Article Figures & Data
Tables
- Table 1
Frequencies of single-step antibiotic-resistant mutants occurring in the presence and absence of tea tree oila
Organism and no. of isolates Antibiotic Fold increase in MIC Frequency of mutants in: P valueb Control culture with: TTO culture with: Antibiotic alone (treatment A) Antibiotic + TTO (treatment B) Antibiotic alone (treatment C) Antibiotic + TTO (treatment D) S. aureus 10 RIF 8 8.9 × 10−8 5.9 × 10−8 1.1 × 10−7 7.2 × 10−8 0.0065c 10 MUP 8 7.3 × 10−8 2.3 × 10−8 9.9 × 10−8 3.5 × 10−8 0.0002d 7 VAN 2 2.4 × 10−7 1.2 × 10−7 3.4 × 10−7 5.9 × 10−7 0.1268 4 CIP 2 8.1 × 10−8 5.9 × 10−8 8.6 × 10−8 3.7 × 10−8 0.6725 E. coli 10 RIF 8 3.7 × 10−8 2.9 × 10−8 4.3 × 10−8 3.8 × 10−8 0.2083 9 KAN 2 3.3 × 10−6 2.0 × 10−7 2.6 × 10−6 3.1 × 10−7 <0.0001e ↵a Values are the geometric means from 4 to 10 isolates. MUP, mupirocin; RIF, rifampin; VAN, vancomycin; CIP, ciprofloxacin; KAN, kanamycin; TTO, tea tree oil.
↵b P values were obtained by repeated-measure one-way ANOVA.
↵c Significant differences exist between treatments B and C (P < 0.01) (Bonferroni post test).
↵d Significant differences exist between treatments A and B (P < 0.01), B and C (P < 0.001), and C and D (P < 0.05).
↵e Significant differences exist between treatments A and B (P < 0.001), A and D (P < 0.01), B and C (P < 0.001), and C and D (P < 0.01).
- Table 2
S. aureus MICs of antibiotics (μg/ml) alone, antibiotics with or without tea tree oil (0.062%) or terpinen-4-ol (0.031%), and tea tree oil or terpinen-4-ol without antibiotic, determined by serial subculturea
Agent (no. of isolates) and parameter Treatment MIC on day: 1 2 3 4 5 6 CIP (10) Median Alone 0.5 1 1 2 2 2 With TTO 0.25 1 1 2 2 2 With T4ol 0.25 0.5 1 2 2 2 GM Alone 0.8 0.8 1.1 1.5 1.6 2.3 With TTO 0.25 1.0 1.1 1.6 2.5 3.5 With T4ol 0.2 0.6 1.0 1.5 1.7 2.3 MUP (11) Median Alone 0.12 0.25 0.5 1 1 1 With TTO 0.12 0.12 0.5 0.5 0.5 1 With T4ol 0.12 0.12 0.5 1 4 2 GM Alone 0.1 0.3 0.5 0.9 1.2 1.5 With TTO 0.1 0.2 0.5 0.6 0.5 1.4 With T4ol 0.1 0.2 0.5 0.9 1.9 3.1 VAN (12) Median Alone 1 2 4 8 4 4 With TTO 1 4 4 8 4 4 With T4ol 1 4 4 8 4 4 GM Alone 1.0 2.7 4.5 7.6 4.0 3.8 With TTO 1.1 5.0 5.0 6.3 3.8 4.3 With T4ol 0.9 4.0 4.0 9.5 3.6 5.0 Tea tree oil (18) Median Alone 0.5 0.5 1 1 1 2 GM Alone 0.5 0.7 1.0 0.9 1.0 1.7 Terpinen-4-ol (18) Median Alone 0.25 0.25 0.25 0.5 0.5 1 GM Alone 0.2 0.3 0.3 0.6 0.6 0.8 ↵a GM, geometric means. Boldface type indicates that the MIC is more than double the baseline (day 1) value. Single underlining indicates that values differed significantly from antibiotic alone on that day. Double underlining indicates significant differences between tea tree oil and terpinen-4-ol treatments on that day.
- Table 3
Summary of E. coli MICs of antibiotics (μg/ml) alone, antibiotics with tea tree oil (0.062%) or terpinen-4-ol (0.031%), and tea tree oil or terpinen-4-ol without antibiotics, determined by serial subculturea
Agent (no. of isolates) and parameter Treatment MIC on day: 1 2 3 4 5 6 CIP (12) Median Alone 0.008 0.016 0.016 0.03 0.03 0.12 With TTO 0.008 0.016 0.03 0.06 0.06 0.12 With T4ol 0.008 0.016 0.06 0.06 0.12 0.12 GM Alone 0.010 0.025 0.034 0.070 0.070 0.140 With TTO 0.007 0.014 0.029 0.045 0.064 0.122 With T4ol 0.009 0.018 0.048 0.078 0.100 0.147 KAN (11) Median Alone 8 32 16 64 64 128 With TTO 4 16 32 32 32 64 +With T4ol 4 16 32 32 32 64 GM Alone 6.7 45.3 20.2 60.4 50.8 107.6 With TTO 4.8 12.7 33.9 38.1 42.7 47.9 With T4ol 2.5 15.1 28.5 33.9 32.0 53.8 AMP (10) Median Alone 2 4 8 8 16 16 With TTO 2 4 8 8 16 16 With T4ol 2 4 8 8 16 32 GM Alone 2.1 4.9 8.0 10.6 11.3 16.0 With TTO 2.1 4.6 8.6 9.8 12.1 12.1 With T4ol 2.1 4.9 11.3 11.3 17.1 24.3 Tea tree oil (18) Median Alone 0.5 1 1 1 1 1 GM Alone 0.65 0.73 0.96 1.00 1.12 0.96 Terpinen-4-ol (18) Median Alone 0.12 0.25 0.25 0.25 0.25 0.25 GM Alone 0.13 0.17 0.22 0.29 0.25 0.26 ↵a GM, geometric means. Boldface type indicates that the MIC is more than double the baseline (day 1) value. Single underlining indicates that values differed significantly from antibiotic alone on that day. Double underlining indicates significant differences between tea tree oil and terpinen-4ol treatments on that day.
- Table 4
MICs of antibiotics (μg/ml), biocides (μg/ml), and tea tree oil and terpinen-4-ol (%, vol/vol) for three Staphylococcus strains serially subcultured with terpinen-4-ol or tea tree oila
Agent S. aureus NCTC 6571 S. aureus ATCC 25923 S. epidermidis ATCC 12228 Passage no. MIC Passage no. MIC Passage no. MIC Control With 0.1% T4ol Control With 0.1% T4ol With 0.1% TTO Control With 0.2% T4ol AMX 19 0.12 0.06 18 0.12 0.12 0.12 14 1 0.5 22 0.25 0.25 20 0.5 0.25 17 1 0.5 CIP 17 0.25 0.06 16 0.12 0.12 0.25 14 0.25 0.25 19 0.12 0.06 18 0.25 0.06 0.12 17 0.5 0.25 22 0.12 0.06 20 0.25 0.06 GEN 17 1 2 16 0.5 0.25 0.5 14 0.12 0.5 19 1 1 18 0.25 0.12 0.12 17 0.25 0.25 22 1 2 20 0.25 0.25 TET 17 0.12 0.06 16 0.12 0.12 0.25 14 0.5 0.5 19 0.25 <0.03 18 0.25 0.12 0.25 17 1 0.5 22 0.12 0.06 20 0.25 0.12 VAN 17 1 1 16 2 2 2 14 4 4 19 1 0.5 18 1 1 2 17 4 4 22 0.5 0.25 20 1 1 Benzalkonium 17 0.5 1 16 2 0.5 2 14 2 1 Chloride 19 1 1 18 2 0.5 1 17 2 1 22 1 1 20 2 0.5 Triclosan 19 0.06 0.03 18 0.06 0.03 0.03 17 0.03 0.06 22 0.12 0.12 20 0.25 0.12 Tea tree oil 17 0.5 0.25 16 0.12 0.25 0.25 14 0.5 0.5 19 1 0.5 18 0.5 0.5 0.5 17 0.5 0.5 22 0.25 0.25 20 0.5 0.5 Terpinen-4-ol 17 0.25 0.5 16 0.25 0.5 0.5 14 0.5 0.5 19 0.5 0.5 18 0.5 0.5 0.25 17 0.5 0.5 22 0.12 0.25 20 0.12 0.25 ↵a Boldface type indicates a difference in MIC of 4-fold or more for passaged and nonpassaged strains.
