Comparative genomics of drug-resistant strains of Mycobacterium tuberculosis in Ecuador

Molecular epidemiology of Mycobacterium tuberculosis in Ecuador: Recent advances and future challenges

Tuberculosis (TB) is one of the three leading causes of death from a single infectious agent, Mycobacterium tuberculosis (MTB), together with COVID-19 and HIV/AIDS. This disease places a heavy burden on countries with low socio-economic development and aggravates existing inequalities. For the year 2021, estimations for Ecuador were 8500 TB cases, of which 370 were associated to multiple drug resistance (TB-MDR), and 1160 deaths. In the same year, Ecuador notified 5973 total cases, 401 of them were TB-MDR, pointing out an under diagnosis problem. The few molecular epidemiology studies available conclude that L4 is the most prevalent MTB lineage in Ecuador (with LAM as the main L4 sublineage), but L2-Beijing family is also present at low prevalence. Nevertheless, with less than 1 % MTB isolates genetically characterized by either MIRU-VNTR, spolygotyping or WGS to date, molecular epidemiology research must me improved to assist the TB surveillance and control program in Ecuador.

A first insight into tuberculosis transmission at the border of Ecuador and Colombia: a retrospective study of the population structure of Mycobacterium tuberculosis in Esmeraldas province

Objective

Tuberculosis (TB) is a major public health concern in Ecuador and Colombia, considering that both countries are high-burden TB settings. Molecular epidemiology is crucial to understand the transmission dynamics of Mycobacterium tuberculosis complex (MTBC) and to identify active transmission clusters of regional importance.

Methods

We studied the potential transmission of TB between Colombia and Ecuador through the analysis of the population structure of MTBC lineages circulating in the Ecuadorian province of Esmeraldas at the border with Colombia. A total of 105 MTBC strains were characterized by 24-loci MIRU-VNTR and spoligotyping.

Results

MTBC lineage 4 is only present in Esmeraldas; no MTBC strains belonging to Lineage 2-sublineage Beijing were found despite its presence in other provinces of Ecuador and, in Colombia. Genotyping results revealed a high degree of diversity for MTBC in Esmeraldas: Neither active transmission clusters within this province nor including MTBC strains from Colombia or other provinces of Ecuador were found.

Conclusion

Our data suggest that tuberculosis dynamics in this rural and isolated area may be not related to highly transmitted strains but could be influenced by other health determinants that favor TB relapse such as poverty and poor health system access. Further studies including a larger number of MTBC strains from Esmeraldas are necessary to test this hypothesis.