Molecular fingerprinting of multidrug-resistant Mycobacterium tuberculosis strains in Beirut reveals genetic diversity and father to daughter transmission.

The typing of six consecutive multidrug-resistant Mycobacterium tuberculosis strains isolated from patients with tuberculosis (TB) at the American University of Beirut Medical Center, was performed by touchdown double-repetitive-element (DRE)-PCR. The isolates exhibited four distinct patterns in DRE-PCR with three isolates exhibiting unique patterns and three isolates yielded similar DNA fragment patterns (cluster pattern). Only two of the three cluster isolates exhibited identical patterns as revealed by restriction fragment length polymorphism (RFLP) targeting specific mutations in the rpoB and katG genes that confer resistance to rifampin and isoniazid, respectively. A direct epidemiological linkage for the two isolates exhibiting genotypic relatedness was also established as the isolates were recovered from a 33-year-old man and his 8-year-old daughter. The data show that transmission of multidrug-resistant M. tuberculosis strains is contributing to the emergence of drug-resistant TB in Beirut. Combining DRE-PCR with RFLP at the rpoB and katG genes could provide a powerful means for investigating the spread of multidrug-resistant M. tuberculosis strains in Lebanon.