Do you add gentamicin when treating prosthetic valve endocarditis secondary to viridans group Streptococcus with a penicillin-intermediate isolate (MIC >0.125 - <0.5)?
Do you add gentamicin when treating prosthetic valve endocarditis secondary to viridans group Streptococcus with a penicillin-intermediate isolate (MIC >0.125 - <0.5)?
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No, we do not treat patients with such infections with a combination of penicillin and gentamicin.
For these infections, we treat with ceftriaxone alone. Monotherapy with ceftriaxone is a more reasonable option than a combination of penicillin and gentamicin because we have every reason to consider it to be as effective, is more convenient to administer, has less potential for toxicity, and is far less expensive (in the USA).
It will bear emphasizing, that for prosthetic valve endocarditis, the first consideration is an evaluation of whether patients require surgery. This is a more important decision than the choice of antibiotic, and should be done by individuals who have the experience to make a reasoned judgment on the matter. By the time prosthetic valve endocarditis is diagnosed, a substantial proportion of patients have already reached a stage where the infection cannot be cured without surgery.
Thanks for the helpful answer by Dr. @Dr. First Last. I also abandoned gentamicin a few years ago. Too toxic, especially for a contemplated duration of 6 weeks, in my very elderly population, most of whom have diabetes and vascular disease.
I think there is very good data even since the 1980s that in STAPH endocarditis, gentamicin was beneficial to clear blood cultures more quickly, but at a cost of increased renal toxicity, and no benefit on mortality nor morbidity. I'm willing to believe that the situation with streptococci is much the same. A laboratory benefit, but not a meaningful clinical benefit.
Usually use a double B-lactam (e.g., ceftriaxone, amoxicillin). The majority of PVEs (Strep and others) are in more elderly patients who are especially prone to renal or vestibular toxicity from prolonged courses of aminoglycosides. Genta (or tobra) is reserved for those rare, desperate cases with evidence of active, ongoing infection despite prior Rx.