Brachyspira hyodysenteriae is an aetiological agent of swine dysentery (SD), a transmissible infectious disease affecting pigs during the growing and finishing periods.1 Antimicrobial therapy is still considered the main method of controlling SD in pig herds and it is usually based on the administration of tylosin, lincomycin and pleuromutilins.2 The presence of B hyodysenteriae isolates resistant to these antibiotics has been reported in several countries in the last 15 years, including Italy.3–6 In Italy, the presence of multiresistant clones has been recently documented using multilocus sequence typing MLST analysis, revealing the spread of a dominant sequence type (ST), ST83 in outbreaks of SD.5 -7 B hyodysenteriae ST83 exhibits resistance to classes of drugs used for the treatment of SD, namely to macrolides, lincosamides and pleuromutilins.8 No vaccines are commercially available to prevent SD, and the eradication of the infection is still based on the use of antimicrobials, namely pleuromutilins.8 This strategy, however, is hardly applicable in case of an infection carried by a multiresistant strain. Therefore, improved biosecurity, preventing the introduction and spread of B hyodysenteriae within the herd, is still one of the major control measures for SD. Data on patterns of transmission of B hyodysenteriae are thus urgently needed to identify control measures alternative to antibiotics. However, in spite of the importance of SD in pig herds, very few papers describing the on-farm epidemiology of SD have so far been published.9 Moreover, no data are available on shedding of multiresistant B hyodysenteriae from fattening pigs in field conditions. The aim of this study is to investigate the shedding of a multiresistant B hyodysenteriae from fattening pigs raised in an endemically infected …