Concomitant methicillin-resistant Staphylococcus aureus infection in tubercular sacroiliitis masquerading as anti-tubercular drug resistance: Role for molecular diagnosis.

A 23-year-old female on anti-tubercular therapy for tuberculous sacroiliitis presented with right sided gluteal and thigh abscess. Suspecting treatment failure, surgical evacuation of purulent material was done. The bacteriological isolation showed positivity for methicillin-resistant Staphylococcus aureus. Although the microbiological and histopathology examination of the specimen were negative for tubercular isolates, the cartridge based -nucleic acid amplification tests revealed positive genes for Mycobacterium tuberculosis and additional primers showed sensitivity for rifampicin and isoniazid. She was adequately treated with vancomycin for six weeks and anti-tubercular drugs for eight months and followed till the bony ankyloses at 18 months. This is a rare case based scenario wherein concomitant staphylococcal infection in tubercular sacroiliitis masqueraded as anti-tubercular drug resistance. The cartridge-based nucleic acid amplification test for tuberculosis is a rapid and sensitive modality in identifying mycobacteria even mixed infections and also determine drug resistance. There are fewer consensuses in the literature regarding the drugs and duration of anti-tubercular regime for tuberculous sacroiliitis with most regimes using four drugs between six to eighteen months.