Detection of subspecies and subtypes of M. avium using PCR for large sequences polymorphic among strains of M. avium. On the top panel, 11 samples were tested for LSPA 8 using a three-primer PCR. Lanes: L, 100-bp ladder; 1 to 4, M. avium subsp. paratuberculosis strains; 5 and 6, nonparatuberculosis strains of M. avium; 9, mixed sample (M. avium 104 and M. avium subsp. paratuberculosis K10); 10, M. intracellulare ATCC 13950 strain; 11, water. In the bottom panel, four samples were tested for LSPA 20 and four samples are tested for LSPA 17 using three-primer PCRs. Lanes: L, 100-bp ladder; 1 and 2, M. avium subsp. paratuberculosis C type; 3 and 4, M. avium subsp. paratuberculosis S type; 5, water; 6 and 7, M. avium subsp. hominissuis; 8 and 9, M. avium subsp. avium bird type; 10, water.