Native valve endocarditis due to coagulase-negative staphylococci. Clinical and microbiologic features

Twenty-one patients with native valve endocarditis caused by coagulase-negative staphylococci were studied; 14 had pre-existing valvular or congenital heart disease. Although commonly subacute in presentation, complications of endocarditis were frequent: arterial emboli in five patients, new electrocardiographic conduction system abnormalities in nine, congestive heart failure in eight, annular or myocardial abscesses in five, and disruption of valve leaflets in three. Cures were achieved in 10 of 12 patients treated medically and seven of nine treated surgically. In microbiologic studies of 16 coagulase-negative staphylococci from patients with endocarditis, only eight were identified as Staphylococcus epidermidis. All isolates were susceptible to vancomycin. Antibiotic resistance (methicillin, four isolates; gentamicin, two isolates; rifampin, one isolate) was usually associated with nosocomial acquisition of endocarditis. Rather than representing contamination, coagulase-negative staphylococci in blood cultures may indicate life-threatening endocarditis. However, with careful attention to the selection of antibiotics for therapy and to the occurrence of heart failure due to intracardiac complications, treatment of this form of endocarditis is frequently successful. Organisms must always be tested for cryptic resistance to beta-lactam antibiotics. Valve replacement may be required frequently.