The Antibacterial Activity of Fragrance Ingredients against Legionella pneumophila

Abstract

In the current study we investigated the antibacterial activity of fragrance ingredients against Legionella pneumophila, a causative agent of severe pneumonia. Among the 41 different fragrance ingredients tested, we found that the natural fragrance ingredients oakmoss (OM) and birch tar oil (BT), which contain many components, exhibit potent antibacterial activity. The minimum inhibitory concentration (MIC, % (v/v)) of OM and BT were 0.0020 and 0.0024, respectively and were lower than that of cinnamic aldehyde (0.0078), which has been previously shown to possess high antimicrobial activity. In a time-kill assay of OM and BT at MIC and two times MIC, the colony forming units (CFU) of the microbe were reduced to between 10 ؊ ؊3 to 10 ؊ ؊4 of the original CFU after 1 h co-incubation. After this time, the CFU gradually decreased in number, but remained above detection levels even after a 48-h co-incubation, except for BT at two times MIC. In contrast, at a concentration of 0.1% OM and BT (approximately 50 times MIC), CFU were not detected after co-incubation for 1 h. Another 18 fragrance ingredients including ketone, aldehyde, lactone, acid, phenol derivative, aliphatic alcohol and quinoline also exhibited a lesser degree of antibacterial activity against L. pneumophila at a MIC of less than 0.10.

The Antibacterial Activity of Compounds Isolated from Oakmoss against <i>Legionella pneumophila</i> and Other <i>Legionella</i> spp.

“…However, neither oakmoss itself nor the 20 individual compounds exhibited antibacterial activity against other Gram-negative and Gram-positive bacteria tested. 6) All Gram-negative bacteria possess an outer membrane that imparts a hydrophilic surface to the cell. Small hydrophilic compounds can traverse the outer membrane through porin proteins that form hydrophilic trans-membrane channels that exclude hydrophobic compounds.…”

“…Samples were serially diluted with BYE-α as described previously. 6) Each diluted sample (50 µL) was mixed with 50 µL of bacterial suspension adjusted to 6.0×10 5 colony forming units (CFU)/mL with BYE-α and incubated at 37°C for 48 h. To determine the MICs against other bacterial strains, bacterial suspensions were adjusted to 1.0×10…”

“…6) The resulting CFU data are expressed as means± standard deviation based on the CFU values obtained from six plates.…”

“…5) We then investigated 41 of these ingredients for antibacterial activity against L. pneumophila. Birch tar oil and oakmoss, both of which are multicomponent ingredients used in natural fragrances, exhibited potent antibacterial activity against L. pneumophila 6) ; however, the chemical structures of the antibacterial components have not been determined.…”

Effects of Oakmoss and Its Components on Biofilm Formation of <i>Legionella pneumophila</i>

“…The antibacterial characteristics of oakmoss and its components have been reported by us previously. 11,12) Specifically, we demonstrated that oakmoss and its components exhibited antibacterial activities against members of the genus Legionella, including clinical and environmental isolates of L. pneumophila and other Legionella spp. 12) In the present study, we investigated the effect of oakmoss and its components on L. pneumophila biofilm formation and the bactericidal activity of oakmoss against the bacterium in biofilms.…”