Characterizing bacterial resistance to preservatives and disinfectants

Bacterial resistance to preservatives and disinfectants is a problem with serious economic and health consequences. Understanding the basis of resistance may lead to strategies or chemistries capable of reversing or subverting the mechanism. A collection of bacterial isolates resistant to dimethoxydimethyl hydantoin, glutaraldehyde, methylchloroisothiazolone/methylisothiazolone, and benzisothiazolone, as well as combination preservatives, has been gathered. In addition, a perusal of the literature also reveals reports of resistance to quaternary ammonium compounds, biguanides, iodophors, and peroxides, suggesting no particular chemistry is immune to resistance development. The majority of isolates in the collection are members of the genera Pseudomonas and Burkholderia, along with several representatives of the genus Alcaligenes and Enterobacter. Characterization of their susceptibility to other preservatives and disinfectants revealed several patterns of cross-resistance. All isolates were resistant to biocides other than the selecting compound. Several isolates were cross-resistant to either a quaternary ammonium compound or hydrogen peroxide; one P. fluorescens isolate was cross-resistant to both disinfectants. The presence of cross-resistance among preservatives and disinfectants has serious implications for the ability to eradicate resistant microbes from contaminated surfaces or manufacturing processes using commonly accepted disinfectants.