Efficacy of selected biocides in the decontamination of common nosocomial bacterial pathogens in biofilm and planktonic forms

•All biocides were capable of completely killing the bacteria in the planktonic phases.•The biofilms were significantly less susceptible to the biocides than were planktonic cells.•Peracetic acid was relatively the most potent against the bacteria in the biofilms.•Alternative strategy that adopts effective biocides to prevent biofilm growth is needed.

The efficacy and use of biocides to eliminate pathogens in the health care environment are based on their testing against planktonic bacteria. In the environment, bacteria exist in biofilms, as they do on medical devices, and as planktonic or viable non-culturable forms as well. This work aimed to evaluate the efficacy of four biocides against the biofilm and planktonic phases of nine common nosocomial bacteria. The bactericidal activity of the biocides against bacteria in the planktonic form was assessed using a broth microdilution technique. The killing activity of the biocides against biofilms was evaluated using cells grown on polyethylene tubes under a dynamic flow-cell system that was designed for biofilm growth. All biocides completely killed the planktonic bacteria at all concentrations; however, they did not eradicate the biofilms of the same pathogens. Our study highlights the need for an alternative strategy, one that utilizes chemicals that have been tested to disrupt or prevent biofilm growth, in order to enhance current disinfection practice.