New thiol derivatives containing a quaternary ammonium group bearing variable hydrocarbon chains via an amide connector or not between the sulphur and nitrogen atoms were synthesised with the future aim to be grafted on metal surfaces for obtaining contact-active auto-bactericidal surfaces. Their biostatic and bactericidal activities were evaluated against four microbial strains (Pseudomonas aeruginosa, Staphylococcus aureus, Aspergillus niger and Candida albicans). The presence of the thiol and amide functions in these surfactants was discussed in relation with the antimicrobial activity along with the influence of the length of alkyl chains in order to determine which molecular parameters are 'critical' for biological activity, and consequently what molecules must be chosen for grafting on metal surface.