Discordant rifampicin-resistance results in a newly treated pulmonary tuberculosis case: a diagnostic challenge from Khyber Pakhtunkhwa

Abstract

We reveal the situation of a 56-year-old male from Mardan who first presented to the hospital in 2023 with a two-month history of cough with sputum. He was diagnosed using Xpert MTB/RIF (MTB positive, RIF resistance not detected), placed on first-line tuberculosis (TB) treatment, and declared treatment completed after 6 months. Only 2-3 weeks later, he returned with the same symptoms. A repeat Xpert test showed scanty MTB with RIF resistance, and culture identified rifampicin-resistant Mycobacterium tuberculosis (MTB). Subsequent work-up showed Xpert MTB/RIF positive, with RIF resistance not detected. However, Xpert XDR suggested fluoroquinolone resistance. The culture, initially contaminated, later revealed fully drug-sensitive MTB. This case underscores the complexities of interpreting inconsistent molecular and phenotypic results in TB drug-resistance diagnostics. It highlights the limitations of Xpert in low-bacillary-load specimens and the need to combine microbiological, molecular, and clinical findings when handling presumed MDR/XDR-TB cases.