Table 2.
Characteristics of macrolide-resistance genes in Campylobacter coli strains showing varied resistance to azithromycin and erythromycina.
| Strain | Source | MIC (μg/mL) | cmeB c | ermB c | Mutations | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Azithromycin | Erythromycin | 23S rRNA | L4 | L22 | ||||||||
| -EPI | +EPI | Foldb | -EPI | +EPI | Foldb | |||||||
| A16-CF-319-1 | CM | 4 | 1 | 4 | 1 | 0.5 | 2 | - | - | wt | wt | wt |
| A16-CF-330-1 | CM | 4 | 1 | 4 | 1 | 0.5 | 2 | - | - | wt | V196A | I65V, A74G |
| A16-CF-130-1-S1 | BC | 8 | 8 | 1 | 2 | 0.5 | 4 | + | - | wt | wt | I65V, A74G |
| A16-CF-128-1-S1 | BC | 8 | 8 | 1 | 128 | 64 | 2 | - | - | wt | V121A, V196A | I65V, A74G |
| CM13-HL-BS-020 | CM | 16 | 0.5 | 32 | 32 | 0.5 | 64 | - | - | wt | V196A | I65V, A74G |
| CM13-HL-BL-031 | CM | 16 | 1 | 16 | 64 | 0.25 | 256 | - | - | wt | V196A | I65V, A74G |
| CM13-MC-BS-006 | CM | 16 | 0.125 | 128 | 64 | 2 | 32 | - | - | wt | V196A | I65V, A74G |
| DM13-MWC-SS-013 | DM | 32 | 2 | 16 | 4 | 0.125 | 32 | - | - | wt | V196A | I65V, A74G |
| DM13-MP-WS-007 | DM | 32 | 0.5 | 64 | 8 | 0.5 | 16 | - | - | wt | V196A | I65V, A74G |
| A16-CF-130-2-S1 | BC | 64 | 64 | 1 | 32 | 32 | 1 | - | - | wt | V196A | I65V, A74G |
| A16-CF-107-2-S2 | BC | 64 | 64 | 1 | 64 | 32 | 2 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-128-1-S4 | BC | 128 | 2 | 64 | 128 | 4 | 32 | - | - | wt | V196A | I65V, A74G, S109A |
| A16-CF-124-2-S3 | BC | 128 | 4 | 32 | 128 | 2 | 64 | - | - | wt | V196A | I65V, A74G, S109A |
| A16-CF-107-2-S4 | BC | ≥512 | 64 | 8 | ≥512 | 64 | 8 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-124-1-S1 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-124-1-S4 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-126-2-S1 | BC | ≥512 | 64 | 8 | ≥512 | 32 | 16 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-124-1-S5 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | - | - | A2075G | wt | I65V, A74G, S109A |
| A16-CF-126-2-S2 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | - | - | A2075G | V196A | I65V, A74G, S109A |
| A16-CF-126-2-S4 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | - | - | A2075G | V121A, V196A | I65V, A74G, S109A |
| A16-CF-118-2-S3 | BC | ≥512 | ≥512 | 1 | ≥512 | 64 | 8 | + | - | A2075G | V121A, V196A | I65V, A74G, S109A |
| A16-CF-126-1-S3 | BC | ≥512 | ≥512 | 1 | ≥512 | 32 | 16 | + | - | A2075G | V121A, V196A | I65V, A74G, S109A |
| A16-CF-126-2-S3 | BC | ≥512 | ≥512 | 1 | ≥512 | 32 | 16 | + | - | A2075G | V121A, V196A | I65V, A74G, S109A |
a. Abbreviations: CM: chicken meat; BC: breeder chicken; DM: duck meat; EPI: efflux pump inhibitor; A, Ala; G: Gly; I: Ile; S: Ser; V: Val; wt: wild type.
b. Fold values were calculated as (MIC without EPI)/(MIC with EPI).
c. +/-, indicates whether or not the target genes were detected.
The MIC breakpoints for azithromycin: susceptible, ≤ 2 μg/mL; intermediate, 4 μg/mL; and resistant, ≥ 8 μg/mL; for erythromycin: susceptible, ≤ 8 μg/mL; intermediate, 16 μg/mL; and resistant, ≥ 32 μg/mL.