Staphylococci Infections, Coagulase-Negative

Key Features

• An important cause of infections of intravascular and prosthetic devices and of wound infection after cardiothoracic surgery

• Less virulent than Staphylococcus aureus, and infections tend to be more indolent

• Normal flora of human skin

Clinical Findings

• Often associated with a foreign body or intravascular device

• Infection at the site of foreign body or device suggested by

  • Purulent or serosanguineous drainage

  • Erythema

  • Pain

  • Tenderness

• Evidence of prosthetic joint infection

  • Joint instability

  • Pain

• Evidence of prosthetic valve endocarditis

  • Fever

  • New murmur

  • Instability of the prosthesis

  • Signs of embolization

• Immunosuppression and recent antimicrobial therapy are risk factors for prosthetic valve endocarditis

Diagnosis

• Infection (vs isolation as a contaminant) is more likely if

  • Patient has a foreign body or an intravascular device in place

  • Same strain is consistently isolated from two or more blood cultures (particularly if samples were obtained at different times) and from the foreign body site

• Contamination: more likely when a single blood culture is positive or if > 1 strain is isolated from blood cultures

  • Antimicrobial susceptibility and speciation can help determine whether multiple strains have been isolated

  • More sophisticated typing methods (eg, pulse-field gel electrophoresis of restriction enzyme digested chromosomal DNA) may be required to identify distinct strains

Treatment

• Remove the foreign body or intravascular device when possible

  • Sometimes treatment with antibiotics is preferable

  • Surgical management may become necessary

• Vancomycin

  • Dosage: 1 g intravenously every 12 hours

  • Treatment of choice for patients with normal kidney function until susceptibility to penicillinase-resistant penicillins or other agents has been confirmed

• Duration of therapy is not established for infections caused by foreign devices, which may be eliminated by simply removing the device

• Treat bone or a prosthetic valve infection for 6 weeks

• Vancomycin plus rifampin, 300 mg twice daily orally, and gentamicin, 1 mg/kg intravenously every 8 hours, is recommended for prosthetic valve endocarditis caused by methicillin-resistant strains