Efficacy of metal ions and isothiazolones in inhibiting Enterobacter cloacae BF-17 biofilm formation

Abstract

Enterobacter cloacae is a nosocomial pathogen. The E. cloacae strain BF-17, with a high capacity for biofilm formation, was screened and identified from industrially contaminated samples, carried out in our laboratory. To develop an efficient strategy to deal with biofilms, we investigated the effects of metal ions, including Na+, K+, Ca2+, Mg2+, Cu2+, and Mn2+, and 3 isothiazolones, on elimination of E. cloacae BF-17 biofilm formation by using a 0.1% crystal violet staining method. The results revealed that higher concentrations of Na+ or K+ significantly inhibited E. cloacae BF-17 biofilm development. Meanwhile, Ca2+ and Mn2+ stimulated biofilm formation at low concentration but exhibited a negative effect at high concentration. Moreover, biofilm formation decreased with increasing concentration of Mg2+ and Cu2+. The isothiazolones Kathon (14%), 1,2-benzisothiazolin-3-one (11%), and 2-methyl-4-isothiazolin-3-one (10%) stimulated initial biofilm formation but not planktonic growth at low concentrations and displayed inhibitory effects on both biofilm formation and planktonic growth at higher concentrations. Unfortunately, the 3 isothiazolones exerted negligible effects on preformed or fully mature biofilms. Our findings suggest that Na+, K+, Mg2+, and isothiazolones could be used to prevent and eliminate E. cloacae BF-17 biofilms.