TABLE 3.
Association of tetracycline resistance with plasmids, transposons, and other resistance genes
| Tcr operon class | No. of isolates | No. of isolates with:
|
Tcr operon on transposon | Other resistance genes detected in transposon | Replication of Tcr plasmid in E. coli JM109d | Phenotype of E. coli transformantse | |
|---|---|---|---|---|---|---|---|
| Tcr operons detected on plasmids | Tn5393 detected on Tcr plasmid | ||||||
| B | 18 | 7a | 7 | Tn10(n = 18) | None | 7/7 | Tcr |
| A | 10 | 10 | 10 | Tn1720(n = 10) | None | 3/10 | Tcr |
| C | 9 | 9 | 8 | Tn1404(n = 9) | aadA2, sulI | 4/9 | Tcr Sulr |
| Gb | 4 | 4 | 4 | Unknown | 0/4 | ||
| Gc | 1 | 1 | 1 | Unknown | 1/1 | Tcr | |
a
The presence of Tet B on plasmids in the remaining 11 isolates could not be confirmed due to poor plasmid integrity in preparations from these isolates.
b
Variant found in isolates R36, R57, R67, and R82.
c
Variant found in isolate R121A.
d
Number of plasmids which were replicated/total number of plasmids tested.
e
Transformants were tested for growth on oxytetracycline, streptomycin, sulfathiazole, ampicillin, gentamicin, kanamycin, trimethoprim, cefoxitin, cefotaxime, cephalothin, piperacillin, and ciprofloxacin. Unless otherwise indicated, isolates were sensitive to the antibiotics.