Inactivation of biofilm bacteria

Abstract

The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2°C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of bioflim bacteria to monochloramine disinfection ranged from 2to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria.

Biology and Diseases of Rats

“…Pseudomonas aeruginosa is one of a group of organisms that forms biofilms, layers of bacteria, usually with reduced metabolic activity, embedded in a dense glycocalyx. Bacteria in a biofilm are extraordinarily resistant to chlorine (150-3000 times more resistant than free-floating bacteria) and monochloramine (2-to 100-fold) (LeChevallier et al, 1988) and may be inaccessible to antibiotics. Nonetheless, chlorination (10-13 ppm) or acidification (pH 2.5-3.0) can significantly reduce the colonization of mice with P. aeruginosa but will not eliminate infection.…”

Antimicrobial activity and effectiveness of a combination of sodium hypochlorite and hydrogen peroxide in killing and removingPseudomonas aeruginosabiofilms from surfaces

“…EPS are hydrated polyanionic polysaccharide matrices produced by polymerases, some of which are affixed to the lipopolysaccharide components of the cell walls (Chimielewski and Frank 2003;Jass et al 2003). EPS not only provide protection to biofilm inhabitants by preventing access of biocides and sequestering toxins, acquiring nutrients and reducing desiccation but also by inducing phenotypic variation and intercellular communication (Heinzel 1998;Lechevallier et al 1988;Cochran et al 2000;Wirtanen et al 2001;Chimielewski and Frank 2003;Jass et al 2003). Biofilms are highly complex microbial communities that occur in both natural and artificial environments.…”

Bacterial biofilm on contact lenses and lens storage cases in wearers with microbial keratitis

“…Bacteria in natural environments are almost exclusively found in adherent microcolonies, and possess characteristics and properties which are unique to, and reflect, their particular niche (Costerton et al 1987). Adherent cells within such a biofilm are significantly more resistant to antimicrobial agents compared with planktonic organisms (LeChevalier et al 1988;Anwar et al 1990). This resistance has been attributed to the physical exclusion of antimicrobial agents by the polysaccharide bulk of the biofilm.…”