MOLECULAR EPIDEMIOLOGY OF MYCOBACTERIUM TUBERCULOSIS COMPLEX IN PALERMO, ITALY

Abstract

Background: We aimed to investigate the molecular epidemiology of Mycobacterium tuberculosis complex (MTBC) in the province of Palermo, Italy, by characterizing 183 isolates identified in the years 2004-2012. A comparison with 104 MTBC strains identified in the same geographic area in the years 1994-2000 was also carried out. Methods: MTBC isolates were analyzed by spoligotyping and the 24 mycobacterial interspersed repetitive unit (MIRU)-variablenumber tandem-repeat (VNTR) method typing. Susceptibility testing to streptomycin, isoniazid, rifampin and ethambutol was also carried out. Furthermore, the spoligotyping dataset obtained from 104 MTBC isolates identified in the years 1994-2000 in the same geographic area was reanalyzed. Distribution into lineages and clustering of isolates in the two periods was compared. Results: Out of the 177 isolates of MTBC submitted to molecular typing, 108 were from Italian-born and 69 from foreign-born individuals. Eleven different lineages were identified with the most represented being Haarlem, T, LAM and S. Except for the Haarlem lineage, where isolates from foreign-born patients were overrepresented, the distribution of isolates in the families belonging to the Euro-American phylogeographical clone reflected the proportions of the two subpopulations. A total of 27 strains (15.2%) were clustered and three cluster were mixed. 25% of the isolates proved to be resistant to at least one anti-TB drug, with only three isolates being categorized as multidrug resistant (MDR). When MTBC isolates identified in the years 1994-2000 were reanalyzed, lineages T, LAM, Haarlem and S proved also to be predominant. No MTBC isolates belonging to CAM, U, CAS, Turkish and Ural lineages were identified in this set of isolates. Moreover, the proportion of clustered isolates was similar, but all the clustered isolates were from Italian patients. Conclusions: A wide heterogeneity (11 lineages and 35 families-subfamilies) was detected among the MTBC strains isolated in the years 2004-2012. Ten clusters were identified, of which three mixed and four involving newly identified lineages. Compared with isolates from 1994-2000, six new lineages were detected. Comparison between distribution of lineages and the characteristics of isolates in the two consecutive periods depicts rapid and deep changes in the tuberculosis epidemiology in Palermo, Italy.