against the isolate, for 6 weeks. At relapse, 12 months later, she presented with long-standing symptoms of infection, and echocardiography revealed a large mitral vegetation leading to partial obstruction. Surgery was indicated but was deemed to be impossible due to pronounced frailty of the patient. She was treated with a combination of ampicillin and gentamicin for 6 weeks and she was discharged with oral suppressive therapy with amoxicillin 1 g daily. The patient sadly passed away after only 1 week in her home. We investigated whether the ampicillin and ceftriaxone combination, given to the patient during the first hospitalization, was synergistic against the E. gallinarum isolate. We also investigated this for other isolates of uncommon enterococci using a methodology different to that employed by Landman and coworkers.1