Browsing by Author "Rayner, Joanna"

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Biofilm penetration and disinfection efficacy of alkaline hypochlorite and chlorosulfamates
(2001-09) Stewart, Philip S.; Rayner, Joanna; Roe, Frank L.; Ree, Wayne M.
AIMS: The purpose of this study was to compare the efficacy, in terms of bacterial biofilm penetration and killing, of alkaline hypochlorite (pH 11) and chlorosulfamate (pH 5.5) formulations. METHODS AND RESULTS: Two-species biofilms of Pseudomonas aeruginosa and Klebsiella pneumoniae were grown by flowing a dilute medium over inclined stainless steel slides for 6 d. Microelectrode technology was used to measure concentration profiles of active chlorine species within the biofilms in response to treatment at a concentration of 1000 mg total chlorine l-1. Chlorosulfamate formulations penetrated biofilms faster than did hypochlorite. The mean penetration time into sim 1 mm-thick biofilms for chlorosulfamate (6 min) was only one-eighth as long as the penetration time for the same concentration of hypochlorite (48 min). Chloride ion penetrated biofilms rapidly (5 min) with an effective diffusion coefficient in the biofilm that was close to the value for chloride in water. Biofilm bacteria were highly resistant to killing by both antimicrobial agents. Biofilms challenged with 1000 mg l-1 alkaline hypochlorite or chlorosulfamate for 1 h experienced 0.85 and 1.3 log reductions in viable cell numbers, respectively. Similar treatment reduced viable numbers of planktonic bacteria to non-detectable levels (log reduction greater than 6) within 60 s. Aged planktonic and resuspended laboratory biofilm bacteria were just as susceptible to hypochlorite as fresh planktonic cells. CONCLUSION: Chlorosulfamate transport into biofilm was not retarded whereas hypochlorite transport was clearly retarded. Superior penetration by chlorosulfamate was hypothesized to be due to its lower capacity for reaction with constituents of the biofilm. Poor biofilm killing, despite direct measurement of effective physical penetration of the antimicrobial agent into the biofilm, demonstrates that bacteria in the biofilm are protected by some mechanism other than simple physical shielding by the biofilm matrix. SIGNIFICANCE AND IMPACT OF THE STUDY: This study lends support to the theory that the penetration of antimicrobial agents into microbial biofilms is controlled by the reactivity of the antimicrobial agent with biofilm components. The finding that chlorine-based biocides can penetrate, but fail to kill, bacteria in biofilms should motivate the search for other mechanisms of protection from killing by antimicrobial agents in biofilms.
Effect of catalase on hydrogen peroxide penetration into pseudomonas aeruginosa biofilms
(2000-02) Stewart, Philip S.; Roe, Frank L.; Rayner, Joanna; Elkins, James G.; Lewandowski, Zbigniew; Ochsner, Urs A.; Hassett, Daniel J.
The penetration of hydrogen peroxide into biofilms formed by wild-type and catalase-deficient Pseudomonas aeruginosa strains was measured using microelectrodes. A flowing stream of hydrogen peroxide (50 mM, 1 h) was unable to penetrate or kill wild-type biofilms but did penetrate and partially kill biofilms formed by an isogenic strain in which the katA gene was knocked out. Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm.
Establishment of experimental biofilms using the modified robbins device and flow cells
(1999) Hall-Stoodley, Luanne; Rayner, Joanna; Stoodley, Paul; Lappin-Scott, H. M.
Recent studies have shown that biofilms (a complex organization of bacterial cells present at a surface or interface, which produces a slime-like matrix) represent the principal form of bacterial growth in all environments studied to date (1). There are numerous advantages to bacteria growing in biofilms. These include extended protection against environmental changes, antimicrobial agents such as chemical disinfectants and antibiotics (2) and grazing predators such as amebae (3), as well as providing increased access to limited nutrients (4). Biofilms are of interest in medical, industrial, and natural environments for several reasons. For example, they can act as reservoirs from which the dissemination of pathogens may occur. Legionella pneumophila has been shown to be harbored within biofilms formed within drinking water pipelines (5). Similarly, it is well established that biofilms can colonize numerous types of medical implants (6). In industrial systems, detrimental effects may occur following biofilm growth such as reductions in heat-transfer efficiency and flow capacity. Biofouling may also markedly increase corrosion (7). Finally, biofilms represent a bacterial architecture that may support genetic transfer, nutrient utilization, and biodegradation (8).
Experimental biofilms and their applications in the study of environmental processes
(1999) Rayner, Joanna; Lappin-Scott, H. M.
Prevalence of microbial biofilms on selected fresh produce and household surfaces
(2004-08) Rayner, Joanna; Veeh, Richard Harold; Flood, Janice Elizabeth Desi
Investigations of biofilms in domestic environments are sparsely represented in the literature. In this study, samples of various household surfaces, including food, laundry and kitchen items, were analyzed for evidence of biofilm presence. Visualization of the surfaces was carried out using cryostage scanning electron microscopy (CSEM) and light microscopy. Qualitative evidence of the presence of biofilm formation was obtained from all of the sample groups analyzed, suggesting the widespread existence of microorganisms in biofilms on domestic surfaces. This suggests that biofilms may be important in household hygiene, and highlights the need for standardized, approved biofilm methods suitable for consumer products testing.