PCR detection of the prophage DLP12-associated genomic island. (A) PCR panel for detection of all 15 genes included in the prophage region and the two flanking genes. Porcine L. intracellularis isolate PHE/MN1-00 at passage 10 showing the presence of all prophage-associated genes (above). Loss of the prophage element at passage 60 showing the presence of flanking genes (below). (B) Absence of the entire prophage-associated island confirmed in the porcine isolate PHE/MN1-00 at passage 60 and infected horse and rabbit isolates by obtaining PCR products from the amplification of a primer pair targeting the regions immediately before and after the prophage region (forward: 5′-TCGTGAGAAACTTGTATCAATCCA-3′ and reverse: 5′-TGACAATGTTAGAGCAATGACTTTTTA3-3′).