Genotypic assessment of Drug Resistant Tuberculosis in Baghdad and other Iraqi provinces using low-cost and density (LCD) DNA microarrays

We report on a molecular investigation carried out to ascertain the prevalence of drug resistant TB and the specific gene mutations responsible for resistance to rifampicin (RIF) and/or isoniazid (INH) in Iraq. One hundred and ten clinical isolates from category II TB cases from Baghdad (58%) and several Iraqi provinces (42%) were analyzed using colorimetric, low-cost and density (LCD) microarrays (MYCODirect and MYCOResist LCD-array kits, Chipron GmbH, Germany) to identify the point mutations responsible for resistance in Mycobacterium tuberculosis isolates. Seventy-six patients (69.1%) had resistant strains, of which 40 (36%) were MDRTB. 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 MDRTB 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 MYCOResist LCD-array and GenoType MTBDRplus for detection of resistance to RIF. Our study shows MDRTB in 36% of category II TB cases in Baghdad and surrounding Iraqi provinces which reflects World Health Organization (WHO) findings based on phenotypic studies. Diagnosis of TB and MDR-TB using culture-based tests are 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.