Análise espacial da transmissão de genotipos de Mycobacterium tuberculosis em Vitoria, ES-Brasil

Abstract

Background. Genotyping Mycobacterium tuberculosis isolates allows study of dynamics of tuberculosis (TB) transmission, while geoprocessing allows concomitant spatial analysis of clinical and epidemiological data. In the present study, genotyping data and spatial analysis were combined to characterize TB transmission in VitóriaES-Brazil to identify distinct neighborhoods and risk factors associated with recent TB transmission. Methods. From 2003 to 2007, 503 isolates were genotyped by IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping. The spatial analysis included Kernel density estimation (KDE), k-function analysis on predicted estimates from a random-effects logit model and a t-test distance analysis. M. tuberculosis isolates belonging to identical RFLP patterns (clusters) were considered to represent recent TB infection (cases). Results. Of 503 genotyped isolates, 242 (48%) were categorized into 70 distinct clusters belonging to 12 RFLP families. The overall proportion of recent transmission was 34.2%. Kernel density maps indicated three areas of most intense concentration of cases. K-function analysis of the largest RFLP clusters and families showed that both co-localized in space. The distance analysis confirmed these results and also showed that unique-pattern strains (controls) randomly distributed in space. A logit model with random neighborhood effects was used to evaluate univariate and multivariate associations. When the predicted probabilities for each neighborhood were mapped, they identified the neighborhoods with high risk for recent transmission. Conclusions. Spatial and genotypic clustering of M. tuberculosis isolates revealed ongoing active transmission of TB caused by a small subset of strains in a subset of neighborhoods of the city. Such information provides an opportunity to target TB transmission control, such as through rigorous and more focused contact investigation programs.