Antimicrobial and synergistic effects of lemongrass and geranium essential oils against Streptococcus mutans, Staphylococcus aureus, and Candida spp.

Table 1 Minimum microbicidal concentration values of Cymbopogon schoenanthus (lemongrass) and Pelargonium graveolens (geranium) essential oils against Streptococcus mutans, Staphylococcus aureus, Candida albicans, C. krusei, and C. dubliniensis

Microorganism	Cymbopogon schoenanthus	Pelargonium graveolens
Streptococcus mutans	16	16
Staphylococcus aureus	4	4
Candida albicans	0.06	0.06
Candida krusei	0.06	0.03
Candida dubliniensis	0.03	0.06

Data are minimum microbicidal concentration (%).

Table 2 Minimum microbicidal concentration values of isolated essential oils, and synergistic and additive combinations of Cymbopogon schoenanthus and Pelargonium graveolens essential oils against Staphylococcus aureus

Combination	Individual MMC values (%)				Combined concentrations (%)		FICI	MMC reduction		Effect
	LE		GE		LE	GE		LE	GE
C. + P.	4		4		2	0.5	0.62	2 ×	8 ×	Additive
C. + P.					2	0.25	0.56	2 ×	16 ×	Additive
C. + P.					2	0.12	0.53	2 ×	33 ×	Additive
C. + P.					1	0.06	0.26	4 ×	66 ×	Synergistic

C.: Cymbopogon schoenanthus; FICI: Fractional inhibitory concentration index; GE: Pelargonium graveolens; LE: Cymbopogon schoenanthus; MMC: Minimum microbicidal concentration; P.: Pelargonium graveolens.