Table 4.
Isolate level effect of antimicrobial treatment of calves on prevalence of nonsusceptible Escherichia coli
| Antimicrobial treatment | Age1
|
Class2 | Enrofloxacin treatment3
|
Ceftiofur treatment3
|
||||||
|---|---|---|---|---|---|---|---|---|---|---|
| P-value | Tx, % (n = 152) | NoTx, % (n = 1,271) | P-value | Odds ratio4 | Tx, % (n = 144) | NoTx, % (n = 1,279) | P-value | Odds ratio4 | ||
| Ceftriaxone | 0.0002 | S | 34 | 40 | 0.3 | 3 | 43 | 0.08 | ||
| NS | 66 | 60 | 0.8 (0.5–1) | 97 | 57 | 3 (0.9–12) | ||||
| Neomycin | <0.0001 | S | 65 | 68 | 0.7 | 62 | 68 | 0.05 | ||
| NS | 35 | 32 | 0.9 (0.6–1) | 38 | 32 | 0.5 (0.3–1) | ||||
| Ciprofloxacin | 0.0003 | S | 80 | 97 | 0.005 | 98 | 95 | 0.31 | ||
| NS | 20 | 3 | 2.0 (1–4) | 2 | 5 | 4 (0.3–58) | ||||
| Nalidixic acid | <0.0001 | S | 73 | 96 | <0.0001 | 94 | 94 | 0.08 | ||
| NS | 27 | 4 | 3.0 (2–6) | 6 | 6 | 6 (0.8–42) | ||||
1
Categorical age group variable with animals grouped by age in days: 3 to 14 d (AGE-1), 15 to 35 d (AGE-2), and 36 to 65 d (AGE-3).
2
S = susceptible; NS = nonsusceptible.
3
E. coli from a calf with a farm record of treatment at least once with the referred antimicrobial drug from birth to rectal swab sampling (Tx) or from a calf with a farm record showing no treatment with the referred antimicrobial drug from birth to rectal swab sampling (NoTx).
4
Odds ratio for isolation of a nonsusceptible E. coli in the drug-treated group compared with the not-treated group. The 95% confidence interval is in parentheses.