Clinical and microbiologic aspects of serious infections caused by Staphylococcus epidermidis

10 patients with serious infections caused by Staphylococcus epidermidis (8 cases of endocarditis in non-prosthetic valves, 1 was complicated by osteomyelitis, 1 case of osteomyelitis, and 1 case of septicemia) are described. Clinical and microbiologic features were evaluated including antibiotic sensitivity and synergy studies, phage typing and biotyping. Endocarditis tended to affect the elderly population and the clinical manifestations were quite similar to those caused by Streptococcus viridans. Both patients with osteomyelitis had involvement of the cervical spine with excellent response to antibiotic therapy. The only patient with septicemia acquired via hyperalimentation had delayed clearance of the bacteremia but ultimately responded to intravenous antibiotics. Rifampicin was the most effective of all antibiotics tested. All isolates were sensitive to penicillinase-resistant penicillins and cephalosporins and over half were sensitive to penicillin. Full synergistic activity was demonstrated with cephalothin and nafcillin in combination with rifampicin, and rifampicin-vancomycin was partially synergistic against the majority of the strains. Five of 8 available isolates were non-phage typeable and no definite pattern was established for various types of infections. Four of the 8 isolates were classified as biotype SIIa, 2 biotype SIIc and 2 biotype SVh.