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Journal of Clinical Microbiology, May 2006, p. 1763-1768, Vol. 44, No. 5
0095-1137/06/$08.00+0 doi:10.1128/JCM.44.5.1763-1768.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Department of Pathology and Microbiology, The Aga Khan University, Karachi, Pakistan,1 Department of Bacteriology, Swedish Institute for Infectious Diseases Control, Stockholm, Sweden2
Received 20 June 2005/ Returned for modification 27 October 2005/ Accepted 10 March 2006
The estimated incidence of tuberculosis in Pakistan is 181 per 100,000; however, there is limited information on Mycobacterium tuberculosis genotypes circulating in the country. We studied 314 M. tuberculosis clinical isolates; of these, 197 (63%) isolates grouped into 22 different clusters, while 119 (37%) had unique spoligotypes. Eighty-nine percent of the isolates were pulmonary (Pul), and 11% were extrapulmonary (E-Pul). We identified Central Asian Strain (CAS), Beijing, T1, Latin American-Mediterranean, and East African-Indian genogroups. Beijing strains, reportedly the most prevalent spoligotype worldwide, constituted 6% of our strain population. The CAS1 strain comprised 121 (39%) of the study isolates. No difference was observed between clustered isolates from cases of Pul and E-Pul tuberculosis. However, E-Pul isolates included a greater number of unique spoligotypes than Pul isolates (P = 0.005). The overall percentage of drug resistance was 54%, and that of MDR strains was 40%. While CAS1 strains were not associated with drug resistance, the relative risk of MDR was significant in Beijing strains compared to the non-Beijing groups (95% confidence interval, 1.2 to 8.9). The fact that the predominant strain, CAS1, is not associated with drug resistance is encouraging and suggests that an effective tuberculosis control program should be able to limit the high incidence of disease in this region.
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