DISTRIBUTION OF RIFAMPICIN- AND ISONIAZID RESISTANCE-ASSOCIATED MUTATIONS IN PEDIATRIC MULTIDRUG-RESISTANT TUBERCULOSIS IN KHYBER PAKHTUNKHWA

Abstract

Background: Multidrug-resistant tuberculosis (MDR-TB) remains a major challenge in children, and the molecular patterns underlying rifampicin (RIF) and isoniazid (INH) resistance may vary geographically. Data on resistance-associated mutations among pediatric MDR-TB patients in Khyber Pakhtunkhwa (KP), Pakistan, remain limited. Objective: To determine the frequency and distribution of RIF- and INH-resistance-associated mutation patterns, including individual and combined mutations in the rpoB, katG, and inhA genes, among pediatric patients with MDR-TB in KP, Pakistan. Methodology: This study included 266 pediatric MDR-TB patients. Drug resistance-associated mutation patterns were assessed using the GenoType MTBDRplus line probe assay. The assay was used to identify mutations and wild-type probe patterns within the rpoB, katG, and inhA regions. Individual and combined mutation patterns were summarized using frequencies and percentages, and molecular findings were compared with phenotypic drug susceptibility testing results. Results: RIF resistance was detected by LPA in 211 (79.32%) isolates, while INH resistance was detected in 225 (84.58%). Among RIF-resistant isolates, 113 (53.55%) showed loss of one or more rpoB wild-type probes without a corresponding detectable mutant probe, consistent with an uncharacterized resistance-associated change within the targeted region. Among the 98 isolates with identifiable rpoB mutant patterns, S531L was the most frequent single mutation (37.75%), followed by D516V (19.39%) and H526D (7.14%). Combined mutations included D516V+S531L (7.14%) and H526D+S531L (3.06%). For INH resistance, katG-associated patterns were more frequent than inhA-associated patterns. Conclusion: Pediatric MDR-TB in KP demonstrates diverse RIF and INH-resistance-associated mutation patterns, with rpoB S531L and katG-associated resistance being prominent. The substantial proportion of unresolved LPA patterns highlights the need for sequencing-based studies to characterize unrecognized resistance associated mutations.