EN
The aim of the study was to assess the effectiveness of detecting virulent Rhodococcus equi strains in tracheobronchial aspirate (TBA) of foals in enzootic farms depending on foals’ age and season. Between January and July, 385 TBA samples were collected. The samples were used for culture examination on the NANAT selective medium and for DNA extraction amplified in PCR and multiplex PCR. The most positive results confirming isolated strains as R. equi species were obtained in May and June. The least positive results were obtained in April and July. Between January and March, none of the TBA samples were positive in culture and PCR. The analysis of positive results of TBA specimens in regard to foals’ age revealed that the pathogen was detected most often in foals aged 2 and 3 months and was sporadically detected in foals aged 1 and 6 months. In 14 out of 28 TBA samples, multiplex PCR examination revealed the presence of the plasmid vapA gene. The highest number of virulent strains was detected in May and June. In 14 out of 28 foals positive for R. equi in culture examination and PCR, the multiplex PCR detecting vapA gene, was negative, which categorised these strains as avirulent. The results of the studies confirm the effectiveness of detecting R. equi in TBA of foals in enzootic farms. The interpretation of the results requires taking into account foal age, season, and epizootic situation of the farm.