Serovar-specific detection of amplicons from A. pleuropneumoniae serovars 13–14 and 16–18 by APP mPCR2. An apxIV (418-bp) amplicon is detected in all 18 serovar reference strains, and an additional 1339 bp nadV amplicon is detected only in the biovar 2 strains. Lane M contains molecular size markers (100-bp Plus DNA Ladder; Invitogen). Lanes 1 to 18 contain the following strains: 1, 4074 T; 2, S1536; 3, S1421; 4, M62; 5, L20; 6, Femø; 7, WF83; 8, 405; 9, CVJ13261; 10, D13039; 11, 56153; 12, 8329; 13, N-273; 14, 3906; 15, HS143; 16, A-85/14; 17, 16287-1; 18, 7311555. Lane 19 contains the biovar 2 serovar 17 isolate, 14-022, and Lane 20 contains A. suis CCM 5586T.