A First Insight on the Population Structure of Mycobacterium tuberculosis Complex as Studied by Spoligotyping and MIRU-VNTRs in Santiago, Chile

Abstract

Tuberculosis (TB) remains a significant public health problem worldwide, but the ecology of the prevalent mycobacterial strains, and their transmission, can vary depending on country and region. Chile is a country with low incidence of TB, that has a geographically isolated location in relation to the rest of South American countries due to the Andes Mountains, but recent migration from neighboring countries has changed this situation. We aimed to assess the genotypic diversity of Mycobacterium tuberculosis complex (MTBC) strains in Santiago, Chile, and compare with reports from other Latin-American countries. We analyzed MTBC isolates from pulmonary tuberculosis cases collected between years 2008 and 2013 in Central Santiago, using two genotyping methods: spoligotyping and 12-loci mycobacterial interspersed repetitive unit-variable number of tandem repeats (MIRU-VNTRs). Data obtained were analyzed and compared to the SITVIT2 database. Mean age of the patients was 47.5 years and 61% were male; 11.6% were migrants. Of 103 strains (1 isolate/patient) included, there were 56 distinct spoligotype patterns. Of these, 16 strains (15.5%) corresponded to orphan strains in the SITVIT2 database, not previously reported. Latin American and Mediterranean (LAM) (34%) and T (33%) lineages were the most prevalent strains, followed by Haarlem lineage (16.5%). Beijing family was scarcely represented with only two cases (1.9%), one of them isolated from a Peruvian migrant. The most frequent clustered spoligotypes were SIT33/LAM3 (10.7%), SIT53/T1 (8.7%), SIT50/H3 (7.8%), and SIT37/T3 (6.8%). We conclude that LAM and T genotypes are the most prevalent genotypes of MTBC in Santiago, Chile, and together correspond to almost two thirds of analyzed strains, which is similar to strain distribution reported from other countries of Latin America. Nevertheless, the high proportion of SIT37/T3, which was rarely found in other Latin American countries, may underline a specific history or demographics of Chile related to probable human migrations and evolutions.

Genetic Structuration, Demography and Evolutionary History of Mycobacterium tuberculosis LAM9 Sublineage in the Americas as Two Distinct Subpopulations Revealed by Bayesian Analyses

“…Majority of data regarding distribution of M . tuberculosis lineages and sublineages in the Americas has been published in earlier individual studies focusing on respective population structures within a country [ 8 , 9 , 13 – 15 , 30 – 55 ]. However, to have a global overview of mapping at the level of the continent, we hereby analyze metadata allowing greater resolution in order to more deeply explore the genetic structuration of predominant lineages on a total of 21183 M .…”

“…For having an overview of global distribution of all M . tuberculosis lineages in the Americas, readers may refer to S1 Fig , which is an updated version of a distribution map published recently [ 30 ], as well as distribution maps of two other predominant lineages T and H ( S2 and S3 Figs).…”

“…tuberculosis clinical isolates fully available without restriction. All data used in our study are either available at: http://www.pasteur-guadeloupe.fr:8081/SITVIT_ONLINE , or in published studies [ 8 , 9 , 13 – 15 , 30 – 55 ]. This database currently centralizes data on 120000 M .…”

Polimorfismos genéticos asociados a la inmunidad innata y la susceptibilidad genética a la tuberculosis

“…Asimismo, que la incidencia de la tB era consistentemente más alta en la población Mapuche, la que mostró 2,7 veces más riesgo a la tB que la población no Mapuche de la región del Bío-Bío 10 . el 2016, las mayores tasas de morbilidad total de tBtF ocurrieron en el norte de chile (I: tarapacá [40, tanto, factores genéticos del ser humano 11 como de los genotipos de Mtb 12 , contribuyen a la variabilidad interindividuo y de fenotipos de Mtb relacionados con la patogénesis y la presentación de la enfermedad 12,13 . La ecología de cepas prevalentes y su transmisión pueden variar dependiendo del continente, país o región.…”

“…el 15,5% correspondió a cepas huérfanas en la base de datos SItVIt2. La familia Beijing resultó con una baja representación (1,9%) 12 . La familia SIt37/t3 mostró una alta proporción, a pesar que rara vez se encuentra en los países latinoamericanos; quizá ello revela una historia de chile relacionada con migraciones humanas y evolución 12,13 .…”