TABLE 5.
Concordance between disk diffusion and broth microdilution of 48 Mannheimia haemolytica isolates
| Disk diffusion/broth microdilution susceptibility (S, I, or R) | No. isolates (%) | Error type a | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Antimicrobial | Timepoint | S/S | S/I | S/R | I/S | I/I | I/R | R/S | R/I | R/R | P‐value | Concordant | Discordant | Very major | Major | Minor |
| FLOR | Arrival | 26 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 26 (100%) | 0 | 0 | 0 | 0 |
| Revacc | 7 | 5 | 1 | 0 | 1 | 0 | 0 | 0 | 8 | .06 | 16 (72.7%) | 6 (27.3%) | 1 (3.8%) | 0 | 5 (22.7%) | |
| CEF | Arrival | 26 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 26 (100%) | 0 | 0 | 0 | 0 |
| Revacc | 21 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 21 (95.5%) | 1 (4.5%) | 0 | 0 | 1 (4.5%) | |
| ENR | Arrival | 26 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 26 (100%) | 0 | 0 | 0 | 0 |
| Revacc | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 22 | 1 | 22 (100%) | 0 | 0 | 0 | 0 | |
| TIL | Arrival | 17 | 2 | 1 | 5 | 1 | 0 | 0 | 0 | 0 | .5 | 18 (69.2%) | 8 (30.8%) | 1 (3.8%) | 0 | 7 (26.9%) |
| Revacc | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 22 | 1 | 22 (100%) | 0 | 0 | 0 | 0 | |
| TUL | Arrival | 20 | 0 | 0 | 6 | 0 | 0 | 0 | 0 | 0 | .06 | 20 (76.9%) | 6 (23.1%) | 0 | 0 | 6 (23.1%) |
| Revacc | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 21 | 1 | 21 (95.5%) | 1 (4.5%) | 0 | 0 | 1 (4.5%) | |
Notes: Concordance for arrival isolates assessed out of 26 isolates, concordance for revaccination isolates assessed out of 22 isolates. Susceptibility interpretation indicated as susceptible (S), intermediate (I), and resistant (R).
Abbreviations: CEF, ceftiofur; ENR, enrofloxacin; FLOR, florfenicol; TIL, tilmicosin; TUL, tulathromycin.
a
Very major = classified as susceptible by disk diffusion but as resistant by broth microdilution; Major = classified as resistant by disk diffusion but as susceptible by broth microdilution; Minor = classified as intermediate by only one method.