rpoB gene mutations among Mycobacterium tuberculosis isolates from extrapulmonary sites

Area of Science:

• Microbiology
• Genetics
• Infectious Diseases

Background:

• Extrapulmonary tuberculosis (EPTB) poses diagnostic challenges.
• Understanding drug resistance mechanisms in Mycobacterium tuberculosis (MTB) is crucial for effective treatment.

Purpose of the Study:

• To investigate mutations in the rpoB gene of MTB isolates from EPTB clinical samples.
• To identify common mutation sites associated with rifampin resistance in EPTB.

Main Methods:

• Analysis of formalin-fixed, paraffin-embedded and fresh tissue samples from EPTB cases.
• Nested PCR amplification of the rpoB gene, followed by cloning and sequencing.
• Sequence analysis of the 81 bp region of the rpoB gene.

Main Results:

• 67 out of 70 (95.7%) samples were positive by nested PCR.
• Mutations in the rpoB gene were detected in 41 out of 67 (61.2%) sequenced samples.
• Codon 513 alterations (Gln → His) were the most common mutation (75.6%), strongly associated with rifampin resistance.

Conclusions:

• Sequence alterations in codon 513 of the rpoB gene are the predominant mutation in rifampin-resistant MTB strains from EPTB.
• Simultaneous mutations at codons 512 and 513 were observed in 34.3% of isolates.
• The findings highlight the importance of rpoB gene sequencing for diagnosing rifampin resistance in EPTB.