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ENDOCARDITIS CAUSED BY STAPHYLOCOCCUS LUGDUNENSIS

2002; Lippincott Williams & Wilkins; Volume: 21; Issue: 3 Linguagem: Inglês

10.1097/00006454-200203000-00025

1532-0987

Rebecca Jones, Mary Anne Jackson, Catherine Ong, Gary K. Lofland,

Streptococcal Infections and Treatments

We describe a case of native valve endocarditis caused by Staphylococcus lugdunensis, a perineal skin commensal, and review 28 other cases from the medical literature. Correctly identifying this coagulase-negative organism is critical because endocarditis is usually associated with left sided valvular disruption and life-threatening embolic complications, reminiscent of disease caused by Staphylococcus aureus. Urgent surgical intervention is necessary in most cases. Coagulase-negative staphylococci have generally been considered nonpathogenic commensals, although clinical disease is well-reported among immunocompromised hosts and in the presence of indwelling foreign bodies. 1Staphylococcus lugdunensis, first described by Freney et al. 2 in 1988, is a coagulase-negative staphylococcus, which can be differentiated from other coagulase-negative species by its ability to produce ornithine decarboxylase and pyrrolidonyl arylamidase. It is characterized by its propensity to cause fulminant clinical disease among otherwise healthy hosts including endocarditis, septicemia, brain abscess, peritonitis, soft tissue infection and vascular graft infection. 3 To date 30 cases of endocarditis caused by S. lugdunensis have been reported. We present a case of endocarditis in a 16-year-old boy, the youngest patient reported yet. Our review highlights the destructive nature of this pathogen, its predilection for native valves and the need for aggressive surgical intervention. Case report. A 16-year-old boy with a previous history of congenital aortic stenosis presented to Children's Mercy Hospital, Kansas City, with a 10-day history of fever to 40°C and malaise. He had undergone balloon angioplasty 4 years previously and subsequently was noted to have mild aortic insufficiency. His father reported that the patient had recently worked part-time as a groundskeeper for an apartment complex, during which time he had incurred a number of small scratches over his lower extremities that he attributed to cuts from using a hand-held weed eater. At the time of admission the patient was febrile and had a harsh grade 3/6 holosystolic murmur at the apex. Multiple small superficial scratches were noted over the patient's lower extremities. There were no peripheral stigmata suggestive of endocarditis. The white blood cell count was 6800 with a hemoglobin of 12.7 g/dl and a platelet count of 171 000/mm 3. The erythrocyte sedimentation rate was 42 mm/h. Chest radiograph showed moderate cardiomegaly. Three blood cultures from the referring hospital as well as three blood cultures obtained at our institution yielded coagulase-negative Staphylococcus subsequently identified as S. lugdunensis. The organism was susceptible to penicillin, oxacillin, cefazolin, erythromycin, rifampin and gentamicin, with MICs of ≤.03, ≤0.5, ≤2, ≤.25, ≤1 and ≤1, respectively. Transthoracic echocardiography demonstrated a thickened aortic valve with mild stenosis and moderate aortic insufficiency and a possible ventricular-septal defect. In light of the positive blood cultures, a transesophageal echocardiogram was performed. Vegetations were seen in the right atrium, on the left ventricular septum and on the mitral valve. An abnormal aortic valve with a large vegetation near the right coronary cusp was noted, and a left ventricular-to-right atrial communication extended between the vegetations in those cavities. Oxacillin and gentamicin were initiated intravenously in a dose of 2 g every 6 h with gentamicin given in a dose of 80 mg every 8 h. Blood culture was sterile on Day 4 at which time peak bactericidal activity was documented at 1/64 and trough bactericidal activity at 1/16. The patient remained febrile for 9 days, and vomiting requiring intravenous fluids and parenteral nutrition complicated his course. A computed tomography scan of the head was normal as was magnetic resonance imaging of the brain. Ophthalmologic examination was also negative. On Day 28 of therapy surgical repair was performed. Intraoperatively there was an extremely dysplastic aortic valve, disruption of the aortic annulus with a sinus of Valsalva aneurysm, perforation of the anterior mitral valve leaflet and a ventricular-septal defect with left ventricular-to-right atrial flow. The septal tricuspid valve leaflet also had a perforation. Surgery consisted of debridement and repair of the mitral and tricuspid valve leaflets, closure of the ventricular-septal defect and reconstruction of the aortic outflow tract by a modified Ross procedure. Cultures of the vegetations were negative, but pathology of aortic and mitral valves revealed acute necrotizing endocarditis, and a few isolated Gram-positive cocci were seen on a stained smear. The patient completed 8 weeks of antimicrobial therapy, and at follow-up 3 years later he remains well. Discussion. Coagulase-negative staphylococci are recognized as the most commonly isolated pathogens in prosthetic valve endocarditis and are known to cause native valve endocarditis in those with indwelling intravascular catheters. 4 A subacute presentation is typical, Staphylococcus epidermidis is the most frequently reported coagulase-negative species and surgical removal of the infecting foreign body is often necessary for clinical success in diseased prosthetic valves. In patients with intravascular catheters and native valve involvement, congestive heart failure and embolic events are infrequent complications, surgical intervention is required in less than one-half of cases and lower case fatality rates have been reported. 5 In contrast an acute presentation and aggressive course reminiscent of disease caused by Staphylococcus aureus is noted in cases of endocarditis caused by S. lugdunensis. Thirty cases abstracted from the English literature illustrate the classic features of endocarditis caused by this unusual pathogen (Table 1). 6–19 The majority of patients described were older than 50 years, and the infection involved native aortic or mitral valves in 21 cases. The presence of an indwelling vascular graft or catheter was noted in 3 patients, and a pacemaker was present in 2 others who had native valve infection. Prosthetic valve infection, usually aortic or mitral, was reported in 7 patients.Table 1: Staphylococcus lugdunensis endocarditis cases as reported in the literature, 1988 to 2000Three patients younger than 35 years are reported, in addition to our case. A bicuspid aortic valve was present in 3 of 3 healthy individuals and 1 patient had an indwelling Hickman catheter. Lamas and Eykyen 21 deemed the bicuspid aortic valve a "silent danger" in a report that detailed clinical manifestations in 50 cases of bicuspid aortic valve endocarditis. Most patients were young men, and few were aware of their underlying heart disease at the time of presentation with endocarditis. Transthoracic echocardiography failed to demonstrate vegetations or the extent of valvular disease in two of two patients in whom detailed data were available. This is consistent with previous reports that note sensitivity for detection of endocarditis for transthoracic vs. transesophageal echocardiograms to be 50%vs. 90%, respectively. 20 As in cases of S. lugdunensis endocarditis reported in the older patient, clinical presentation in patients younger than 35 years was acute, and complications including valve perforation, congestive heart failure and embolic phenomena were common. Surgical intervention was documented in three of four. Case fatality rates in both age groups are >50% for those reported in the literature. Coagulase-negative staphylococci are generally regarded as contaminants in healthy individuals, and speciation is not performed. Failure to identify S. lugdunensis in blood culture in a febrile patient without known cardiac disease would likely be associated with a significant delay in treatment with a concomitant increase in morbidity and mortality. Standard laboratory methodology should allow for isolates of coagulase-negative staphylococci to be correctly identified as lugdunensis species, and speciation should be mandatory for cases where there are multiple positive isolates. The portal of entry for S. lugdunensis in our case was presumably the skin and related to minor injuries scattered over the lower extremities caused by a hand-held gardening tool. Similarly in more than one-half of the cases reported, the skin appeared to be the portal of entry and related to cutaneous injuries or indwelling foreign bodies. Although most coagulase-negative staphylococci are skin commensals, the perineal skin has been associated with a particularly high colonization rate for S. lugdunensis. 13 Four patients recently described with S. lugdunensis endocarditis after vasectomy lend support to the concept that perineal associated skin breaks are an important portal of entry for S. lugdunensis. Susceptibility data in most cases of S. lugdunensis endocarditis demonstrate low MICs for oxacillin, cephalosporins and rifampin in contrast to most other coagulase-negative staphylococcal species. 22 Therapy should be guided by susceptibility data, and in most instances a beta-lactam plus rifampin or gentamicin is adequate therapy. However, because of the destructive nature of this pathogen, surgical intervention is almost always necessary, even if the patient demonstrates a good clinical response, has negative blood cultures and demonstrates good serum bactericidal activity. In conclusion clinicians must be aware of the potential for this coagulase-negative staphylococcus to cause fulminant endocarditis associated with a high case fatality rate. S. lugdunensis must be appropriately identified in blood culture isolates, and when identified in the febrile patient the possibility of endocarditis should be considered. Left sided disease is typical, and transesophageal echocardiography should be utilized to demonstrate accurately the extent of disease. The propensity for these organisms to cause valvular disruption and life-threatening embolic complications should be recognized. Surgical intervention is necessary in almost all cases, and valve replacement may be required on an urgent basis.