Annotations only — chart still shows the full chemistry of each drug.
1. Clinical Syndrome
Infection of vertebral body, intervertebral disc, and/or adjacent paraspinal soft tissue. Classic presentation: subacute / chronic back pain (weeks to months), fever in <50%, elevated ESR/CRP. Lumbar > thoracic > cervical.
Routes: hematogenous (most common — bacteremia from skin, GU, IV access), contiguous (post-procedural), direct inoculation (penetrating trauma, surgery).
Excludes: post-operative / hardware-associated spinal infection (separate workflow — analogous to PJI with rifampin combos), tuberculous (Pott's) and brucellar spondylitis (chronic, dedicated workups), disc-space-only infection without vertebral involvement, epidural abscess without bone involvement (overlapping but distinct — usually surgical emergency).
2. Pathogens
Consider the patient: Age (older more common), comorbidities (diabetes, CKD/dialysis access, IVDU, immunocompromise), recent bacteremia or distant infection (skin, GU, line), recent spinal procedure or epidural.
Consider the case: Acute (S. aureus, GNR) vs subacute/chronic (consider TB, Brucella, fungi). Risk factors for MRSA → empiric vanc. IVDU → Pseudomonas risk. Healthcare-associated bacteremia precedent — match empirics to known source.
Common
- Staphylococcus aureus (MSSA)
**Most common pathogen overall (~50%)** — community + healthcare-associated bacteremia source.
- Staphylococcus aureus (MRSA)
Healthcare-associated, prior MRSA, IVDU — empiric vanc when risk factors present.
- Escherichia coli
Hematogenous seeding from UTI source — older patients especially.
- Coagulase-Negative Staphylococci
Post-operative / hardware-associated. Multiple positive cultures + clinical correlate before treating.
- Staphylococcus aureus (MSSA)
Less common
- Streptococcus pyogenes (Group A Strep)
Skin / soft tissue bacteremia source.
- Viridans Group Streptococci
Endocarditis-associated bacteremia — get TTE/TEE.
- Pseudomonas aeruginosa
IVDU, healthcare-associated, immunocompromised.
- Enterococcus faecalis
GU source, post-instrumentation.
- Candida albicans
Hematogenous seeding from candidemia — esp TPN, recent abdominal surgery, prolonged broad abx.
- Streptococcus pyogenes (Group A Strep)
3. Empiric Therapy
| Tier | First choice | Alternatives | Duration | Comments |
|---|---|---|---|---|
| Admitted to ward |
|
| **6 weeks minimum** total therapy (IDSA 2015). PO step-down after 2 weeks IV reasonable when stable + susceptible organism + bioavailable PO option. | **Empiric while awaiting cultures.** Get **blood cultures × 2 sets + biopsy/aspirate** before antibiotics whenever possible — diagnosis depends on tissue. If patient stable and neurologically intact, **HOLD antibiotics until biopsy** (improves yield substantially). Vanc covers MRSA; CTX covers MSSA + GNR + most strep. |
| ICU — Pseudomonas risk |
|
| 6 weeks minimum total; extend if hardware retained or slow response | **Sepsis / IVDU / immunocompromise / healthcare-associated.** Covers MRSA + Pseudomonas + Enterobacterales empirically. Neurosurgical consult if cord compression or epidural abscess on MRI. |
Add coverage if:
- Known MRSA colonization
- Healthcare exposure
- IVDU
- Severe disease
Add:
- load + AUC-guided · — · IV
- IVDU
- Healthcare-associated
- Immunocompromised
- Prior Pseudomonas isolate
Add:
- 2 g · q8h · IV
Or pip-tazo / meropenem.
- Concurrent candidemia
- Hematogenous source from TPN line
- Recent broad-spectrum abx
Add:
- 400–800 mg · daily · IV/PO
Step down from echinocandin once C. albicans susceptible. 6 weeks minimum.
4. Directed Therapy
Get tissue before antibiotics. Image-guided biopsy / aspiration ± blood cultures. Yield is dramatically higher if antibiotics held >48 h pre-biopsy.
Once organism identified — 6 weeks minimum, IV preferred for first 2 weeks at least:
- MSSA: cefazolin 2 g IV q8h × 6 weeks (preferred over nafcillin — equivalent efficacy, better tolerated, easier OPAT).
- MRSA: vancomycin AUC-guided × 6 weeks. Daptomycin 6 mg/kg if vanc intolerance (good bone penetration).
- Streptococcus (PCN-S): PCN-G 4 MU IV q4h × 6 weeks, or ceftriaxone 2 g daily for OPAT.
- Enterococcus faecalis: ampicillin 2 g q4h ± aminoglycoside × 6 weeks.
- Enterobacterales: ceftriaxone or FQ × 6 weeks based on susceptibility.
- Pseudomonas: anti-pseudomonal β-lactam × 6 weeks; combo with FQ/aminoglycoside early in severe disease.
- Candida: fluconazole if susceptible × 6 weeks; echinocandin × 2 weeks then PO step-down acceptable.
Concurrent infection / source: rule out endocarditis (TTE / TEE in S. aureus, strep, enterococcus); rule out epidural abscess (MRI with contrast); rule out psoas abscess.
Surgical indications: neurologic compromise, instability, large epidural / paraspinal abscess refractory to drainage, failure of medical therapy.
Outpatient / chronic suppression: oral step-down after 2+ weeks IV when (1) organism susceptible to bioavailable oral agent, (2) clinical improvement, (3) reliable adherence. Options: levofloxacin + rifampin (staphylococci), linezolid, TMP-SMX. OVIVA trial 2019 demonstrates oral step-down non-inferior to 6 weeks IV for bone & joint infection.
5. Monitoring
Resolution: pain, fever, ESR/CRP trend (CRP normalizes by ~4 weeks, ESR slowest). Clinical improvement is the primary metric — imaging changes lag.
Repeat MRI at 4–6 weeks if pain persists or clinical worsening — looking for abscess, instability, failed source control.
Toxicity: vanc AUC + Cr q48h; cefepime mental status; FQ tendinopathy / QT / dysglycemia; OPAT line surveillance.
Pearls
Hold antibiotics before biopsy when feasible — single most modifiable factor for improving microbiologic yield. S. aureus dominates — empirics should cover. 6 weeks is the standard duration (IDSA 2015); shorter courses fail. Endocarditis workup is mandatory for S. aureus / strep / enterococcus VO — TTE first, TEE if high-risk or TTE negative. OVIVA trial 2019: oral step-down after 2 weeks is non-inferior to 6 weeks IV for bone/joint infection — but only with reliable PO agent + adherence. Concurrent epidural abscess + neurologic findings = surgical emergency.