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

PP-20
MOLECULAR EPIDEMIOLOGY OF TUBERCULosis
IN VILA NOVA DE GAIA, PORTUGAL
Tavares Magalhães, Ana 1 , Alves, Adriana 1 , Braga, Rosário 2 , Valente, Isabel 2 , Duarte, Raquel 3 and Miranda, Anabela 1
1 - Tuberculosis Reference Laboratory, Department of Infectious Diseases, National Institute of Health, Porto, Portugal
2 - Central Hospital, Vila Nova de Gaia, Portugal
3 - Chest Clinic, Vila Nova de Gaia, Portugal
DNA fingerprinting of Mycobacterium tuberculosis has provided a better understanding of the epidemiology of tuberculosis.
Restriction fragment length polymorphism based on IS6110 (RFLP-IS6110) has been the gold standard for typing
M. tuberculosis since 1993. In recent years, mycobacterial interspersed repetitive units variable number tandem repeat
(MIRU-VNTR) has been proposed as a first-line typing method for M. tuberculosis. This technique generates easily analyzed
and portable data, has a good discrimination power and has been proven useful for studying the epidemiology of
tuberculosis and the phylogeography of tuberculosis bacilli.
In the present study we evaluated the genetic diversity of M. tuberculosis clinical strains, isolated from 115 patients from
Vila Nova de Gaia, Portugal, during the period of 2004 to 2005, using the standardized MIRU-VNTR typing method based
on 15 loci, proposed by Supply and collaborators in 2006. Strain lineage designation, allelic diversity and clustering rate
were determined using the MIRU-VNTRplus identification database. The discriminative power of the method was analysed
using the Hunter and Gaston diversity index.
Based on MIRU-VNTR typing, the 115 strains were divided into 62 types as follows: 69 strains were distributed into 16
clusters containing two to eight isolates, and 46 strains had unique profiles. MIRU-VNTR revealed a clustering rate of
46% in the sample under study. The Hunter-Gaston index was 0.976. The most discriminatory loci were Mtub04, MIRU
40, MIRU10, QUB11b, Mtub30, Mtub39 and QUB26 showing an allelic diversity higher than 0,6.
The phylogenetic analysis revealed the presence of two major lineages, LAM and Haarlem, representing 60% and 27% of
the total isolates, respectively. This fact is in agreement with the M. tuberculosis phylogeography for the South of Europe.
Fourteen strains showed drug resistance but no association was established between drug resistance profile and phylogenetic
family.
MIRU-VNTR showed a good discriminatory power for typing of M. tuberculosis strains in this setting and the MIRU-
VNTRplus database is an important tool for lineage identification. This typing approach offers, simultaneously, epidemiologic
and phylogenetic information, as demonstrated. Overall, this study reveals that recent transmission of tuberculosis
is high in Vila Nova de Gaia, and that import of strains in this region is not a problem.
92 ESM 2009