TABLE 5.
Patterns of encoded genetic determinants in tetracycline-resistanta E. coli isolated from fecal deposits of steers fed antimicrobial agents
| Gene profile | Detection of gene |
No. (%) of isolates within treatment groupb |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| tetA | tetB | tetC | sul1 | sul2 | blaTEM1 | A44 | AS700 | Control | Overall | |
| G1T | + | − | − | − | − | + | 1 (1.3) | 0 (0) | 0 (0) | 1 (0.4) |
| G2T | + | + | − | − | + | − | 0 (0) | 0 (0) | 1 (1.4) | 1 (0.4) |
| G3T | + | − | − | + | − | + | 30 (38.0) | 1 (1.2) | 0 (0) | 31 (13.3) |
| G4T | + | + | − | + | + | + | 3 (3.8) | 0 (0) | 0 (0) | 3 (1.3) |
| G5T | − | + | − | − | − | − | 0 (0) | 2 (2.4) | 10 (14.1) | 12 (5.2) |
| G6T | − | + | − | − | + | − | 41 (51.9) | 48 (57.8) | 60 (80.0) | 149 (62.9) |
| G7T | − | + | + | − | + | − | 0 (0) | 0 (0) | 1 (1.4) | 1 (0.4) |
| G8T | − | + | − | + | + | − | 0 (0) | 0 (0) | 1 (1.4) | 1 (0.4) |
| G9T | − | − | + | − | − | − | 0 (0) | 10 (12.0) | 0 (0) | 10 (4.3) |
| G10T | − | − | + | − | + | − | 0 (0) | 18 (21.7) | 0 (0) | 18 (7.7) |
| G11T | − | − | − | − | + | − | 2 (2.5) | 0 (0) | 0 (0) | 2 (0.9) |
| G12T | − | − | − | − | − | − | 2 (2.5) | 4 (4.8) | 1 (1.4) | 7 (3.0) |
| Total | 79 | 83 | 75 | 237 | ||||||
a
E. coli was isolated using MacConkey agar amended with tetracycline (16 μg ml−1), and fecal material was sampled from deposits on six occasions over 175 days, representing short, moderate, and long periods of environmental exposure.
b
Control, no antimicrobial agents added to the diet; the A44 and AS700 antimicrobial feeding treatments are defined in Materials and Methods.