Surfactants as Microbicides and Contraceptive Agents: A Systematic In Vitro Study

BACKGROUND: The urgent need for cheap and easy-to-use protection against both unwanted pregnancies and sexually transmitted diseases has stimulated considerable interest in the use of surfactants as microbicides anti-viral and contraceptive agents in recent years. In the present study we report a systematic in vitro evaluation of the microbicidal anti-viral and contraceptive potential of cationic anionic zwitterionic and non-ionic surfactants. METHODOLOGY/PRINCIPAL FINDINGS: Toxicity was evaluated in mammalian columnar epithelial (MDCK) cells human sperm cells Candida albicans Escherichia coli Pseudomonas aeruginosa Neisseria gonorrhoeae Streptococcus agalactiae and Enterococcus faecalis. The inhibition of adenovirus and lentivirus infection of MDCK cells was also tested. A homologous series of cationic surfactants alkyl-NNN-trimethylammonium bromides (C(n)TAB) with varying alkyl chains were shown to be bactericidal and fungicidal at doses that were related to the surfactant critical micelle concentrations (CMC) all of them at concentrations significantly below the CMC. In general bacteria were more susceptible to this surfactant group than C. albicans and this organism in turn was more susceptible than MDCK cells. This suggests that the C(n)TAB may be useful as vaginal disinfectants only in so far as bacterial and fungal infections are concerned. None of the surfactants examined including those that have been used in pre-clinical studies showed inhibition of adenovirus or lentivirus infection of MDCK cells or spermicidal activity at doses that were sub-toxic to MDCK cells. CONCLUSIONS/SIGNIFICANCE: The results of this study lead us to propose that systematic analysis of surfactant toxicity such as we report in the present work be made a mandatory pre-condition for the use of these substances in pre-clinical animal and/or human studies.