June 22, 1984

Apparent Failure in Endocarditis Prophylaxis

Author Affiliations

Evanston Hospital Evanston, III

JAMA. 1984;251(24):3222. doi:10.1001/jama.1984.03340480015009

To the Editor.—  The article by Durack et al reports 52 cases of apparent endocarditis prophylaxis failure. Two of their conclusions we found particularly interesting. First, endocarditis prevention failures are not rare. Second, failure of attempted endocarditis prophylaxis may occur even when the organism is sensitive in vitro to the antibiotic used. In 63% of their reported cases for which antimicrobial susceptibility data were available, the infecting organism was susceptible to the antibiotic used for prophylaxis. While most patients received prophylaxis regimens now regarded as inadequate, five patients infected with viridans streptococci received a recommended American Heart Association antibiotic regimen as prophylaxis. Four of those strains were susceptible to the antibiotic given. In one strain, the sensitivity pattern was unknown. It is not clear, however, by which method susceptibility was determined. This becomes very important when considering the concept of tolerance.Tolerant organisms are those that are inhibited at standard