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Table 2 The minimum inhibitory concentration (MIC) range and resistance rates among Escherichia coli isolates from pups originating from two kennels (A and B).

From: Clonal spread of antimicrobial-resistant Escherichia coli isolates among pups in two kennels

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)
  1. aAMP, ampicillin; CFZ, cefazolin; CEF, ceftiofur; DHS, dihydrostreptomycin; GEN, gentamicin; KAN, kanamycin; OTC, oxytetracycline; CHL, chloramphenicol; NAL, nalidixic acid; ENR, enrofloxacin; SXT, trimethoprim-sulfamethoxazole.
  2. 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]