Keeping it clean with chlorine

Widely used since the 1950’s, with the advantage that bacteria, fungi and viruses do not build up a natural resistance to it - the disinfecting properties of chlorine dioxide could be finding an increasing role at the laboratory bench.

WITH the recent and quite sudden withdrawal from sale of clear soluble phenolics, as a result of the European Biocidal Products Directive, many laboratories have been involved in a rapid search for suitable alternative disinfectants. One such alternative is chlorine dioxide, already well-established in hospitals for instrument decontamination and hard surface disinfection, and now finding an increasing role at the laboratory bench.

The disinfecting properties of chlorine dioxide have been known for over a century. Since the 1950’s it has been widely used for the treatment of drinking water supplies and swimming pools. Now, its applications are widespread. In the food industry for example chlorine dioxide has a role in fruit and vegetable washing, meat and poultry disinfection, and sanitising processing equipment. It is used in cooling systems and towers for legionella control and in personal hygiene products such as mouthwashes, toothpastes and contact lens solutions.

Over the past five years, growing health and safety concerns surrounding the use of glutaraldehyde-based disinfectants for flexible endoscope decontamination have prompted a move away from such chemicals, to be replaced in many cases by chlorine dioxide. While chlorine dioxide is not the only alternative, its safety and efficacy have seen many endoscopy departments switch over to its use for both manual decontamination and for automatic endoscope washer/disinfectors.

The recent introduction of new presentations of chlorine dioxide disinfectants - as wipes, foams, and in burstable sachets that quickly deliver active solution at working concentrations – has considerably extended its medical application and prompted applications in the laboratory for hard surface and equipment disinfection.

Chlorine dioxide is a powerful oxidising agent which causes a bacterial cell to give up electrons, thereby creating a breach through which cell contents pass in an attempt to bring the concentrations on either side of the cell membrane to equilibrium. The cell dies through lysis.
Chlorine dioxide is a broad-spectrum biocide with the advantage that bacteria, fungi and viruses do not build up a natural resistance to it. Environmentally, chlorine dioxide does not form toxic trihalomethanes (THMs) or other chlorinated compounds that are harmful to the environment and which are associated with the use of chlorine, sodium hypochlorite and hypochlorous acid.
The EU Biocidal Products Directive aims to ensure that biocides pose no undue threat to human health or the environment and has already led to the withdrawal of a number of substances. Chlorine dioxide provides a safe, efficacious and cost-effective solution, that is available in a variety of formats to suit the disinfection needs of the laboratory, and is increasingly being written into laboratory disinfection codes of practice.

Box-out. Chlorine dioxide in the laboratory
Of particular interest for the laboratory is the Tristel Duo Foamer, which applies a chlorine dioxide sporicidal foam for decontamination of in vitro diagnostic medical devices, isolators, ventilator cabinets, work surfaces, keyboards, and Tristel Fuse, a liquid solution in a ‘burstable sachet’. This sachet quickly generates 2 litres of chlorine dioxide working solution for decontamination of discard pots, centrifuges, benches, large surfaces, floors and walls.

Tristel Duo kills organisms on a surface with a contact time of just 30 seconds and is effective against a wide range including MRSA, Norovirus, Clostridium difficile, Bacillus subtilis, Mycobacterium tuberculosis and Acinetobacter baumannii. An independent study conducted last year at the School of Life Sciences, Glasgow Caledonian University confirmed its efficacy against two opportunistic pathogens in the hospital environment, epidemic methicillin resistant Staphylococcus aureus (EMRSA) and human Norovirus.

The patented chemistry which forms the basis of Tristel’s range of products rapidly generates chlorine dioxide. Incorporated in the technology is a buffer that stabilises the pH in the range 5.0 to 5.5, and an inhibitor system which protects sensitive materials.

All formulations comprise a base material and an activator, both of which are completely inert and not considered to be COSHH substances, becoming active and biocidal only when mixed.

A surface test methodology was used to evaluate the efficacy of the system against five common strains of EMRSA and the accepted Norovirus surrogate, feline calicivirus. Test data indicated that Tristel Duo effectively reduced each of the five global EMSRA strains by least 5 log10 following the recommended contact time of 30 seconds. For the Norovirus surrogate, infectivity was completely removed to the level of sensitivity of the assay used.

In a published study, P.A. Griffiths, J.R. Babb and A. P. Fraise1 indicated that chlorine dioxide at the test concentration produced a 5 log reduction in one minute under dirty conditions, and the recent HPA Risk Alert2 indicates that chlorine dioxide may be used in laboratories handling mycobacteria.

References
1. Journal of Hospital Infection (1999) 41: 111-121, Mycobactyericidal activity of selected disinfectants using a quantitative suspension test. P.A. Griffiths, J.R. Babb and A. P. Fraise, Hospital Infection Research Laboratory, City Hospital NHS Trust, Dudley Road, Birmingham, B18 7QH.

2. Health Protection Agency Risk Alert 07-001: Replacement of Hycolin with other disinfectants. http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidance/DH_072556

By Paul Swinney. Paul is Chief Executive and one of the founders of Tristel plc, a UK-based company that uses proprietary chlorine dioxide chemistry to create instrument and surface disinfectants. With its origins as a healthcare business specialising in infection control products, Tristel has recently extended its operations to include legionella control in water supplies and contamination control in the food and pharmaceutical industries.

Contact:
Tel: 01638 721500
www.tristel.com