Table 4.
Tetracycline resistance genotypes of fecal bacteria from organically raised and feral swinea
| Swine origin | Tetracycline resistance gene class | No. of isolates tested | Taxonomic affiliation |
|---|---|---|---|
| Organic | Unk | 2 | Actinobacteria-Bifidobacteriales |
| farm | Unk | 6 | Firmicutes-Selenomonadales |
| tet(A) | 4 | Proteobacteria-Enterobacteriaceae, Escherichia coli | |
| tet(B) | 3 | Proteobacteria-Enterobacteriaceae, Escherichia coli | |
| tet(L) | 3 | Firmicutes-Streptococcaceaeb | |
| tet(M) | 1 | Firmicutes-Streptococcaceae | |
| tet(O) | 1 | Firmicutes-Streptococcaceae | |
| tet(O) | 9 | Firmicutes-Clostridiales | |
| tet(O) | 3 | Firmicutes-Selenomonadales | |
| tet(O) | 1 | Firmicutes-Selenomonadales, Megasphaera elsdenii | |
| tet(OW) | 8 | Firmicutes-Selenomonadales, Megasphaera elsdenii | |
| tet(OWO) | 11 | Firmicutes-Selenomonadales, Megasphaera elsdenii | |
| tet(W) | 2 | Firmicutes-Selenomonadales, Megasphaera elsdenii | |
| tet(W) | 4 | Firmicutes-Selenomonadales | |
| tet(W) | 4 | Firmicutes-Clostridiales | |
| tet(W) | 2 | Firmicutes-Erysipelotrichaceae | |
| tet(W) | 7 | Firmicutes-Lactobacillaceae | |
| tet(W) | 5 | Actinobacteria-Coriobacteriaceae | |
| tet(W) | 1 | Fusobacteria-Fusobacteriales | |
| tet(Q) | 5 | Bacteroidetes/Chlorobi- Bacteroidales | |
| Feral | Unk | 3 | Firmicutes-Lactobacillaceae |
| tet(M) | 1 | Firmicutes-Streptococcaceae | |
| tet(O) | 17 | Firmicutes-Streptococcaceae | |
| tet(B) | 3 | Proteobacteria-Enterobacteriaceae, Escherichia coli | |
| tet(W) | 2 | Firmicutes-Clostridiales | |
| tet(W) | 2 | Proteobacteria-Desulfovibrionales |
Tetracycline resistance gene class was determined from PCR assays. Unk, unknown, isolate was negative for all PCR assays. Except for E. coli and M. elsdenii, fecal bacteria were selectively isolated on RTC agar plus 64 μg CTC/ml (Table 1) and differentiated from each other based on rrs-V3 sequences. E. coli isolates were obtained from MacConkey agar medium plus 16 or 64 μg CTC/ml (Table 2). Megasphaera elsdenii isolates were selected from colonies able to grow on PYG agar medium containing 64 μg CTC/ml (Table 2) and include previously described strains (19).
One Streptococcaceae isolate was positive in PCR assays for both tet(L) and tet(O) genes, and a second isolate was positive for both tet(L) and tet(M) genes.