Molecular epidemiology of Rhodococcus equi in slaughtered swine, cattle and horses in Poland

BACKGROUND: Rhodococcus equi is an emerging zoonotic presumably foodborne pathogen. Since the data on the worldwide prevalence of R. equi in meat animals are scarce, the present study aimed to investigate the molecular epidemiology of R. equi in swine, cattle and horse carcasses intended for human consumption in Poland. RESULTS: Totally 1028 lymph node samples were examined. R. equi was isolated from 26.6 % (105/395) swine and 1.3 % (3/234) bovine healthy submaxillary lymph nodes. In horses, R. equi was isolated only from 0.5 % (1/198) samples of middle tracheo-branchiales lymph node while no lymphocentrum retropharyngeum sample was positive (0/198). The purulent lesions were observed only in 0.8 % swine submaxillary lymph nodes samples (3/398) and in two of them R. equi was detected. All bovine and most of swine isolates (98.1 %) were vapB-positive. 87.9 % of swine isolates carried 95-kb type 5 plasmid, 3.7 % type 1 and plasmid types: 4, 7, 10, 11, 21, 31 were carried by a single isolate (0.9 %). All bovine isolates carried VAPB type 26. Single horse isolate was vapA-positive and carried plasmid VAPA 85-kb type I. CONCLUSIONS: The prevalence of vapB-positive R. equi in investigated healthy swine intended for human consumption was very high. Not only swine, but also even apparently healthy cattle or horse carcasses should be considered as a potential source of R. equi for humans, especially in countries where undercooked or raw beef or horsemeat is traditionally consumed.