Infectious DiseasesTier 1Disease (DEADMAN)

Bacteraemia

Description

Presence of viable bacteria in the bloodstream, confirmed by positive blood culture
Spectrum from transient/incidental to sustained bacteraemia with sepsis - the organism identified determines the required work-up, not just the fact of a positive culture

Commonest sources: urinary tract, respiratory tract, intra-abdominal, skin/soft tissue, line-associated
Staphylococcus aureus bacteraemia (SAB) - disproportionately high morbidity/mortality (~20-30% mortality) relative to other organisms, deserves distinct management pathway
Gram-negative bacteraemia (E. coli commonest) usually urinary/abdominal source, generally better prognosis if source controlled

By likely source and organism

Urinary: E. coli, Klebsiella, Proteus
Intra-abdominal: polymicrobial - Enterobacteriaceae, anaerobes, Enterococcus
Skin/soft tissue: Staphylococcus aureus, Streptococcus pyogenes
Line-associated: coagulase-negative staphylococci (commonest contaminant and true pathogen), S. aureus, Candida
Endocarditis-prone organisms: S. aureus, viridans streptococci, Enterococcus - always consider endocarditis when these are found without an obvious alternative source

A. Confirm true bacteraemia vs contaminant

Coagulase-negative staphylococci in a single bottle - often a contaminant, but treat as true if multiple positive sets, clinical sepsis, or a prosthetic device present
Repeat cultures to confirm clearance, especially in S. aureus bacteraemia

B. Source identification - essential in every case

Full clinical assessment, imaging directed by likely source
Echocardiography (start with TTE, proceed to TOE if high suspicion/inconclusive) for S. aureus, viridans streptococci, or Enterococcus bacteraemia - to exclude infective endocarditis

C. Staphylococcus aureus bacteraemia - a distinct, high-stakes work-up

Repeat blood cultures at 48-72h to document clearance - persistent positivity signals a deep/undrained focus
Echocardiography in all (see above)
Examine for metastatic seeding - spine (discitis/epidural abscess if back pain), joints, other deep sites
Remove/exchange any infected line or prosthetic material where feasible - critical for source control

A. Empirical therapy

Guided by likely source and local antibiogram while awaiting speciation/sensitivities
Narrow to targeted therapy once organism and sensitivities known

B. Staphylococcus aureus bacteraemia - specific principles

MSSA: flucloxacillin or cefazolin - narrow-spectrum beta-lactams outperform vancomycin for MSSA, use vancomycin only if genuinely penicillin-allergic
MRSA: vancomycin (target trough per local protocol) or daptomycin
Minimum 14 days IV therapy for uncomplicated SAB (clear source control, no endocarditis/metastatic focus, cultures clear by 48-72h, defervescence); 4-6 weeks for complicated SAB (endocarditis, undrained focus, prosthetic material, persistent bacteraemia)
Infectious diseases consultation improves outcomes in SAB and should occur for every case

C. Gram-negative bacteraemia

Typically shorter courses (7 days for uncomplicated, source-controlled bacteraemia per recent evidence) once clinically stable and source controlled
De-escalate from broad empirical cover once sensitivities return

D. Source control - non-negotiable regardless of organism

S. aureus bacteraemia: high risk of metastatic seeding (endocarditis, discitis, septic arthritis, abscesses) if inadequately treated - relapse common with inadequate duration or missed source
Gram-negative bacteraemia - generally better prognosis with source control and appropriate duration
Persistent bacteraemia despite therapy - always implies an uncontrolled source (endocarditis, undrained collection, infected device) requiring active search, not simply longer antibiotics

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