The finding that pigs with co-infections showed different AR profiles against common antimicrobial agents suggested that genetic exchange could be taking place within the same animal, generating a genetic variability in Salmonella. Horizontal transfer of AR genes or IC1 was not observed in three animals (animal codes 3, 7 and 8, Table 1) harbouring both susceptible and multi-AR strains, but genetic exchanges could not be excluded in these animals[23]. Here, AR is linked to coinfection.