TABLE 4.
Patterns of encoded genetic determinants in ampicillin-resistanta E. coli strains 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 | |
| G1A | + | − | − | − | − | + | 3 (5.4) | 0 (0) | 5 (10.4) | 8 (5.0) |
| G2A | + | − | − | + | − | + | 34 (60.7) | 7 (12.5) | 0 (0) | 41 (25.6) |
| G3A | + | − | − | − | + | + | 0 (0) | 0 (0) | 1 (2.1) | 1 (0.6) |
| G4A | + | − | + | + | − | + | 0 (0) | 1 (1.8) | 0 (0) | 1 (0.6) |
| G5A | + | − | − | + | + | + | 5 (8.9) | 0 (0) | 0 (0) | 5 (3.1) |
| G6A | − | + | − | − | + | − | 0 (0) | 3 (5.4) | 7 (14.6) | 10 (6.3) |
| G7A | − | + | − | + | + | − | 0 (0) | 1 (1.8) | 0 (0) | 1 (0.6) |
| G8A | − | − | + | − | − | − | 9 (16.1) | 38 (67.9) | 9 (18.4) | 56 (34.8) |
| G9A | − | − | + | − | + | − | 1 (1.8) | 3 (5.4) | 0 (0) | 4 (2.5) |
| G10A | − | − | − | + | − | − | 0 (0) | 0 (0) | 1 (2.1) | 1 (0.6) |
| G11A | − | − | − | − | + | − | 1 (1.8) | 1 (1.8) | 0 (0) | 2 (1.3) |
| G12A | − | − | − | − | − | + | 2 (3.6) | 0 (0) | 5 (10.4) | 7 (4.4) |
| G13A | − | − | − | − | − | − | 1 (1.8) | 2 (3.6) | 21 (43.8) | 24 (15.0) |
| Total | 56 | 56 | 49 | 161 | ||||||
a
E. coli was isolated using MacConkey agar amended with ampicillin (32 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.