FIG. 1.

Agarose gel electrophoresis of PCR products obtained by IS900 one-tube nested PCR performed on representative cheese samples. Lane 1, 100-bp molecular weight ladder (New England BioLabs Ltd., United Kingdom); lane 2, positive control sample; lanes 3 and 4, positive samples showing the 257-bp amplification product specific for M. avium subsp. paratuberculosis; lanes 5 and 6, negative samples; lane 7, negative control containing only the PCR mixture and water; lane 8, negative control with DNA isolated from a confirmed PCR- and culture-negative cheese sample.