Sanosil disinfectants Effect on biofilms

Transcription

1 Sanosil disinfectants Effect on biofilms Sanosil Norge AS, Brannfjellveien 86 A, 1181 Oslo Tlf.: E-post: sanosil.no Des 007 Effect on Biofilms/en SANOSIL 1/8

2 What are biofilms? Biofilms consist of a mixture of bacteria, fungi, protozoa and/or algae, living in symbiosis with and from each. They are generally perceived as a layer of slime or a coating of varying thickness, colour and consistency, and frequently form on gaseous and liquid phase boundary layers, such as pipes, cooling towers, drains and other water transportation systems. The characteristic biofilm slime matrix consists of extracellular polymeric substance (EPS) produced by the microorganisms, forming a hydrogel with water. Biofilms and environmental resistance EPS consists of various long-chain polysaccharides, such as alginates and celluloses, which can form a remarkably stable matrix. The food industry makes use of these characteristics for products such as thickening agents. For microorganisms, living in a biofilm offers a range of advantages. They have a more consistent food supply, have a degree of protection from desiccation, and enjoy considerable protection from biocides and other adverse environmental influences. Resistance to chlorine, ozone and UV radiation in particular increases substantially with increasing biofilm thickness. Combating biofilms with chlorine dioxide ClO 2 The general consensus in the literature is that the best agent against biofilms is chlorine dioxide (ClO 2 ). It has been repeatedly demonstrated that 70 day treatment cycles with 0.2 mg/l the maximum permitted dose for drinking water treatment results in a significant reduction in microorganisms (but does not destroy all microorganisms, cf. Otte et al., 2004; Lenz, 2011). The corrosiveness of ClO 2 can often be a problem however (Hubbard et al., 2009). In addition, for many facilities, setting up, operating and maintaining an expensive ClO 2 system is simply not financially viable. In such cases, operators aim to achieve a similar result through the use of a range of chemicals and biocides. Biofilm resistance to hydrogen peroxide and/or silver Since both hydrogen peroxide and silver have been used with some success for water disinfection and preservation, it seems logical to consider their use against biofilms. The idea is basically sound, but there is an important problem hydrogen peroxide alone (especially in its native, unstabilised state) is broken down by catalase produced by the biofilm. The rate at which this occurs varies. Shock disinfection, for example, is only considered to be reliably effective at concentrations of 10,000 ppm or more for several hours. By contrast, silver, especially if used alone, has difficulty penetrating the biofilm matrix and often precipitates on the surface of the biofilm. This makes it hard for silver to exert its strong oligodynamic effect and to bring its bacteriostatic/preservative properties to bear. Des 007 Effect on Biofilms/en SANOSIL 2/8

3 Using hydrogen peroxide and silver in combination against biofilms Various attempts have been made to exploit the synergies generated by using hydrogen peroxide and silver together in a single system. About 30 years ago, Sanosil AG became the first company anywhere in the world to achieve this breakthrough and to produce in its labs, a product which combined the oxidising effect of hydrogen peroxide with the outstanding preservative effect of silver. This product was Sanosil Super 25. Effect of stabilised hydrogen peroxide on biofilms Standard hydrogen peroxide products tend to break down very rapidly on contact with biofilms. This can severely limit their efficacy. To achieve maximum effect, the hydrogen peroxide needs, as in Sanosil disinfectants, to be highly stabilised. This inhibits decomposition of the hydrogen peroxide for a period following initial contact with the surface of the biofilm and enables the peroxide to penetrate the biofilm structure. The action of the catalase produced by the biofilm then leads to the release of oxygen from the peroxide. In addition to their oxidising effect, the fine bubbles produced exert a physical, mechanical effect. The expansion of the bubbles within the biofilm matrix literally blows/tears the matrix apart. The resulting biofilm fragments detach from the structure, leaving holes, which in turn allow further peroxide to penetrate into the structure. Under optimal conditions, the entire biofilm coating is rapidly detached from the substrate and broken up. 1. Stabilised hydrogen peroxide (blue) comes into contact with the biofilm structure (brown) 2. Thanks to their stability, the peroxide molecules are able to penetrate the film structure 3. The peroxide which has penetrated the film begins to release oxygen 4. The oxygen bubbles come together, expand and blow the biofilm apart. Des 007 Effect on Biofilms/en SANOSIL 3/8

4 Biofilm in a test tube with Sanosil disinfectant. The lacerating effect of the oxygen bubbles is clearly visible. Des 007 Effect on Biofilms/en SANOSIL 4/8

5 Biofilm in a Petri dish Wetted with a few drops of 1000 ppm Sanosil solution. There is a noticeable difference between wetted and unwetted areas. Des 007 Effect on Biofilms/en SANOSIL 5/8

6 Biofilm in a PVC tube Shock disinfection with 1000 ppm Sanosil After disinfection Des 007 Effect on Biofilms/en SANOSIL 6/8

7 Effect of Sanosil disinfectants on microorganisms Once the biofilm structure has been broken up, the individual microorganisms are virtually defenceless against the dual-phase effect of the disinfectant. Whilst the cell walls are broken open by oxidation, silver blocks the microorganisms ability to reproduce and obtain energy. This results in excellent elimination rates and long-term efficacy. Des 007 Effect on Biofilms/en SANOSIL 7/8

8 Our instructions for use are based on comprehensive experiments. The advice we give is based on the best current knowledge. Since usage and storage conditions are beyond our control, it does not, however, claim to be definitive. Product descriptions and information on the properties of the preparations do not contain any statement on liability for damages. Sanosil Norge AS, Brannfjellveien 86 A, 1181 Oslo Tlf.: E-post: sanosil.no Des 007 Effect on Biofilms/en SANOSIL 8/8