Prosthetic valve endocarditis caused by Staphylococcus capitis: report of 4 cases

Staphylococcus capitis (S. capitis) is considered to be a rare causative organism of prosthetic valve endocarditis (PVE) since only 4 cases of PVE caused by S. capitis have been reported to date [1-3]. This bacterium is a subtype of coagulase-negative staphylococci (CoNS) and thus produces biofilm, which confers tolerance to disinfectants during surgery. Unlike most CoNS, however, the adhesion ability of S. capitis to foreign body surfaces is low [4,5]. Nonetheless, we report here 4 cases of PVE caused by S. capitis that were encountered at our hospital over the past 2 years.A 79-year-old woman underwent aortic valve replacement with a Carpentier-Edwards Magna bioprosthetic valve (Edwards Lifesciences, Irvine, CA) for aortic stenosis. She presented with a fever of over 38°C 24 days after the procedure (Table 1). The first blood culture showed no evidence of bacterial growth, but S. capitis was detected in the second examination. Intravenous administration of gentamicin (GM) was started, which was later changed to abekamicin due to its susceptibility (Table 2). Transesophageal echocardiography (TEE) revealed an annular abscess in the aorto-mitral continuity and mild perivalvular regurgitation. We performed emergency surgery 5 days after the diagnosis of PVE was made. The aortic bioprosthesis was fully covered with a yellowish-white film, and vegetation was seen on the right coronary cusp. Valve dehiscence had occurred around the commissure between the left and non-coronary cusps (Figure 1). The prosthetic valve was removed and the aortic annulus debrided. The intimal defect around the commissure was repaired after debridement with an autologous pericardial patch (Figure 2). A Medtronic Mosaic porcine valve (21 mm) (Medtronic, Minneapolis, MN) was implanted in a supra-annular fashion with horizontal mattress sutures from the left ventricle to the ascending aorta, except for 5 sutures that were passed through the aortic wall and pericardial patch at the intimal defect.