Table 3.
Checkerboard analysis with final interactions (best match within triplicate).
| Antimicrobial Agent | Patchouli Oil | Tea Tree Oil | ||||||
|---|---|---|---|---|---|---|---|---|
| MICi | MICc | FIC | ∑FIC [Interaction] |
MICi | MICc | FIC | ∑FIC (Interaction) |
|
| Staphylococcus aureus ATCC 25923 | ||||||||
| oil (% v/v) | 0.25 | 0.008 | 0.032 | 0.282 synergy |
2.5 | 0.08 | 0.032 | 0.282 synergy |
| gentamicin (μg/mL) | 1 | 0.25 | 0.25 | 1 | 0.25 | 0.25 | ||
| oil (% v/v) | 0.125 | 0.125 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.125 | 0.125 | 1 | 0.125 | 0.125 | 1 | ||
| Staphylococcus aureus Sa 1 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.75 additive |
5 | 1.25 | 0.25 | 0.5 synergy |
| gentamicin (μg/mL) | 2 | 1 | 0.5 | 0.5 | 0.125 | 0.25 | ||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 1.0 additive |
5 | 1.25 | 0.25 | 0.375 synergy |
| enrofloxacin (μg/mL) | 8 | 4 | 0.5 | 8 | 1 | 0.125 | ||
| Staphylococcus aureus Sa 2 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.75 additive |
10 | 1.25 | 0.125 | 0.25 synergy |
| gentamicin (μg/mL) | 1 | 0.5 | 0.5 | 0.5 | 0.0625 | 0.125 | ||
| oil (% v/v) | 0.25 | 0.25 | 1 | 2.0 none |
5 | 5 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 4 | 4 | 1 | 4 | 4 | 1 | ||
| Staphylococcus aureus Sa 3 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.5 synergy |
2.5 | 0.625 | 0.25 | 0.5 synergy |
| gentamicin (μg/mL) | 16 | 4 | 0.25 | 8 | 2 | 0.25 | ||
| oil (% v/v) | 0.25 | 0.25 | 1 | 2.0 none |
5 | 5 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 32 | 32 | 1 | 32 | 32 | 1 | ||
| Staphylococcus aureus Sa 4 | ||||||||
| oil (% v/v) | 0.25 | 0.125 | 0.5 | 0.625 additive |
2.5 | 0.32 | 0.128 | 0.253 synergy |
| gentamicin (μg/mL) | 0.5 | 0.0625 | 0.125 | 0.5 | 0.0625 | 0.125 | ||
| oil (% v/v) | 0.25 | 0.25 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.25 | 0.25 | 1 | 0.125 | 0.125 | 1 | ||
| Staphylococcus aureus Sa 5 | ||||||||
| oil (% v/v) | 0.25 | 0.0625 | 0.25 | 0.75 additive |
2.5 | 0.625 | 0.25 | 0.378 synergy |
| gentamicin (μg/mL) | 0.25 | 0.125 | 0.5 | 0.25 | 0.032 | 0.128 | ||
| oil (% v/v) | 0.25 | 0.25 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 1 | 1 | 1 | 0.5 | 0.5 | 1 | ||
| Staphylococcus aureus Sa 6 | ||||||||
| oil (% v/v) | 0.125 | 0.016 | 0.128 | 0.384 synergy |
1.25 | 0.16 | 0.128 | 0.256 synergy |
| gentamicin (μg/mL) | 0.125 | 0.032 | 0.256 | 0.125 | 0.016 | 0.128 | ||
| oil (% v/v) | 0.125 | 0.032 | 0.256 | 0.756 additive |
1.25 | 0.625 | 0.5 | 1.0 additive |
| enrofloxacin (μg/mL) | 0.125 | 0.0625 | 0.5 | 0.125 | 0.0625 | 0.5 | ||
| Staphylococcus aureus Sa 7 | ||||||||
| oil (% v/v) | 0.25 | 0.0625 | 0.25 | 0.506 additive |
1.25 | 0.32 | 0.256 | 0.768 additive |
| gentamicin (μg/mL) | 0.125 | 0.032 | 0.256 | 0.0625 | 0.032 | 0.512 | ||
| oil (% v/v) | 0.125 | 0.0625 | 0.5 | 1.012 additive |
0.625 | 0.625 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.0625 | 0.032 | 0.512 | 0.125 | 0.125 | 1 | ||
| Staphylococcus pseudintermedius ED99 | ||||||||
| oil (% v/v) | 0.25 | 0.032 | 0.128 | 0.192 synergy |
2.5 | 0.32 | 0.128 | 0.256 synergy |
| gentamicin (μg/mL) | 0.5 | 0.032 | 0.064 | 0.5 | 0.064 | 0.128 | ||
| oil (% v/v) | 0.125 | 0.008 | 0.064 | 0.564 additive |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.25 | 0.125 | 0.5 | 0.125 | 0.125 | 1 | ||
| Staphylococcus pseudintermedius Sps 1 | ||||||||
| oil (% v/v) | 0.5 | 0.0625 | 0.125 | 0.375 synergy |
5 | 0.625 | 0.125 | 0.375 synergy |
| gentamicin (μg/mL) | 64 | 16 | 0.25 | 32 | 8 | 0.25 | ||
| oil (% v/v) | 0.25 | 0.016 | 0.064 | 0.564 additive |
1.25 | 0.08 | 0.064 | 0.314 synergy |
| enrofloxacin (μg/mL) | 32 | 16 | 0.5 | 64 | 16 | 0.25 | ||
| Staphylococcus pseudintermedius Sps 2 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.75 additive |
1.25 | 0.16 | 0.128 | 0.378 synergy |
| gentamicin (μg/mL) | 64 | 32 | 0.5 | 32 | 8 | 0.25 | ||
| oil (% v/v) | 0.25 | 0.016 | 0.064 | 0.564 additive |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 64 | 32 | 0.5 | 64 | 64 | 1 | ||
| Staphylococcus pseudintermedius Sps 3 | ||||||||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 0.625 additive |
1.25 | 0.16 | 0.128 | 0.191 synergy |
| gentamicin (μg/mL) | 128 | 16 | 0.125 | 64 | 4 | 0.0625 | ||
| oil (% v/v) | 0.5 | 0.032 | 0.064 | 0.564 additive |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 64 | 32 | 0.5 | 64 | 64 | 1 | ||
| Staphylococcus pseudintermedius Sps 4 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.5 synergy |
0.625 | 0.16 | 0.256 | 0.381 synergy |
| gentamicin (μg/mL) | 64 | 16 | 0.25 | 32 | 4 | 0.125 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 32 | 32 | 1 | 64 | 64 | 1 | ||
| Staphylococcus pseudintermedius Sps 5 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.5 synergy |
5 | 1.25 | 0.25 | 0.281 synergy |
| gentamicin (μg/mL) | 256 | 64 | 0.25 | 128 | 4 | 0.031 | ||
| oil (% v/v) | 0.5 | 0.032 | 0.064 | 0.564 additive |
1.25 | 0.625 | 0.5 | 1.0 additive |
| enrofloxacin (μg/mL) | 64 | 32 | 0.5 | 64 | 32 | 0.5 | ||
| Staphylococcus pseudintermedius Sps 6 | ||||||||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 0.75 additive |
2.5 | 0.32 | 0.128 | 0.159 synergy |
| gentamicin (μg/mL) | 128 | 32 | 0.25 | 64 | 2 | 0.031 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
2.5 | 2.5 | 1 | 3.0 none |
| enrofloxacin (μg/mL) | 32 | 32 | 1 | 64 | 128 | 2 | ||
| Staphylococcus pseudintermedius Sps 7 | ||||||||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 1 additive |
0.625 | 0.16 | 0.256 | 0.381 synergy |
| gentamicin (μg/mL) | 128 | 64 | 0.5 | 32 | 4 | 0.125 | ||
| oil (% v/v) | 0.5 | 0.008 | 0.016 | 0.516 additive |
1.25 | 0.625 | 0.5 | 1.0 additive |
| enrofloxacin (μg/mL) | 64 | 32 | 0.5 | 128 | 64 | 0.5 | ||
| Staphylococcus pseudintermedius Sps 8 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.75 additive |
1.25 | 0.16 | 0.128 | 0.191 synergy |
| gentamicin (μg/mL) | 128 | 64 | 0.5 | 64 | 4 | 0.0625 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 64 | 64 | 1 | 64 | 64 | 1 | ||
| Staphylococcus pseudintermedius Sps 9 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.375 synergy |
5 | 1.25 | 0.25 | 0.375 synergy |
| gentamicin (μg/mL) | 64 | 8 | 0.125 | 32 | 4 | 0.125 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.125 | 0.125 | 1 | 0.125 | 0.125 | 1 | ||
| Staphylococcus pseudintermedius Sps 10 | ||||||||
| oil (% v/v) | 0.5 | 0.125 | 0.25 | 0.506 additive |
1.25 | 0.32 | 0.256 | 0.512 additive |
| gentamicin (μg/mL) | 0.125 | 0.032 | 0.256 | 0.0625 | 0.016 | 0.256 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 64 | 64 | 1 | 32 | 32 | 1 | ||
| Staphylococcus pseudintermedius Sps 11 | ||||||||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 0.75 additive |
2.5 | 0.625 | 0.25 | 0.378 synergy |
| gentamicin (μg/mL) | 0.5 | 0.125 | 0.25 | 0.125 | 0.016 | 0.128 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
0.625 | 0.625 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.125 | 0.125 | 1 | 0.125 | 0.125 | 1 | ||
| Staphylococcus pseudintermedius Sps 12 | ||||||||
| oil (% v/v) | 0.5 | 0.25 | 0.5 | 0.75 additive |
5 | 1.25 | 0.25 | 0.5 synergy |
| gentamicin (μg/mL) | 32 | 8 | 0.25 | 8 | 2 | 0.25 | ||
| oil (% v/v) | 0.5 | 0.5 | 1 | 2.0 none |
1.25 | 1.25 | 1 | 2.0 none |
| enrofloxacin (μg/mL) | 0.5 | 0.5 | 1 | 0.5 | 0.5 | 1 | ||
Sa—Staphylococcus aureus; Sps—Staphylococcus pseudintermedius; MICi: MIC individually as MIC(O) or MIC(A); MICc: MIC in combination as MIC(OxA) or MIC(AxO); FIC: fractional inhibitory concentrations; none = noninteractive.