International Journal of Antimicrobial Agents 2006-01-01

In vitro activity of lauric acid or myristylamine in combination with six antimicrobial agents against methicillin-resistant Staphylococcus aureus (MRSA).

Takashi Kitahara, Yuko Aoyama, Yoichi Hirakata, Shimeru Kamihira, Shigeru Kohno, Nobuhiro Ichikawa, Mikiro Nakashima, Hitoshi Sasaki, Shun Higuchi

Index: Int. J. Antimicrob. Agents 27(1) , 51-7, (2006)

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Abstract

The objective of this study was to investigate the in vitro activities of lauric acid and myristylamine in combination with six antimicrobial agents against methicillin-resistant Staphylococcus aureus (MRSA). The combination effect of lipids and antimicrobial agents was evaluated by the checkerboard method to obtain a fractional inhibitory concentration (FIC) index. The effects of lauric acid + gentamicin (GM) and lauric acid + imipenem (IPM) combinations were synergistic against the clinical isolates in 12 combinations. An antagonistic FIC index was observed only with the myristylamine + GM combination. We investigated in detail the antimicrobial activity for two combinations that showed a synergistic effect. The cytotoxicity of lauric acid was not enhanced by the addition of GM and IPM. In time-kill studies, lauric acid + GM and lauric acid + IPM combinations at one-eighth of the minimum inhibitory concentration produced a bacteriostatic effect.