Fig. 1.

Chemical structures of antimicrobial compounds used in this study. Ampicillin served as standard for solutes whose uptake is porin mediated. Formaldehyde-releasing biocides (MBO and HHT) are commonly used for technical preservations. Kathon 893 (octylisothiazolinone) and Kathon 886 (mixture of methylchloroisothiazolinone and methylisothiazolinone) are used for preservation of cosmetics and metalworking fluids. The lipophilic and cationic biocides PHMB (polyhexamethylene biguanide) and octenidine dihydrochloride are commonly used in hygiene and antiseptic products. The physicochemical properties of these biocides are listed in Table 1.