European Society of Mycobacteriology - Instituto Nacional de Saúde ...

PP-12
Genomic characterization of Lisboa
family strains by deletion analysis
João Perdigão, Carla Silva and Isabel Portugal
Centro de Patogénese Molecular, URIA, Faculdade de Farmácia da Universidade de Lisboa
Multidrug and extensive drug resistant tuberculosis poses a very serious threat for public health. Lisbon Health Region
has one of the world’s most serious situations regarding this problem. Such, is the result of a continued circulation of an
endemic and predominant strains of a particular genetic family – Lisboa family. Little is known regarding the phylogeny,
relative virulence and genetic background of these strains. The loss or deletion of specific genomic regions constitutes
the most important way by which Mycobacterium tuberculosis diverges and adapts. Several deletions, named Regions
of Difference (RD), have already been described and associated with phylogeographic lineages. The characterization of
Lisboa family in this manner may elucidate its origin and perhaps be helpful in explaining its high prevalence.
Three representative clinical isolates of different genetic clusters of strains circulating in Lisbon Health Region were
screened for the presence of 16 distinct RDs. Deletion detection was performed by PCR carried out using primers flanking
each RD. Confirmation was performed by sequencing analysis.
All three isolates were found to possess four of the tested deletions: TbD1, pks15/1, RD174 and RD RIO . It was not possible
to discriminate between the strains using this deletion typing approach. However, it was possible to infer on the
phylogeography of these strains. The presence of TbD1 and pks15/1 deletion positions the strains in the modern and
Euro-American lineage, respectively. On the other hand, RD174 suggests that the analyzed strains are related to the
West-African sub-lineage.
The present study point toward the fact that Lisboa strains and others circulating in Lisbon belong to Mycobacterium
tuberculosis modern lineages of the Euro-American lineage, West-African sub-lineage, therefore revealing more on Lisboa family’s origin.
84 ESM 2009