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

The research paper presents a study on the isolation and identification of vapA-positive Rhodococcus equi from soil and fecal samples in Mongolia. It is the first documented occurrence of this type of bacteria in the country.

Sample Collection and Examination

• In 2024, soil and fecal samples were taken from various locations in nine provinces of Mongolia. In total, 90 soil samples and 11 fecal samples were collected.
• The researchers used NANAT selective agar to isolate the Rhodococcus equi bacteria from the samples. This method proved successful, with the bacteria successfully isolated from 23 soil samples (25.6%) across five provinces and three fecal samples (27.3%) collected in two provinces.

Identification of R. equi and Screening of Virulence-Associated Genes

• From the samples, a total of 122 isolates were identified as Rhodococcus equi through the use of choE-targeted polymerase chain reaction (PCR).
• The researchers then proceeded to screen these isolates for virulence-associated genes – vapA, vapB, and vapN – by PCR. These genes play a role in the bacteria’s ability to cause disease.
• The results showed that 17 of the isolates tested positive for vapA. The rest, 105 in number, tested negative for both vapB and vapN.

Plasmid Profiling and Detection of vapA-positive R. equi

• The researchers then focused on the 17 vapA-positive isolates and conducted plasmid profiling. Plasmids are small, circular, double-stranded DNA molecules that are distinct from a cell’s chromosomal DNA and can replicate independently.
• The plasmid profile revealed the presence of an 85-kb type I virulence plasmid. This type of plasmid is common in Rhodococcus equi isolates from Europe and North America.
• The study therefore marked the first detection of vapA-positive Rhodococcus equi in Mongolia, shedding light on the presence and prevalence of this bacterium in Mongolian soil and fecal matter.