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 subculture^a

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

^aGM, 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.