Activity and mechanisms of action of selected biocidal agents on Gram-positive and -negative bacteria.
OBJECTIVE
This study investigates the antimicrobial activity and mode of action of two natural products, eugenol and thymol, a commonly utilized biostatic agent, triclocarban (TCC), and two surfactants, didecyldimethylammonium chloride (DDDMAC) and C10-C16 alkyldimethyl amine N-oxides (ADMAO).


RESULTS
Methods used included: determination of minimum inhibitory concentrations (MICs), lethal effect studies with suspension tests and the investigation of sub-MIC concentrations on growth of E. coli, Staph. aureus and Ps. aeruginosa using a Bioscreen microbiological analyser. Leakage of intracellular constituents and the effects of potentiating agents were also investigated. Only DDDMAC was bactericidal against all of the organisms tested. Eugenol, thymol and ADMAO showed bacteriostatic and bactericidal activity, but not against Ps. aeruginosa. TCC was only bacteristatic against Staph. aureus, but like the other agents, it did affect the growth of the other organisms in the Bioscreen experiments. All of the antimicrobial agents tested were potentiated by the permeabilizers to some extent and leakage of potassium was seen with all of the agents except TCC.


CONCLUSIONS
DDDMAC was bactericidal against all organisms tested and all compounds had some bacteriostatic action. Low level static effects on bacterial growth were seen with sub-MIC concentrations. Membrane damage may account for at least part of the mode of action of thymol, eugenol, DDDMAC and ADMAO.


CONCLUSIONS
The ingredients evaluated demonstrated a range of bactericidal and bacteriostatic properties against the Gram-negative and -positive organisms evaluated and the membrane (leakage of intracellular components) was implicated in the mode of action for most (except TCC). Sub-MIC levels of all ingredients did induce subtle effects on the organisms which impacted bacterial growth, even for those which had no true inhibitory effects.
Walsh
S E
SE
Leicester School of Pharmacy, De Montfort University, Leicester, LE1 9BH, UK. swalsh@dmu.ac.uk
Maillard
J-Y
JY
Russell
A D
AD
Catrenich
C E
CE
Charbonneau
D L
DL
Bartolo
R G
RG
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002224:Carbanilides / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D005054:Eugenol / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods; D011188:Potassium / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012717:Sesquiterpenes / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000254:growth & development; D013501:Surface-Active Agents / Q000494:pharmacology; D013943:Thymol / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002224:Carbanilides; D000644:Quaternary Ammonium Compounds; D012717:Sesquiterpenes; D013501:Surface-Active Agents; D013943:Thymol; D005054:Eugenol; D004492:Edetic Acid; C009540:triclocarban; C037055:nerolidol; D011188:Potassium; C027118:didecyldimethylammonium