TABLE 4.
Distribution of ERIC-PCR strains and their antimicrobial resistance phenotypes and genotypes among E. coli strains isolated from broiler chicken flocksa
| ERIC strain | Antimicrobial resistance phenotype | No. of strains with resistance phenotype on:
|
Resistance genotype on:
|
||||
|---|---|---|---|---|---|---|---|
| Farm A | Farm B | Farm C | Farm A | Farm B | Farm C | ||
| A | G T Sp S Su Sf | 5 | 1 | intI1 (aadA) | intI1 (aadA), tetA | ||
| G T Sp S Su | 9 | 2 | 3 | intI1 (aadA) | intI1 (aadA) | intI1 (aadA) | |
| intI1 (aadA), tetA | intI1 (?)b | ||||||
| intI1 (aadA), tetB | |||||||
| G T Su | 1 | intI1 (aadA), tetA | |||||
| G Sp S Su | 3 | 1 | intI1 (aadA), tetA | intI1 (aadA) | |||
| intI1 (aadA) | |||||||
| G Sp S Su | 1 | intI1 (aadA) | |||||
| T Sp S Su Sf | 1 | intI1 (aadA), intI2 | |||||
| T Su | 1 | tetB | |||||
| T S | 1 | 2 | tetB | intI1 (aadA) | |||
| T | 2 | intI2 | |||||
| Sf | 1 | ||||||
| Susceptible | 1 | 2 | |||||
| B | G T Sp S Su Sf | 1 | 1 | intI1 (aadA) | intI1 (aadA), tetB | ||
| G T Sp S Su | 7 | 3 | 1 | intI1 (aadA), tetA | intI1 (aadA), tetA | intI1 (aadA) | |
| intI1 (aadA), intI2, tetA | intI1 (aadA), tetB | ||||||
| intI1 (aadA, dfr), tetA | intI1 (aadA) | ||||||
| G T Sp Su | 1 | intI1 (aadA), tetA | |||||
| C | G T Sp S Su Sf | 1 | 3 | 3 | intI1 (aadA), tetA | intI1 (aadA) | intI1 (aadA) |
| G T Sp S Su | 11 | 7 | 2 | intI1 (aadA), tetA | intI1 (aadA), tetA | intI1 (aadA), intI2 | |
| intI1 (aadA), tetB | intI1 (aadA) | intI1 (aadA) | |||||
| intI1 (aadA) | |||||||
| G Sp S Su | 1 | intI1 (aadA) | |||||
| G Sp Su Sf | 4 | intI1 (aadA) | |||||
| intI1b | |||||||
| A T | 1 | intI1 | |||||
| T S | 2 | intI1 (bla) | |||||
| Sf | 1 | 1 | intI1 (aadA, bla) | ||||
| D | G T Sp S Su Sf | 2 | intI1 (aadA), tetB | ||||
| intI1 (aadA) | |||||||
| G T Sp S Su | 2 | 1 | intI1 (aadA), tetB | intI1 (aadA) | |||
| G Sp S Su Sf | 1 | intI1 (aadA) | |||||
| Sf | 1 | intI1 (aadA) | |||||
Strain types were determined by ERIC-PCR. Class 1 and class 2 integrase genes were detected using DNA-DNA hybridization, and class 1-associated gene cassettes of intI1-positive isolates were screened using PCR-ELISA. The probes were pooled to screen for the presence of β-lactamase (bla), dihydrofolate reductase (dfr), and aminoglycoside resistance (AG) cassettes. The aminoglycoside resistance pool did not contain the aadA1,2 probe. A gene in parentheses following intI1 is an antimicrobial resistance gene present in the integron. The genes listed in parentheses do not reflect the order in the integron or the number of integrons present in the isolates. The abbreviations for antimicrobial resistance are as follows: A, amoxicillin; G, gentamicin; T, tetracycline; Sp, spectinomycin; S, streptomycin; Su, sulfathiazole; and Sf, sarafloxacin.
PCR-ELISA did not detect β-lactamase (bla), dihydrofolate reductase (dfr), or aminoglycoside resistance cassettes in this integron.