December 2025: New study finds presence of antibiotic resistant strain of Rhodococcus equi bacteria in Japan, China, East Asia and Ireland. These findings underscore the need for ongoing global surveillance and control of this bacteria in international race-horses. Rhodococcus equi can cause life-threatening pneumonia in young foals, posing a serious problem for horse welfare and the equine industry. The infection can also affect other animals and humans, where it is always severe, making zoonotic spread of antibiotic resistance a major concern. A multi-drug resistance strain of Rhodococcus equi (MDR-RE-2287) was originally identified on US horse farms in the early 2000s. This same strain was subsequently found in Ireland in 2016 and again in 2021. Multidrug resistant strain spreading globally A new international study from the Vázquez Boland lab in the Institute for Regeneration and Repair and their collaborators, has found that this multidrug-resistant Rhodococcus equi has now spread globally, likely through the international movement of horses.In the current study, the researchers analysed two samples collected from race horses in Japan in 2021 and 2023. Genetic testing confirmed that they both belonged to the same highly resistant strain previously found in the Us and Ireland. By examining international genetic databases, they also found evidence that this strain is circulating in China.The discovery of the strain in East Asia shows that multidrug-resistant Rhodococcus equi has now spread globally, likely through the international movement of horses. The study also found signs of continued importation of this strain into Ireland, and identified a new sub-variant that is distinct from the original Irish strains. Multidrug resistant Rhodococcus equi has spread from the US to Ireland, and into east Asia. Rhodococcus pneumonia is notoriously difficult to treat, and the global establishment of the bacterial variant with resistance to the only antibiotics that work against the disease in foals is a worrying development for the equine industry. Since human Rhodococcus equi infections can also be spread from animals to humans, the global spread of the deadly variant also represents a public health threat. Prof José Vázquez-Boland IRR Group Leader and paper’s corresponding author The authors of the new study say that international monitoring of this resistant strain must continue and be strengthened. Horses are frequently transported for breeding, racing, and other sporting events, creating opportunities for the bacteria to spread. Testing horses for Rhodococcus equi before international transport - even when they show no signs of illness - is essential, as the bacterium can be present without obvious symptoms.Research into new treatments and the development of a vaccine should also be prioritised, since no commercial vaccine currently exists to protect horses against this dangerous infection.This work was funded by the Horserace Betting Levy Board. Related links José Vázquez BolandInstitute of Regeneration and RepairSpread of R. equi MDR-RE 2287 from the US to Ireland, Val-Calvo et al. 2022, Emerg Infect Dis Update on emerging multidrug-resistant Rhodococcus equi, Vázquez-Boland et al. 2024, Vet Rec Publication date 19 Dec, 2025
