Infectious DiseasesTier 1Disease (DEADMAN)

Line and prosthetic infections

Description

Infection of an indwelling vascular catheter (CLABSI) or implanted prosthetic material (joint, valve, graft, pacemaker/ICD)
Unifying feature: biofilm formation on foreign material protects organisms from antibiotics and host defence - drives the need for device removal in most cases

CLABSI risk rises with catheter dwell time, number of lumens, and insertion site (femoral > internal jugular > subclavian)
Prosthetic joint infection - ~1-2% of primary arthroplasties, higher in revision surgery
Prosthetic valve endocarditis - ~1-6% lifetime risk post-valve replacement, higher risk in the first year

Mechanism

Organisms adhere to foreign material -> biofilm formation -> reduced antibiotic penetration and immune clearance -> chronic/relapsing infection unless the material is removed

Organisms by device and timing

Coagulase-negative staphylococci - commonest overall for lines and early prosthetic infection (indolent, biofilm-forming)
Staphylococcus aureus - commonest cause of severe/acute line infection and early prosthetic joint infection; high metastatic seeding risk
Gram-negative bacilli, Candida - especially in immunosuppressed, prolonged line dwell, or TPN
Late prosthetic joint infection: often haematogenous seeding from a distant infection (dental, skin, urinary)
Prosthetic valve endocarditis: early (<1 year, typically staphylococci/perioperative contamination) vs late (>1 year, organism profile resembles native valve endocarditis)

Line infection

Fever +/- exit-site erythema/purulence; differential time to positivity (DTP) - paired peripheral and catheter-drawn cultures, catheter culture turning positive >=2 hours earlier supports catheter as the source
Catheter tip culture (semi-quantitative) if line removed

Prosthetic joint infection

Persistent pain, effusion, sinus tract, or early wound complications (early infection) vs subtle chronic pain/loosening (late/chronic infection)
Joint aspiration - synovial WCC, culture (hold antibiotics before sampling if possible), synovial alpha-defensin/leukocyte esterase adjuncts
Multiple intra-operative tissue cultures (not just one) improve diagnostic yield
Inflammatory markers (ESR/CRP) supportive but non-specific, especially soon after surgery

Prosthetic valve endocarditis

Modified Duke criteria (as for native valve, adjusted for prosthetic material); TOE preferred over TTE given lower sensitivity of TTE for prosthetic valve vegetations/abscess
Blood cultures before antibiotics - essential for organism-directed therapy

A. General principle across all device infections

Source control (device removal/exchange) plus antibiotics - antibiotics alone rarely cure biofilm-associated infection

B. Line infections

Remove the line for: S. aureus, Candida, severe sepsis/shock, persistent bacteraemia despite therapy, tunnel/pocket infection, or septic thrombophlebitis
Salvage with antibiotic lock therapy + systemic antibiotics may be attempted for coagulase-negative staphylococcal infection in a difficult-to-replace line (e.g. tunnelled dialysis catheter) if clinically stable
Duration: short course (e.g. 5-7 days) if line removed and prompt clearance for uncomplicated coagulase-negative staph; longer (2-6 weeks) for S. aureus, Candida, or complicated infection (endocarditis, septic thrombosis, metastatic seeding)

C. Prosthetic joint infection

Early infection (<3 months) with a stable implant: debridement, antibiotics and implant retention (DAIR) + prolonged antibiotics (often with rifampicin combination for staphylococcal biofilm penetration)
Chronic/late infection or unstable implant: one- or two-stage revision (removal of prosthesis, antibiotic spacer, staged reimplantation) - the definitive approach for established biofilm infection
Prolonged targeted antibiotic course (typically 6-12 weeks), often with oral step-down; infectious diseases and orthopaedic joint management

D. Prosthetic valve endocarditis

Longer antibiotic courses than native valve endocarditis (typically 6 weeks), often with combination therapy (e.g. rifampicin added for staphylococcal prosthetic valve infection, once bacteraemia controlled)
Early cardiac surgery referral - lower threshold than native valve disease given higher rates of heart failure, abscess, and valve dehiscence

E. Prevention

Aseptic insertion technique, minimise line dwell time, remove lines as soon as no longer needed, antibiotic prophylaxis for at-risk dental/surgical procedures per current cardiac society guidance in prosthetic valve patients

Persistent bacteraemia/failure to defervesce despite appropriate antibiotics strongly implies retained infected material requiring removal
Untreated/undertreated prosthetic joint infection - progressive bone loss, chronic sinus tract, need for salvage arthrodesis or amputation in severe cases
Prosthetic valve endocarditis carries higher mortality than native valve disease, particularly with paravalvular abscess or dehiscence
Relapse common if device not removed when indicated, regardless of antibiotic duration

6 more sections, plus exam facts

Premium unlocks every note across every specialty, and the full exam fact library behind it.