Table 1.
Strain | MIC (μg/ml) of macrolide |
|||
---|---|---|---|---|
Tylosin | Tilmicosin | Tildipirosin | Tulathromycin | |
M. haemolytica 11935 | 64 | 4 | 0.5 | 2 |
P. multocida 4407 | 32 | 4 | 1 | 0.5 |
E. coli ATCC 25922 | 512 | 128 | 16 | 16 |
E. coli AS19rlmAI | 1 | 2 | 0.5 | 1 |
P. multocida 4407 and M. haemolytica 11935 are susceptible strains that contain none of the macrolide resistance determinants (4, 19). E. coli ATCC 25922 also lacks any resistance determinants and is a wild-type strain with regard to cell wall/membrane structures. The hyperpermeable strain AS19rlmAI is described in Table 2. Quality controls were included as previously described (19).