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

Abstract

In 2024, 90 soil samples and 11 fecal samples were collected from nine Mongolian provinces. Using NANAT selective agar, R. equi was successfully isolated from 23 soil samples (25.6%) across five provinces and from three fecal samples (27.3%) collected in two provinces. A total of 122 isolates were identified as R. equi via choE-targeted polymerase chain reaction (PCR) and subsequently screened for virulence-associated genes (vapA, vapB, and vapN) by PCR. Of these, 17 isolates tested positive for the vapA gene, while the remaining 105 isolates were negative for both vapB and vapN. Plasmid profiling of the vapA-positive isolates revealed the presence of an 85-kb type I virulence plasmid, which is common in isolates from Europe and North America. This is the first documented detection of vapA-positive R. equi in Mongolia.