TABLE 1.
Effect of cessation of in ovo administration of ceftiofur and replacement with lincomycin-spectinomycin on the proportion of non-enriched samples from newly hatched, broiler, and breeder birds with E. coli isolates positive for ESBL/AmpC resistance genes
| Sample origin | Before or after ceftiofur cessation in broiler | Antimicrobial(s) administered in ovo | No. of samples (no. of isolates)a | % of samples with one or more isolates positive for: |
||
|---|---|---|---|---|---|---|
| blaTEM | blaCMY-2b | blaCTX-M | ||||
| Meconium of newly hatched chicks | Before (2014) | Ceftiofur | 20 (96) | 45 | 90A | 20 |
| After (2015) | None | 14 (69) | 71 | 36B | 0 | |
| After (2015) | Lincomycin-spectinomycin | 16 (80) | 56 | 50B | 0 | |
| Pooled feces of broilers | Before (2014) | Ceftiofur | 20 (100) | 50 | 60 | 5 |
| After (2015) | None | 14 (70) | 43 | 50 | 0 | |
| After (2015) | Lincomycin-spectinomycin | 16 (79) | 69 | 44 | 6 | |
| Pooled feces of breeders | Before (2014) | Ceftiofur | 22 (109) | 64 | 0 | 0 |
| Before (2015) | Ceftiofur | 24 (119) | 60 | 16 | 0 | |
a
All isolates tested were uidA positive (likely E. coli).
b
Different letters in the same column of results for genes and same sample origin indicate significantly different results.