Table II.
Prevalences of resistance to at least one of 21 antimicrobials tested among fecal Escherichia coli from pigs on farms that used in-feed antimicrobial medication and those that did not
| Group (Number of isolates) | Farm medication group/Pig-age group | Number of farms | Number of isolates per category | Prevalence of resistance to at least one antimicrobial among isolates (%) |
|---|---|---|---|---|
| Antimicrobial use (940) | Use in-feed medication | 34 | 680 | 68.19a |
| No in-feed medication | 13 | 260 | 21.81 | |
| Age of pigs (940) | Weaner pigs | 47 | 470 | 46.70b |
| Finisher pigs | 47 | 470 | 43.30 |
a
Significantly greater (P < 0.0001; Fisher’s Exact Test) than prevalence from no in-feed medication farms.
b
Significantly greater (P = 0.0001; Fisher’s Exact Test) than prevalence from finisher pigs.