Table 1.
Susceptibility of prototypic and SCV strains and species to TO, FC04–100, GEN or the combination of GEN with one of either steroidal alkaloids
| MIC (μg/mL) | ||||||
|---|---|---|---|---|---|---|
| Species and strains | Auxoa | TO | FC | GEN | GEN + TO (fold)b | GEN + FC (fold)c |
| Staphylococcus ssp. | ||||||
| S. aureus ATCC 29213 | – | > 64 | 8–16 | 0.5 | 0.06 (8) | 0.06–0.12 (4–8) |
| S. aureus ATCC 29213 ΔhemB (SCV) | H | 0.06 | 2 | 8 | – | – |
| S. aureus Newbould | – | > 64 | 8–16 | 0.5 | 0.06 (8) | 0.12 (4) |
| S. aureus Newbould ΔhemB (SCV) | H | 0.06 | 2 | 8 | – | – |
| S. aureus CF07-L | – | > 64 | 8 | 0.5 | 0.06(8) | 0.12 (4) |
| S. aureus CF07-S (SCV) | M | 0.12 | 2 | 8 | – | – |
| S. aureus SH1000 | – | > 64 | 8–16 | 0.5 | 0.06 (8) | 0.06–0.12 (4–8) |
| S. aureus MRSA USA100 ATCC BAA-41 | – | > 64 | 16 | 0.5 | 0.12 (4) | 0.12 (4) |
| S. aureus MRSA USA300 ATCC BAA-1556 | – | > 64 | 16 | 0.5 | 0.06 (8) | 0.06 (8) |
| S. aureus MRSA COL | – | > 64 | 16 | 0.25 | 0.06 (4) | 0.06 (4) |
| S. epidermidis ATCC 12228 | – | > 64 | 8 | 0.5 | 0.12 (4) | 0.12 (4) |
| Bacillus ssp. | ||||||
| B. cereus ATCC 11778 | – | > 64 | 8 | 1 | 0.25 (4) | 0.25 (4) |
| B. cereus ATCC 11778 (SCV#1) | M | 0.03 | 2 | 16 | – | – |
| B. cereus ATCC 11778 (SCV#2) | M | 0.03 | 2 | 16 | – | – |
| B. subtilis ATCC 6333 | – | > 64 | 8 | 0.12 | 0.03 (4) | 0.06 (2) |
| B. subtilis ATCC 6333 (SCV#1) | U | 0.03 | 2 | 2 | – | – |
| B. subtilis ATCC 6333 (SCV#2) | U | 0.03 | 2 | 4 | – | – |
| B. subtilis ATCC 9372 | – | > 64 | 8 | 0.12 | 0.015 (8) | 0.06 (2) |
| B. subtilis ATCC 9372 (SCV#1) | U | 0.03 | 1 | 1 | – | – |
| B. subtilis ATCC 9372 (SCV#2) | U | 0.03 | 1 | 1 | – | – |
| Listeria | ||||||
| L. monocytogenes ATCC 13932 | – | > 64 | 32 | 0.5 | 0.12 (4) | 0.12 (4) |
| L. monocytogenes ATCC 13932 (SCV#1) | U | 0.03 | 1 | > 64 | – | – |
| L. monocytogenes ATCC 13932 (SCV#2) | H | 0.03 | 1 | > 64 | – | – |
Abbreviations: TO tomatidine, FC FC04–100, GEN gentamicin, Auxo auxotrophy, SCV small-colony variant, H hemin, M menadione, T thymidine, U unknown
aFor SCVs, auxotrophism is defined as the requirement of specific compounds in order to regain a normal growth phenotype. An agar diffusion method was used to characterize the auxotrophism of SCVs using H, M or T. If none of these compounds restored normal growth, the auxotrophy was unknown (U)
bGEN was used in combination with TO at a sub-MIC of 8 μg/mL. The fold increase in GEN susceptibility is the ratio of the MIC of GEN used alone vs GEN in the presence of TO
cGEN was used in combination with FC at a sub-MIC of 4 μg/mL. The fold increase in GEN susceptibility is the ratio of the MIC of GEN used alone vs GEN in the presence of FC