TABLE 1.
MIC changes in transconjugants.
| Antimicrobial | MICa | |||
| M. haemolytica ATCC 33396b | M. haemolytica ATCC 33396b × PM22 transconjugantc | P. multocida CCUG 17976b | P. multocida CCUG 17976b × PM22 transconjugantc | |
| Tetracyclines | ||||
| Oxytetracycline | 0.250 | 16 | 0.125 | 16 |
| Chlortetracycline | 0.125 | 2 | 0.125 | 1 |
| Macrolides | ||||
| Tylosin | 32 | 256 | 32 | 256 |
| Tilmicosin | 4 | 64 | 2 | 64 |
| Gamithromycin | 2 | 64 | 1 | 64 |
| Aminoglycosides | ||||
| Spectinomycin | 64 | 1024 | 64 | 1024 |
| Neomycin | 16 | 256 | 4 | 256 |
| β-lactams | ||||
| Penicillin G | 0.125 | 0.125 | 0.125 | 0.125 |
| Ampicillin | 0.250 | 0.250 | 0.125 | 0.125 |
| Ceftiofur | 0.125 | 0.125 | 0.125 | 0.125 |
| Sulfonamides | ||||
| Sulfamethazine | 128 | 1024 | 128 | 1024 |
| Sulfamethoxazole | 128 | 512 | 128 | 1024 |
| Others | ||||
| Enrofloxacin | 0.250 | 0.250 | 0.250 | 0.250 |
| Tiamulin | 8 | 8 | 4 | 8 |
| Clindamycin | 2 | 1024 | 4 | 1024 |
| Florfenicol | 1 | 1 | 1 | 1 |
aMinimum inhibitory concentration (MIC). The highest MIC resulting from three experiments is given. bMIC for spontaneous rifampicin-resistant mutant (Mutant MIC was equivalent to WT for all antimicrobials tested). cTransconjugants were selected for with 10 mg/L of tetracycline.