Table 1.
Tetracycline resistance profiles of clostridial isolates
| Isolate | MIC (mg/L) | ||
|---|---|---|---|
| Tetracycline | Minocycline | Doxycycline | |
| P. sordellii | |||
| TetS isolates (n = 18) | < 0.125 | < 0.047 | < 0.047 |
| SSCC37615 | 8 | 1.5 | 1.5–3 |
| SSCC18838 | 8–16 | 1.5–3 | 1.5–3 |
| SSCC18392 | 8–16 | 3 | 3 |
| SSCC32135 | 8 | 1.5 | 1.5–3 |
| UMC2 | < 0.125 | < 0.047 | 0.094 |
| R28058 | 32 | 6 | 6 |
| C. perfringens | |||
| JIR4 (+ control) | 8–16 | 1.5–3 | 3 |
| JIR325 (− control) | < 0.125 | < 0.047 | 0.094 |
| C. difficile | |||
| 630 (+ control) | > 32 | 12 | N/A |
| CD37 (− control) | < 0.125 | < 0.094 | N/A |
| MCD43 | 4 | 0.375 | N/A |
| MCD46 | 2–4 | 0.375 | N/A |
Displayed is the MIC value (in mg/L) determined for tetracycline, minocycline and doxycycline using a microdilution method across two independent experiments for C. difficile and three for the other species. If different values were determined for MICs between experiments they are represented as a range between those values. Clostridial isolates are listed with their species and isolate name. TetS isolates refers to the remaining 18 isolates of P. sordellii tested that all displayed sensitivity to the lowest concentration of each antibiotic tested (see Additional file 2: Table S2)