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Table 4 Total number (n) and percentage of phenotype observed within isolates recovered from MacConkey agar amended with 50 μg/ml ampicillin after diet administration of control and three antimicrobial treatments.

From: Distribution and characterization of ampicillin- and tetracycline-resistant Escherichia colifrom feedlot cattle fed subtherapeutic antimicrobials

  Treatment
Phenotype CON % (n) T % (n) TS % (n) V % (n)
AMP 100 (26) 100 (13) 100 (51) 100 (25)
CL 61.5a (16) 15.4b (2) 5.9b (3) 4.0b (1)
STR 38.5 (10) 23.1 (3) 13.7 (7) 40.0 (10)
TE 38.5c (10) 76.9b (10) 94.1a (48) 56c (14)
Total ( n ) 26 13 51 25
  1. CON; no antibiotics added to supplement, T: chlortetracycline provided as Aureomycin 100-G fed at 11 ppm, TS: chlortetracycline + sulfamethazine, provided as Aureo S-700G (Alpharma Inc.) fed at 44 ppm and V: virginiamycin provided as V-Maxed at 31 ppm.