A70-29 When the Drug Is Not on the Shelf: The Challenge of Treating Multidrug-resistant Tuberculosis (MDR-TB) in Puerto Rico

Abstract Introduction Multidrug-resistant tuberculosis (MDR-TB), defined as resistance to at least isoniazid and rifampin, remains a major global health threat. According to the World Health Organization (WHO) Global Tuberculosis Report 2024, an estimated 410,000 people worldwide developed multidrug-resistant or rifampin-resistant tuberculosis (MDR/RR-TB) in 2023, representing 3% of all new and 18% of previously treated cases. In America, MDR-TB affects fewer than 3% of new cases, and in Puerto Rico, incidence is estimated at < 0.5 per 100,000 population. Despite its rarity, MDR-TB poses disproportionate challenges in U.S. territories where molecular diagnostic capacity, drug availability, and access to preferred regimens remain limited. This case highlights the diagnostic, therapeutic, and economic barriers to managing Centers for Disease Control and Prevention (CDC)-confirmed MDR-TB in a resource-limited setting. Case Description A 65-year-old Puerto Rican man presented with six months of productive cough, dyspnea, night sweats, and weight loss. Evaluation revealed a positive tuberculin skin test, a 3+ acid-fast bacilli (AFB) sputum smear, and polymerase chain reaction (PCR)-confirmed rifampin-resistant tuberculosis (RR-TB). Chest computed tomography (CT) demonstrated bilateral miliary nodules and a left upper-lobe cavitary lesion consistent with active TB. Empiric first-line therapy with isoniazid, pyrazinamide, ethambutol, and levofloxacin was initiated under directly observed therapy. Despite adherence, sputum smears remained 3+ positive after four weeks. CDC Molecular Detection of Drug Resistance (MDDR) testing confirmed resistance to rifampin, isoniazid, and ethambutol, establishing MDR-TB. Per WHO and Infectious Diseases Society of America (IDSA) guidelines, optimal MDR-TB therapy includes the BPaLM regimen (bedaquiline, pretomanid, linezolid, and moxifloxacin). However, bedaquiline and pretomanid were unavailable locally, and access required interstate coordination through the Puerto Rico Department of Health and the CDC, delaying optimal therapy. The regimen was modified to linezolid, moxifloxacin, and pyrazinamide under CDC guidance. The patient remains hospitalized after ten weeks in prolonged isolation with persistently positive AFB smears, resulting in significant healthcare and resource expenditures. Conclusion This case underscores the clinical and logistical barriers to managing MDR-TB in low-incidence regions. Clinicians faced the dilemma of initiating guided therapy without access to the WHO-preferred BPaLM regimen, as critical drugs required multi-agency authorization. These delays prolong infectivity, heighten resistance risk, and strain public-health systems. Extended inpatient isolation creates a major economic burden, with costs estimated at six times those of drug-susceptible TB. Expanding local molecular testing, ensuring regional access to bedaquiline and pretomanid, and improving inter-agency coordination are essential to reduce the clinical, economic, and systemic impact of MDR-TB. This abstract is funded by: None