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Molecular epidemiology of tuberculosis focusing on heterogeneity and mixed infection

Tuesday, 24 October, 2006 - 17:00
Campus: Brussels Health Campus
Faculty: Medicine and Pharmacy
auditorium R. Vanden Driessche
Isdore Chola Shamputa
phd defence

This work reviewed molecular techniques for
detection and identification of Mycobacterium
tuberculosis complex bacteria, detection of drug
resistance in clinical specimens, and described a
new PCR-based method for typing M. tuberculosis
isolates. The main focus of this work, however, was
to determine the frequency and role of
heterogeneity and initial mixed M. tuberculosis
infection in pulmonary tuberculosis (TB) patients.
We investigated this by employing two systematic
approaches. In one study, we screened individual
colonies (clones) from a single M. tuberculosis
isolate (primary isolate) of 97 TB patients using
spoligotyping, standard IS6110- based restriction
fragment length polymorphism (RFLP) typing and
PCR-based typing targeting multiple loci containing
variable number of tandem repeats (VNTRs). We
also determined drug resistance profiles (DST)
against anti-TB drugs on primary isolates and
individual colonies. Infection with different clonal
variants of the same strain and with multiple
strains (mixed infections) was detected in 8 (8.2%)
and 2 (2.1%) patients, respectively. Drug resistance
profiles of the predominant colonies for each
patient were always concordant with those of the
respective primary isolates. In another study, we
analysed isolates from multiple sputum specimens
before treatment for each of 199 inmates using
RFLP, VNTRs and DST. We detected mixed infection
in 26 (13.1%) cases, including six cases with
different resistance profiles among isolates from
different sputa. Our findings have important
implications for the correct interpretation of
molecular epidemiology data and in treatment
evaluation.