First molecular characterization of Burkholderia mallei strains isolated from horses in Mongolia.

Overview

• This research article presents the first molecular analysis of Burkholderia mallei strains isolated from horses in Mongolia, using whole-genome sequencing to understand the genetic characteristics and relationships of these bacterial strains.

Background

• Glanders Disease: A severe and contagious disease primarily affecting horses, donkeys, and mules caused by the bacterium Burkholderia mallei.
• Geographical Context: Although glanders cases have been reported in Mongolia recently, detailed genetic studies on the responsible bacterial strains in this region were missing prior to this study.
• Importance of Molecular Characterization: Genetic analysis helps in tracking, understanding transmission, and controlling the disease more effectively.

Objectives of the Study

• To perform whole-genome sequencing of B. mallei strains isolated from Mongolian horses.
• To establish genetic profiling using two SNP typing methods:
• A previously developed global genotyping system based on 15 SNP markers for coverage of the B. mallei population worldwide.
• A new core genome SNP typing developed in this study to provide higher resolution.
• To identify unique genetic markers specific to Mongolian strains to improve epidemiological monitoring.

Methods

• Samples were taken from four native Mongolian horses across two different provinces in Mongolia collected in 2019 and 2022.
• Whole-genome sequencing was performed to analyze the full genetic makeup of each bacterial strain.
• Two Single Nucleotide Polymorphism (SNP) typing approaches were used:
• The 15-marker global SNP system to categorize strains within known global clusters.
• The newly developed core genome SNP typing for detailed and high-resolution strain differentiation.
• High-resolution melting analysis (HRMA) was employed to identify and track SNP markers unique to Mongolian strains.

Key Findings

• The Mongolian isolates belong to the L3B1 cluster, which includes the V-120 strain previously found in Russia, indicating a regional genetic relationship.
• Within the L3B1 cluster, the Mongolian strains form a unique subbranch that is genetically distinct from the strains isolated in neighboring countries.
• Specific SNP markers were identified that are unique to the Mongolian strains, enabling more effective molecular tracking using HRMA.
• This demonstrates a distinct phylogenetic lineage of Burkholderia mallei circulating in eastern Mongolia.

Significance and Implications

• This is the first detailed genomic characterization of B. mallei strains from Mongolia, filling a critical gap in the understanding of glanders epidemiology in the region.
• The unique genetic markers discovered will aid in molecular epidemiological surveillance and monitoring of glanders within Mongolia and neighboring countries.
• The findings may enhance regional disease control efforts by providing tools to trace and track outbreaks more precisely.
• Improved molecular diagnostics such as HRMA specific to the Mongolian subbranch could facilitate rapid identification and containment of glanders cases.