Table 2.
Chloretracycline-resistant E. coli populations in fecal samples from organically raised and feral swinea
| Swine origin |
E. coli population at chlortetracycline concn (μg/ml): |
||
|---|---|---|---|
| 0 | 16 | 64 | |
| Organically raised | 6.1 × 106 | 4.9 × 106 (73%) (A) | 1.9 × 106 (28%) (B) |
| Feral | 2.0 × 107 | <LOD (<.03%) (A) | <LOD (<.03%) (B) |
Values in the table are the average cultivable populations (expressed as CFU/g [wet weight] of feces) of lactose-fermenting bacteria cultured aerobically on MacConkey agar plates containing lactose (spread plate method). E. coli populations in 10 organically raised swine (6.1 × 106) were not significantly different (P > 0.1, CI = 95%, Welch's t test) from those of 19 feral swine (2.0 × 107). Values in parentheses represent chlortetracycline-resistant E. coli CFU expressed as percentages of total cultivable E. coli bacteria for each animal group. Percent values with the same uppercase letters in parentheses (A and B) were significantly different (P < 0.001, CI = 95%, Welch's t test). The limit of detection (LOD) was 5 × 103 CFU/g feces for medium containing chlortetracycline.