Genotypic assessment of drug-resistant tuberculosis in Baghdad and other Iraqi provinces using low-cost and low-density DNA microarrays

J Med Microbiol. 2016 Feb;65(2):114-122. doi: 10.1099/jmm.0.000203. Epub 2015 Nov 10.

Abstract

We report on a molecular investigation carried out to ascertain the prevalence of drug-resistant tuberculosis (TB) and the specific gene mutations responsible for resistance to rifampicin (RIF) and/or isoniazid (INH) in Iraq. In total, 110 clinical isolates from category II TB cases from Baghdad (58%) and several Iraqi provinces (42%) were analysed using colorimetric, low-cost and low-density (LCD) microarrays (MYCO-Direct and MYCO-Resist LCD array kits) to identify the point mutations responsible for resistance in Mycobacterium tuberculosis isolates. We found 76 patients (69.1%) had resistant strains, of which 40 (36%) were multidrug-resistant (MDR)-TB. Where mono-resistance was identified, it was found to be predominantly to RIF (83%). The most common mutations were rpoB S531L (50%), inhA C15T (25%) and katG S315T (15%). The most common MDR-TB genotypes were rpoB S531L with inhA C15T (60%) and rpoB S531L with katG S315T (20%). Where phenotypic analysis of clinical isolates was also performed, genotypic data were found to show excellent correlation with phenotypic results. Correlation was found between the MYCO-Resist LCD array and GenoType MTBDRplus for detection of resistance to RIF. Our study shows MDR-TB in 36% of category II TB cases in Baghdad and surrounding Iraqi provinces, which reflects the World Health Organization findings based on phenotypic studies. Diagnosis of TB and MDR-TB using culture-based tests is a significant impediment to global TB control. The LCD arrays investigated herein are easy to use, sensitive and specific molecular tools for TB resistance profiling in resource-limited laboratory settings.

MeSH terms

  • Adolescent
  • Adult
  • Antitubercular Agents / pharmacology*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Catalase / genetics
  • Catalase / metabolism
  • Child
  • Drug Resistance, Multiple, Bacterial*
  • Female
  • Genotype
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Mycobacterium tuberculosis / classification
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / genetics*
  • Mycobacterium tuberculosis / isolation & purification*
  • Oligonucleotide Array Sequence Analysis / economics
  • Oligonucleotide Array Sequence Analysis / methods*
  • Sputum / microbiology
  • Tuberculosis, Multidrug-Resistant / microbiology*
  • Young Adult

Substances

  • Antitubercular Agents
  • Bacterial Proteins
  • Catalase