The Presence and Copy Number of Insertion Sequence IS6110 in Mycobacterium tuberculosis Isolates from Pakistan

The insertion element IS6110 has been used extensively for the detection and strain differentiation of M. tuberculosis. The presence and copy number of IS6110 varies geographically. We have investigated the presence and copy number of this insertion sequence in M. tuberculosis isolates collected throughout Pakistan. All 92 confirmed cultures of M. tuberculosis from Pakistan were found to contain this insertion sequence when checked by PCR using primers based on IS6110 sequence. The copy number determined by the standard IS6110 restriction fragment length polymorphism varied from 2-18. Among 46 cultures used for copy number estimation 32 strains (69.5%) contained more than 10 copies of IS6110. The percentage of isolates having up to 5 copies of IS6110 was 6.25, while 21.7% isolates had copy number between 5 and 11. Our results confirmed the presence of IS6110 in all isolates of M. tuberculosis and showed that IS6110 is a useful marker for the detection and DNA fingerprinting of M. tuberculosis strains originating from Pakistan. (C) 2013 Friends Science Publishers