Diagnosis and management of staphylococcal infections of vascular grafts and stents

Staphylococcus aureus and coagulase-negative staphylococci are the commonest bacterial causes of both vascular graft and stent infections. Infection may occur either from direct implantation or haematogenous spread, and occurs in less than 1% of aortic grafts, 2% to 5% of inguinal grafts, and rarely in stents. Death or amputation is common following these infections despite aggressive treatment. Infection with S. aureus is usually more acute than with coagulase-negative staphylococci but both cause systemic symptoms. Inguinal infections usually cause localized swelling often with a sinus tract, bleeding or distal embolism. Aortic infections commonly present with abdominal discomfort retroperitoneal infection or a mass from a false aneurysm. Stent infections usually cause pain, swelling, erythema and circulation disturbances of the ipsilateral limb. The most useful investigations are blood cultures and computerized tomography or magnetic resonance imaging. These imaging techniques have a high sensitivity and specificity in advanced graft infections but these are considerably lower in low-grade infections. Persistence of perigraft fluid beyond 3 months after surgery is suspicious of infection. Aggressive antimicrobial therapy is an important part of management but surgery is usually required to cure both graft and stent infections. Where the organisms are susceptible, high-dose beta-lactam therapy (e.g. flucloxacillin, dicloxacillin or a first-generation cephalosporin) plus low-dose gentamicin are recommended initially. Some authorities add rifampicin after 3 - 5 days treatment, but this is controversial. Antimicrobial therapy can be stopped 4 - 6 weeks after surgery if arterial stump cultures are negative but should be continued long-term, and perhaps indefinitely, if they are positive.