What is the most common cause of prosthetic graft infection: Gram-positive (G+) cocci, Gram-positive (G+) bacilli, Gram-negative (G-) cocci, or Gram-negative (G-) bacilli?

From the Guidelines

Prosthetic graft infection is most commonly due to Gram-positive cocci (option A). These infections typically involve Staphylococcus species, particularly Staphylococcus aureus and coagulase-negative staphylococci like Staphylococcus epidermidis, as reported in a study published in Circulation 1. The ability of these organisms to adhere to prosthetic materials and form biofilms protects them from host defenses and antibiotics, making treatment challenging. Key points to consider in the management of prosthetic graft infections include:

• Early graft infections (within 4 months of implantation) are often due to S. aureus
• Late infections frequently involve coagulase-negative staphylococci
• Management typically requires a combination of surgical intervention and prolonged antibiotic therapy tailored to culture results
• Prevention strategies include perioperative antibiotics, strict aseptic technique during implantation, and careful skin preparation A more recent study published in Cardiovascular Research in 2023 1 also highlights the diversity of pathogens involved in prosthetic valve endocarditis, but still identifies staphylococci, including S. aureus, as common causes. Given the high morbidity and mortality associated with these infections, prompt and effective treatment is crucial to improve patient outcomes, and should be guided by the most recent and highest quality evidence available, such as the study by 1.

From the Research

Prosthetic Graft Infection Organisms

• The most common organisms causing prosthetic graft infection are:
  • Gram-positive cocci, specifically Staphylococci, such as Staphylococcus epidermidis and Staphylococcus aureus 2, 3, 4, 5
  • Gram-negative rods are also likely to be isolated, but less common than Gram-positive cocci 2
• The prevalence of Gram-positive cocci as the infecting organisms in prosthetic graft infections is reported to be:
  • 59% of isolates in intracavitary graft infections 3
  • 76% of isolates in extracavitary graft infections 3
• Staphylococcus epidermidis is a common infecting organism, accounting for 40% of patients with prosthetic graft infections 3

Treatment and Management

• The treatment of prosthetic graft infections often involves a combination of surgical and antimicrobial approaches 2, 3, 6
• Empirical treatment may include a penicillinase-resistant beta-lactam or a glycopeptide, plus an aminoglycoside for Gram-negative coverage and synergistic treatment of Gram-positive cocci 2
• In situ replacement with a rifampin-bonded graft or autogenous vein replacement may be effective for certain types of prosthetic graft infections, such as those caused by Staphylococcus epidermidis 3