Table 1.
Antimicrobial susceptibility of A. butzleri strains (n = 40).
| Strain | MIC (µg/mL) (R/S) | |||||
|---|---|---|---|---|---|---|
| AMP | AZM | GEN | TET | ERY | CIP | |
| CH11 | 64 (R) | 32 (R) | 0.75 (S) | 3 (R) | 8 (S) | 0.25 (S) |
| CH26 | 64 (R) | 32 (R) | 1.5 (S) | 3 (R) | 12 (R) | 0.125 (S) |
| CH37 | 64 (R) | 32 (R) | 0.75 (S) | 3 (R) | 6 (S) | 0.25 (S) |
| CH58 | 32 (R) | 3 (S) | 1 (S) | 3 (R) | 6 (S) | 0.25 (S) |
| CH64 | 4 (S) | 2 (S) | 0.75 (S) | 2 (S) | 4 (S) | 12 (R) |
| CH75 | 16 (R) | 32 (R) | 1.5 (S) | 2 (S) | 24 (R) | 0.125 (S) |
| CH101 | 24 (R) | 2 (S) | 0.5 (S) | 2 (S) | 3 (S) | 0.19 (S) |
| H2 | 24 (R) | 1 (S) | 0.5 (S) | 0.75 (S) | 1.5 (S) | 0.047 (S) |
| H3 | 12 (R) | 1.5 (S) | 0.38 (S) | 1 (S) | 3 (S) | 0.032 (S) |
| H14 | 8 (S) | 2 (S) | 1 (S) | 2 (S) | 4 (S) | 0.125 (S) |
| H18 | 6 (S) | 2 (S) | 0.75 (S) | 1.5 (S) | 4 (S) | 0.19 (S) |
| H19 | 12 (R) | 2 (S) | 1 (S) | 1.5 (S) | 4 (S) | 0.125 (S) |
| H24 | 16 (R) | 2 (S) | 0.5 (S) | 1.5 (S) | 4 (S) | 0.064 (S) |
| H26 | 12 (R) | 12 (R) | 1 (S) | 1 (S) | 6 (S) | 0.064 (S) |
| H27 | 96 (R) | 2 (S) | 2 (S) | 3 (R) | 4 (S) | 0.125 (S) |
| H28 | 12 (R) | 24 (R) | 0.75 (S) | 3 (R) | 8 (S) | 0.19 (S) |
| H31 | 64 (R) | 32 (R) | 0.75 (S) | 3 (R) | 12 (R) | 0.125 (S) |
| RCM39 | 12 (R) | 32 (R) | 2 (S) | 2 (S) | 12 (R) | 0.25 (S) |
| RCM42 | 64 (R) | 1.5 (S) | 1 (S) | 1.5 (S) | 4 (S) | 0.064 (S) |
| RCM45 | 12 (R) | 24 (R) | 1.5 (S) | 2 (S) | 12 (R) | 0.19 (S) |
| RCM60 | 16 (R) | 4 (S) | 2 (S) | 1.5 (S) | 2 (S) | 0.125 (S) |
| RCM62 | 32 (R) | 1.5 (S) | 1.5 (S) | 1.5 (S) | 0.75 (S) | 0.064 (S) |
| RCM63 | 48 (R) | 2 (S) | 0.75 (S) | 1.5 (S) | 4 (S) | 0.064 (S) |
| RCM65 | 64 (R) | 2 (S) | 0.75 (S) | 1.5 (S) | 4 (S) | 0.064 (S) |
| RCM69 | 32 (R) | 2 (S) | 1.5 (S) | 2 (S) | 3 (S) | 0.094 (S) |
| RCM70 | 24 (R) | 2 (S) | 2 (S) | 1.5 (S) | 2 (S) | 0.125 (S) |
| RCM74 | 16 (R) | 12 (R) | 2 (S) | 1.5 (S) | 4 (S) | 0.125 (S) |
| RCM80 | 48 (R) | 2 (S) | 1 (S) | 1.5 (S) | 6 (S) | 0.19 (S) |
| S41 | 64 (R) | 24 (R) | 0.75 (S) | 3 (R) | 6 (S) | 0.19 (S) |
| S42 | 64 (R) | 32 (R) | 0.75 (S) | 3 (R) | 12 (R) | 0.19 (S) |
| W19 | 96 (R) | 32 (R) | 0.75 (S) | 1.5 (S) | 12 (R) | 0.064 (S) |
| W20 | 48 (R) | 32 (R) | 1 (S) | 3 (R) | 6 (S) | 0.19 (S) |
| W23 | 48 (R) | 24 (R) | 1 (S) | 4 (R) | 6 (S) | 0.25 (S) |
| W33 | 96 (R) | 32 (R) | 1 (S) | 2 (S) | 12 (R) | 0.125 (S) |
| W41 | 96 (R) | 48 (R) | 1 (S) | 2 (S) | 12 (R) | 0.125 (S) |
| W43 | 192 (R) | 16 (R) | 0.75 (S) | 2 (S) | 8 (S) | 0.064 (S) |
| W44 | 64 (R) | 12 (R) | 0.75 (S) | 3 (R) | 4 (S) | 0.125 (S) |
| W46 | 48 (R) | 64 (R) | 0.5 (S) | 4 (R) | 48 (R) | 0.75 (R) |
| W48 | 256 (R) | 16 (R) | 0.75 (S) | 1.5 (S) | 6 (S) | 0.064 (S) |
| W50 | 96 (R) | 24 (R) | 1 (S) | 3 (R) | 12 (R) | 0.19 (S) |
Since no breakpoint values are available for A. butzleri, strains were classified as susceptible (S) or resistant (R) by comparing minimum inhibitory concentration (MIC) data with European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints for Enterobacterales (ampicillin and gentamicin) or Campylobacter coli (azithromycin, tetracycline, erythromycin, and ciprofloxacin) [53]. Resistance breakpoint (µg/mL): ampicillin (AMP) > 8; azithromycin (AZM) > 8; gentamicin (GEN) > 2; tetracycline (TET) > 2; erythromycin (ERY) > 8; ciprofloxacin (CIP) > 0.5.