What's the best course of action for a 70-year-old patient with a history of pneumonia, sepsis, L3,4 discitis, and bilateral psoas abscess, who has not responded to multiple Antibiotics (AB) regimens and anti-tuberculosis (TB) treatment, despite a negative Interferon-Gamma Release Assay (IGRA) test?

Management of Refractory Discitis, Psoas Abscess, and Persistent Fever in a 70-Year-Old Patient

Your immediate priority is to obtain blood cultures from both the central venous line and peripheral sites, remove the central line with tip culture, and perform CT-guided or surgical drainage of the bilateral psoas abscesses while broadening antibiotic coverage to include MRSA and resistant gram-negative organisms. 1, 2

Differential Diagnosis for Persistent Fever

The most critical considerations in this clinical scenario include:

• Central line-associated bloodstream infection (CLABSI): The recently placed CV line is a high-risk source, particularly given the patient's immunocompromised state from prolonged illness and multiple antibiotic courses 1, 3
• Inadequately drained psoas abscess: Bilateral psoas abscesses require drainage for source control; antibiotics alone are insufficient for complex, loculated collections 1, 2, 4
• Resistant or atypical organisms: Multiple antibiotic regimens may have selected for resistant bacteria (MRSA, ESBL-producing organisms, or carbapenem-resistant Enterobacteriaceae) 5, 3
• Fungal infection: Prolonged broad-spectrum antibiotics, central line, and critical illness are risk factors for candidemia or invasive fungal infection 1
• Unrecognized endocarditis: Despite negative echo, consider repeat transesophageal echocardiography (TEE) as transthoracic echo has limited sensitivity 2
• Non-infectious causes: Malignancy, drug fever, or inflammatory conditions should be considered if infectious workup remains negative 1, 6

Immediate Diagnostic Steps

Obtain comprehensive cultures before any antibiotic changes:

• Blood cultures from the central line AND two peripheral sites to differentiate CLABSI from bacteremia 1, 3
• Remove the central venous catheter and send the tip for quantitative culture (>15 CFU suggests line infection) 1
• Repeat imaging (MRI or CT) to assess abscess size, loculation, and drainage feasibility 1, 2
• Consider repeat TEE rather than transthoracic echo, as initial studies may miss vegetations in 10-15% of cases 2
• Send fungal blood cultures (1,3-beta-D-glucan, galactomannan) given prolonged antibiotic exposure 1

Critical pitfall: Do not continue empiric anti-TB therapy with negative IGRA in an immunocompetent patient without microbiologic confirmation, as this delays appropriate treatment and adds toxicity 6

Source Control: Abscess Drainage

Bilateral psoas abscesses require drainage for cure; antibiotics alone have unacceptably high failure rates. 1, 2, 4

Drainage approach selection:

• CT-guided percutaneous drainage is the preferred initial approach for uniloculated abscesses >3 cm, with success rates of 80-90% when combined with antibiotics 1, 2
• Surgical drainage (open or retroperitoneoscopic) is indicated for: multiloculated abscesses, failed percutaneous drainage, or when spinal debridement is needed for discitis 1, 2, 4
• Send all drained fluid for aerobic, anaerobic, fungal, and mycobacterial cultures with sensitivities 2, 4

For L3-4 discitis: Assess for spinal instability or epidural extension that would require neurosurgical consultation for debridement and stabilization 4

Empiric Antibiotic Regimen Adjustment

Broaden coverage immediately while awaiting culture results:

Recommended regimen for refractory infection with recent central line:

• Vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mcg/mL) for MRSA and line-associated coagulase-negative staphylococci 1, 3
• PLUS Meropenem 1-2 g IV every 8 hours OR Piperacillin-tazobactam 4.5 g IV every 6 hours for resistant gram-negatives including Pseudomonas 5, 3
• Consider adding an aminoglycoside (amikacin 15 mg/kg IV daily) for synergy in severe sepsis, particularly if prior cultures showed gram-negative organisms 3

Alternative for carbapenem-resistant organisms (if prior cultures or high local resistance):

• Ceftazidime-avibactam 2.5 g IV every 8 hours has demonstrated success in refractory KPC-producing organisms with discitis and psoas abscess 5

Add empiric antifungal coverage if:

• Persistent fever >5 days on broad-spectrum antibiotics
• Central line in place >7 days
• Total parenteral nutrition or prolonged ICU stay
• Micafungin 100 mg IV daily or Caspofungin 70 mg loading dose, then 50 mg daily 1

Duration and Monitoring

Treatment duration for discitis and psoas abscess:

• Minimum 6 weeks of IV antibiotics for vertebral osteomyelitis/discitis, often requiring 8-12 weeks total 1, 4, 5
• Continue antibiotics for 2-3 weeks after normalization of inflammatory markers (CRP, ESR) 4
• Transition to oral antibiotics with high bioavailability (fluoroquinolones, linezolid) only after clinical improvement and negative repeat cultures 1, 4

Monitor response:

• Daily clinical assessment: fever curve, hemodynamic stability, mental status 1, 3
• CRP and ESR at baseline, then weekly (should decrease by 50% within 2 weeks of appropriate therapy) 6, 4
• Repeat blood cultures 48-72 hours after starting new antibiotics to document clearance 1, 3
• Repeat MRI at 4-6 weeks to assess abscess resolution and discitis healing 4

Critical Pitfalls to Avoid

• Do not continue ineffective antibiotics: Six weeks of multiple regimens without improvement indicates either inadequate source control or resistant organisms 6, 5
• Do not rely on negative IGRA alone to exclude TB: In elderly or immunocompromised patients, consider AFB cultures from abscess fluid, but do not continue empiric anti-TB therapy without microbiologic confirmation 6
• Do not delay central line removal: Each day a potentially infected line remains increases mortality risk by 10-15% 1
• Do not attempt antibiotic-only treatment for large psoas abscesses: Failure rates exceed 60% without drainage 1, 2, 4
• Do not underdose antibiotics in elderly patients: While renal adjustment is necessary, therapeutic drug monitoring (vancomycin troughs, aminoglycoside peaks/troughs) ensures adequate levels 3