In a male patient with type 2 diabetes mellitus and a persistent psoas abscess, Staphylococcus aureus susceptible to teicoplanin has been treated for 15 days but drainage continues, and pus CBNAAT (cartridge‑based nucleic acid amplification test) shows rifampicin‑resistant Mycobacterium tuberculosis; what evaluation and tuberculosis treatment protocol should be followed?

Management of Rifampicin-Resistant TB in a Diabetic Patient with Persistent Psoas Abscess

This patient requires immediate initiation of a multidrug-resistant TB (MDR-TB) treatment regimen with at least five effective drugs while continuing drainage of the psoas abscess, and you must obtain comprehensive drug susceptibility testing for both first- and second-line anti-TB drugs immediately. 1, 2

Immediate Actions Required

1. Microbiological Confirmation and Drug Susceptibility Testing

• Send the current pus specimen immediately to a reference laboratory for comprehensive drug susceptibility testing (DST) to both first-line and second-line anti-TB drugs 1, 3
• Continue collecting specimens for culture and DST while initiating empirical treatment—never modify treatment without obtaining samples as this eliminates the opportunity to identify the complete resistance pattern 3, 4
• The CBNAAT showing rifampicin resistance strongly suggests MDR-TB (resistance to at least isoniazid and rifampicin), but phenotypic DST is essential to confirm the full resistance profile 1, 4

2. Continue Adequate Source Control

• Maintain continuous drainage of the psoas abscess as persistent pus drainage after 15 days indicates inadequate source control, which will prevent cure regardless of antibiotic choice 5, 6
• Consider surgical consultation if percutaneous drainage continues to fail—open surgical drainage via extraperitoneal approach may be necessary 5
• The combination of Staphylococcus aureus and Mycobacterium tuberculosis in a psoas abscess has been documented and requires treatment of both organisms 6

3. Continue Staphylococcal Coverage

• Continue teicoplanin for the Staphylococcus aureus component at appropriate dosing (6 mg/kg every 12 hours for 3 doses, then daily) until adequate source control is achieved and clinical improvement occurs 7, 8, 9
• Diabetes increases risk of treatment failure for both bacterial and mycobacterial infections, requiring vigilant monitoring 5

MDR-TB Treatment Protocol

Empirical Regimen Composition (While Awaiting Full DST)

Initiate treatment with at least five effective drugs immediately using the WHO classification system 1:

Core Regimen Components:

Group A (Fluoroquinolone) - Choose ONE:

• Levofloxacin OR
• Moxifloxacin OR
• Gatifloxacin 1

Group B (Injectable Agent) - Choose ONE:

• Amikacin (preferred) OR
• Capreomycin OR
• Kanamycin 1

Group C (Core Second-Line Agents) - Choose at least TWO:

• Linezolid
• Cycloserine/Terizidone
• Ethionamide/Prothionamide
• Clofazimine 1

Group D (Add-on Agents):

• Pyrazinamide (if susceptible)
• Ethambutol (if susceptible)
• Consider Bedaquiline or Delamanid if available 1

Critical Treatment Principles

• NEVER add a single drug to a failing regimen—this creates resistance to the new drug and further complicates management 1
• Do not use any drug to which documented resistance exists (either by molecular or phenotypic DST) 1
• All drugs must be administered via directly observed therapy (DOT) 2, 3

Treatment Duration

• Minimum 20 months of treatment with at least five effective drugs 1
• Intensive phase should last at least 8 months 1
• If the patient meets eligibility criteria for the shorter MDR-TB regimen (9-11 months), this can be considered, but only after full DST results confirm eligibility 1

Special Considerations for This Patient

Diabetes Management

• Tight glycemic control is essential as diabetes significantly impairs immune response and increases risk of treatment failure 5
• Monitor for drug interactions between anti-TB medications and diabetes medications
• Fluoroquinolones can cause dysglycemia—monitor blood glucose closely 1

Monitoring Requirements

• Monthly clinical evaluations to assess adherence and identify adverse drug effects 1, 2
• Monthly sputum/pus cultures until two consecutive specimens are negative 1, 2
• Baseline and periodic monitoring of hepatic function, renal function, complete blood count, and electrolytes 1
• Visual acuity and color discrimination testing if ethambutol is used 1
• Audiometry and renal function monitoring if injectable agents are used 1
• ECG monitoring if fluoroquinolones, bedaquiline, or clofazimine are used 1

HIV Testing

• All TB patients should receive HIV counseling and testing 1
• If HIV-positive with CD4 <100 cells/μL, daily therapy is required during both intensive and continuation phases 2

Adjusting Treatment Based on DST Results

Once comprehensive DST results return:

• Immediately adjust the regimen according to the confirmed resistance pattern 3, 4
• Ensure at least five drugs with confirmed or highly probable susceptibility are maintained 1
• If fewer than five effective drugs can be composed from Groups A-C, add agents from Groups D2 and D3 1

Consultation Requirement

Immediate consultation with an MDR-TB expert or specialized treatment center is mandatory 1, 2. Treatment of rifampicin-resistant/MDR-TB represents the patient's last best chance for cure, and inappropriate management has life-threatening consequences 1.

Common Pitfalls to Avoid

• Do not delay MDR-TB treatment while waiting for full DST results—rifampicin resistance detected by CBNAAT is sufficient to initiate empirical MDR-TB therapy 1, 3
• Do not continue standard first-line TB drugs alone once rifampicin resistance is confirmed 1
• Do not neglect adequate source control—antimicrobials alone will not cure a persistent abscess requiring drainage 5, 6
• Do not assume the Staph aureus is the only pathogen—the TB must be treated aggressively as the primary pathogen 6