Use of genotyping based clustering to quantify recent tuberculosis transmission in Guadeloupe during a seven years period: analysis of risk factors and access to health care
Résumé
Background:
The present study aimed to characterize
Mycobacterium tuberculosis
population structure and to
identify transmission chains and risk factors by prospective molecular typing in conjunction with conventional
epidemiological investigations in the French overseas department of Guadeloupe.
Methods:
The study included all the culture-positive TB cases (1 clinical isolate per patient; n = 129) diagnosed
between a seven year period (April 4
th
, 1999 to December 31
st
, 2005). Prospective molecular typing was performed
using spoligotyping and VNTRs, and a subset of 44
M. tuberculosis
isolates found to be clustered was retrospectively
typed using 12-loci MIRUs. Data were compared using the SITVIT2 database, followed by analysis of risk factors in
function of clustering of the isolates and available demographic and socioeconomic data.
Results:
The study sample was characterized by a majority of new cases (87.4%); a moderate proportion of drug-
resistance (7.8%); a high level of immigration (51.2% foreign-born) originating from high TB/HIV incidence
neighboring islands such as Haiti or Dominican Republic; lower socioeconomic conditions (70.7% of jobless,
average income 824 EUR/month); and a significantly higher proportion of TB/HIV co-infected cases (38.2% vs. 8.5%;
p < 0.001
), and extrapulmonary disease (18.2% vs. 4.8%;
p < 0.02
) among migrants as compared to French patients.
The study revealed an important delay in access to healthcare with a median delay of 74.5 days between the 1st
symptoms and clinical suspicion of TB. Prospective molecular typing based on spoligotyping and 5-loci VNTRs
showed that evolutionary recent Euro-American lineages predominated in Guadeloupe (91.5% of isolates). In
conjunction with epidemiological data, it allowed to estimate a recent transmission rate of 18.6%, which was close
to the rate of 16.7% estimated using retrospective 12-loci MIRU typing. Although a higher proportion of cases in
older age-group were apparently linked to reactivation; univariate analysis of risk factors did not allow pinpointing
specific risk factors for a patient to belong to a TB transmission group.
Conclusions:
Ongoing TB transmission in the insular, low TB-incidence setting of Guadeloupe can be defined as
follows: (i) a significant proportion of imported cases of the disease from neighboring islands; (ii) significantly higher
TB/HIV coinfection among foreign-born cases; and, (iii) a higher proportion of cases affecting older age-group
among French patients due to reactivation. This study emphasizes the need for universal typing using
spoligotyping and 15-loci MIRUs in prospective studies.
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