Confirmation that MS2/28.1 is preceded by the unique vlhA1 promoter sequence. Primer EXpro, which anneals to the vlhA1 promoter, was combined with either vlhA1R (lanes b) or with ORF5.1R (lanes c). No amplification from genomic DNA extracted from the four colonies was obtained with the vlhA1-specific reverse primer (lanes b). Expected amplicon was obtained with primers EXpro/ORF5.1R (lanes c). PCR amplification of the full length MS2/28.1 was obtained with the primers pair EXproint and 2/28.1Rev (lanes d). As negative control, PCR was performed with no genomic M. synoviae DNA (lane a). Lane M; DNA size marker (1 kb).