# Genotypic drug resistance and transmission clusters of Mycobacterium tuberculosis isolates among Ethiopian returnees from Saudi Arabia

## TL;DR

This study examines tuberculosis drug resistance and transmission among Ethiopian returnees from Saudi Arabia, finding high transmission rates and drug-resistant strains likely linked to detention centers.

## Contribution

The study identifies M. tuberculosis transmission clusters and drug resistance patterns among Ethiopian returnees, highlighting risks in congregate settings and the need for improved screening.

## Key findings

- Lineage 4 of M. tuberculosis was most prevalent, with sub-lineage 4.2.2.2 being dominant.
- 40 gene mutations conferring drug resistance were identified, and 16 transmission clusters were detected.
- 2.3% of newly diagnosed cases were MDR-TB, suggesting transmission likely occurred in Saudi Arabian detention centers.

## Abstract

Human migration significantly contributes to the global spread of infectious diseases. In recent years, Ethiopia has experienced an increased influx of returnees from the Kingdom of Saudi Arabia. These migrants were often held in densely populated and inadequately ventilated detention centers and faced a heightened risk of tuberculosis transmission. This study investigates the genotypic drug resistance and transmission clusters of M. tuberculosis among returnees from various detention centers in the Kingdom of Saudi Arabia. Whole genome sequencing (WGS) is employed to characterize the genotypic drug resistance patterns and transmission clusters of M. tuberculosis isolates in presumptive TB cases.

Following symptom screening for presumptive TB, sputum samples were collected from 161 Xpert MTB/RIF-confirmed returnees between August and December 2022. The samples were further cultured on Lowenstein-Jensen media, with 66.5% (107/161) yielding positive results. The M. tuberculosis strains were classified, and genotypic drug susceptibility was predicted. Transmission clusters were identified using a distance threshold of 12 single nucleotide polymorphisms (SNPs).

Among the 88 isolates, Lineage 4 was the most prevalent, representing 65.9% of M. tuberculosis cases among returnees. Sub-lineage 4.2.2.2 was the most dominant within this group, comprising 33% (29/88) of the isolates. Among the isolates, 40 gene mutations conferring resistance to first- and second-line anti-TB drugs were identified. Sixteen transmission clusters were identified, suggesting possible transmission events and a likely origin within the detention centers of the Kingdom of Saudi Arabia (KSA). The proportion of MDR-TB among newly diagnosed cases was 2.3% (2/88).

The clustering patterns of M. tuberculosis strain among KSA returnees possibly suggest increased transmission rates in congregate settings. Most importantly, the identified prevalence of MDR-TB, particularly among newly diagnosed TB cases, underscores the need to strengthen robust screening practices for returning migrants before they reintegrate into the community to curb TB/DR-TB transmission.