Table 2.
The minimum inhibitory concentration (MIC) range and resistance rates among Escherichia coli isolates from pups originating from two kennels (A and B).
| Substancea | MIC range (μg/mL) | MIC50 | MIC90 | Resistance breakpoints (μg/mL)b | No. of resistant isolates (%)/No. of pups that harboured resistant isolate(s) (%) | ||
|---|---|---|---|---|---|---|---|
| Total | Kennel A | Kennel B | |||||
| (n = 86/43) | (n = 50/25) | (n = 36/18) | |||||
| AMP | 2 - >512 | >512 | >512 | ≥32 | 52 (60.5)/30 (69.8) | 29 (58.0)/17 (68.0) | 23 (63.9)/13 (72.2) |
| CFZ | 8 - 128 | 4 | 8 | ≥32 | 5 (5.8)/3 (7.0) | 0 (0)/0 (0) | 5 (13.9)*/3 (16.7) |
| CEF | ≤0.125 - 32 | 0.5 | 1 | ≥8 | 5 (5.8)/3 (7.0) | 0 (0)/0 (0) | 5 (13.9)*/3 (16.7) |
| DHS | 2 - >512 | 512 | >512 | ≥32 | 57 (66.3)/32 (74.4) | 35 (70.0)/19 (76.0) | 22 (61.1)/13 (72.2) |
| GEN | 0.5 - 256 | 1 | 128 | ≥16 | 16 (18.6)/12 (27.9) | 16 (32.0)*/12 (48.0)* | 0 (0)/0 (0) |
| KAN | 2 - >512 | 4 | 16 | ≥64 | 3 (3.5)/2 (4.7) | 3 (6.0)/2 (8.0) | 0 (0)/0 (0) |
| OTC | 1 - 512 | 2 | 512 | ≥16 | 23 (26.7)/17 (39.5) | 18 (36.0)*/14 (56.0)* | 5 (13.9)/3 (16.7) |
| CHL | 4 - >512 | 8 | 512 | ≥32 | 23 (26.7)/17 (39.5) | 18 (36.0)*/14 (56.0)* | 5 (13.9)/3 (16.7) |
| NAL | 2 - >512 | 4 | 16 | ≥32 | 7 (8.1)/5 (11.6) | 2 (4.0)/2 (8.0) | 5 (13.9)/3 (16.7) |
| ENR | ≤0.03 - 256 | 0.06 | 1 | ≥4 | 5 (5.8)/3 (7.0) | 0 (0)/0 (0) | 5 (13.9)*/3 (16.7) |
| SXT | ≤0.25/4.75 - >64/1216 | 1/19 | >64/1216 | ≥16/304 | 36 (41.9)/21 (48.8) | 27 (54.0)*/16 (64.0)* | 9 (25.0)/5 (27.8) |
aAMP, ampicillin; CFZ, cefazolin; CEF, ceftiofur; DHS, dihydrostreptomycin; GEN, gentamicin; KAN, kanamycin; OTC, oxytetracycline; CHL, chloramphenicol; NAL, nalidixic acid; ENR, enrofloxacin; SXT, trimethoprim-sulfamethoxazole.
bThe breakpoints for AMP, CFZ, CEF, GEN, KAN, OTC, CHL, ENR and SXT, and that for NAL were based on CLSI document M31-A3 [9] and M100-S20 [8], respectively, whereas the breakpoint of DHS was based on an epidemiological cut-off value according to another report [10]