Drug sensitivity patterns in Xpert-positive spinal tuberculosis: an observational study of 252 patients.

PURPOSE: To evaluate the sensitivity patterns of anti-tubercular drugs in Xpert MTB-positive spinal tuberculosis (TB) patients and to formulate the guidelines for early start of empiric anti-tubercular treatment (ATT) in MDR-TB spine based on resistance pattern in this large series. METHODS: It was a cross-sectional observational study of 252 consecutive patients who were Xpert MTB-proven spinal TB cases with retrospective analysis of prospective data. The Xpert MTB/RIF (Mycobacterium tuberculosis/rifampicin) assay was used to diagnose spinal TB and RIF resistance. All patients underwent drug sensitivity testing (DST) to 13 commonly used anti-tubercular drugs using BACTEC MGIT-960 system. The drug sensitivity pattern of primary and secondary anti-tubercular drugs was recorded and compared. RESULTS: The DST study revealed 110 (43.6%) cases of multi-drug resistant (MDR-resistance to both isoniazid and rifampicin) and 24 (9.5%) cases of non-MDR-TB spine. The widespread resistance was found for both isoniazid (91%) and rifampicin (85%), followed by streptomycin (61.9%). The least resistance was found for kanamycin, amikacin and capreomycin and no resistance found for clofazimine. CONCLUSION: The Xpert MTB/RIF assay is an efficient technique for the rapid diagnosis of spinal TB and suspected MDR-TB; however, it is recommended to do culture and DST in all patients with spinal TB to guide the selection of appropriate second-line drugs when required. In cases of non-availability of culture and DST, it is suggested to use data from large series such as this to plan the best empirical ATT regimen. These slides can be retrieved under Electronic Supplementary Material.