Genotypic Diversity among Isoniazid-Resistant Isolates of Mycobacterium tuberculosis from Rashid Hospital in Dubai, United Arab Emirates

Objective: To perform molecular fingerprinting for strain relatedness among isoniazid-resistant Mycobacterium tuberculosis isolates recovered from tuberculosis (TB) patients in the United Arab Emirates (UAE). Materials and Methods: Thirty-two consecutive isoniazid-resistant M. tuberculosis strains isolated from TB patients (4 natives and 28 expatriates) at Rashid Hospital, Dubai, UAE were analyzed. The typing was carried out by touchdown double-repetitive-element PCR (DRE-PCR). The status of R463 or L463 polymorphism and the presence of S315T mutation in the katG gene were also determined for isolates exhibiting cluster pattern in DRE-PCR. Results: All the 32 isolates (28 from expatriate patients and 4 from UAE nationals) exhibited 21 distinct patterns in DRE-PCR with 20 of 32 isolates exhibiting unique patterns and the remaining 12 exhibiting cluster ‘A’ pattern. All the isolates (19 of 19) yielding two or more DNA fragments in DRE-PCR were unique strains. The genotypic heterogeneity among 10 of the 12 cluster isolates was suggested by the varying susceptibility of these isolates to anti-TB drugs, presence of R463 or L463 polymorphism in thekatG gene and the presence or absence of S315T mutationin the katG gene. Conclusion: The genotypic diversityamong isoniazid-resistant M. tuberculosis isolatesmostly recovered from expatriate patients indicates thatmost expatriates were infected with a unique strainimported, most likely, from their country of origin andthat their latent infection was reactivated in UAE.