Isolation of vapA-positive Rhodococcus equi from soil and fecal samples in Mongolia

Area of Science:

• Veterinary Microbiology
• Infectious Diseases
• Environmental Health

Background:

• Rhodococcus equi is an important pathogen causing significant economic losses in livestock, particularly foals.
• The presence and distribution of R. equi, especially virulent strains, in Mongolia remain largely uncharacterized.
• Virulence factors, such as the vapA gene, are critical for R. equi pathogenicity.

Purpose of the Study:

• To investigate the prevalence and genetic characteristics of Rhodococcus equi in Mongolian soil and fecal samples.
• To identify the presence of virulence-associated genes (vapA, vapB, vapN) in R. equi isolates from Mongolia.
• To report the first detection of vapA-positive R. equi in Mongolia.

Main Methods:

• Collection of 90 soil and 11 fecal samples from nine Mongolian provinces in 2024.
• Isolation of R. equi using NANAT selective agar.
• Identification of R. equi isolates using choE-targeted polymerase chain reaction (PCR).
• Screening for virulence-associated genes (vapA, vapB, vapN) via PCR.
• Plasmid profiling of vapA-positive isolates.

Main Results:

• Rhodococcus equi was isolated from 25.6% of soil samples and 27.3% of fecal samples.
• A total of 122 R. equi isolates were identified.
• Seventeen isolates (13.9%) tested positive for the vapA gene; 105 isolates were negative for vapB and vapN.
• VapA-positive isolates harbored an 85-kb type I virulence plasmid, common in European and North American strains.
• This study marks the first documented detection of vapA-positive R. equi in Mongolia.

Conclusions:

• The presence of R. equi, including virulent strains carrying the vapA gene, is confirmed in Mongolia.
• The identified virulence plasmid suggests potential international dissemination or shared origins of R. equi strains.
• These findings highlight the importance of continued surveillance for R. equi in Mongolia to inform disease prevention and control strategies.