Implementing a Disinfection Action Plan
There are several important areas to be addressed in an effective disinfection action plan.
Threat Assessment
Assessing the level of bacterial contamination includes observing odor and appearance of contact surfaces as well as plate culture to determine presence of pathogens.
Physical Cleaning
After the initial assessment, cleaning is the next step and must be thoroughly performed before applying the disinfectant. Experts agree that cleaning alone can remove over 90% of bacteria from surfaces, significantly enhancing the efficacy of the disinfectant compound and minimizing the chances of regrowth/colonization.
This initial cleaning step involves scrubbing, brushing and scraping to physically remove as much gross dirt, biofilm, debris and organic material as possible from all contact surfaces. Cleaning is also important since many disinfectants may be inactivated or ineffective in the presence of organic debris or waste. Disposal of debris into dumpsters should only occur if there is no zoonotic risk of disease transmission. All personnel should wear appropriate protective clothing and footwear. If a zoonotic disease is suspected, enhanced personal protective equipment should be used according to NIOSH protocol.
Surfactant Wash
Washing or sanitizing further reduces the number of microorganisms in the area to a safer level. Educt a anionic or non-ionic surfactant into the treatment equipment, allow sufficient contact time and then rinse vigorously to remove organic and other material. Although cleaning may appear to remove all debris, microscopic biofilm may remain on surfaces and interfere with disinfection efficacy. Biofilm is a complex aggregation of bacteria adhering to surfaces in an exopolysaccharide matrix, resulting in a thin residue that could remain after cleaning. These bacteria are highly resistant to disinfection. Surfactant detergents, mechanical scrubbing, brushing and scraping during cleaning help reduce biofilm. Adding phosphoric acid to the surfactant mixture can be quite efficacious in reducing biofilm accumulation. Multiple bed volumes of fresh water should be rinsed through the system to ensure complete removal of surfactants and contaminants. Some disinfectants can be inactivated by soaps and detergents.
Disinfection
Selection of the proper disinfectant will depend on the microorganism suspected, as well as environmental factors and safety issues. Always read the entire product label and follow dilution instructions explicitly to ensure that the safest, most effective concentration is applied.
To achieve effective disinfection, surfaces must be thoroughly wet and clean; properly mixed disinfectant should be applied at a rate of 0.1 – 0.4L/minute or according to manufacturer’s specifications. Dilution ratios of disinfectant will vary according to type of disinfectant and the specific application. Disinfectant should remain for the appropriate contact time, which will vary with the product and particular application. Equipment should be thoroughly rinsed before returning the system to service.
Evaluation
To verify that all pathogens have been destroyed or reduced to acceptable levels, a follow-up evaluation of the equipment should be conducted. While visual inspection of cleanliness is important, bacteriological samples should be obtained to determine the true effectiveness of the cleaning and disinfection protocol. Failure of a disinfection program usually results from the selection of an ineffective disinfectant, careless use of an effective disinfectant, or environmental factors, such as water hardness, heavy metals, pH, additional contaminants, and water temperature. The timing of sample collection is important. The best time to sample is 2-3 days after disinfection. Surface samples for small, smooth areas, can be collected by wiping or swabbing a sterile swab across a non-porous surface. Commercially available methods include RODAC™ and Petrifilm™ Plates (3M).
These small, flat, sample-ready plates allow on-site microbial testing and are commonly used for food processors. These plates are available for a variety of specific microorganisms or classes (aerobic count plates, coliform count, environmental Listeria etc…) as well as yeast and mold counts and can also be used direct contact or swab applications. Other methods of environmental sampling include surface samples collected by Ultrafilter membrane. Each step of the disinfection action plan (assessment, cleaning, washing/sanitizing, disinfection) should be evaluated for problems encountered and usefulness or efficiency of the cleaning or disinfection techniques.
References and Further Reading
U.S. Environmental Protection Agency. Pesticides: Regulating Pesticides – Registering Pesticides. www.epa.gov/cgi-bin/epaprintonly.cgi
U.S. Environmental Protection Agency. Disinfectants for use on hard surfaces – Efficacy data requirements. www.epa.gov/oppad001/dis_tss_docs/dis-01.htm
U.S. Environmental Protection Agency. Read the Label first
www.epa.gov/pesticides/kids/hometour/label/read
National Institute for Occupational Safety and Health. Comprehensive Procedures for collecting environmental samples for culturing Bacillus anthracis.
http://www.cdc.gov/niosh/unp¬envsamp.html
Antec International Ltd. Emergency disease control: The critical need for modern formulated disinfectants. http://www.antecint.co.uk/main/basichem.htm
Health Canada. Environmental Sampling for the detection of microorganisms.
www.hc-sc.gc.ca/food¬ailment/mh-dm/mhe-dme/compendium/volume_3/e_mflp41
Grow AG. Writing guidelines to require disinfection. Rev. sci. tech. Off. int. Epiz. 1995:14(2);469-477.
http://www.cfsph.iastate.edu
Tamasi G. Testing disinfectants for efficacy. Rev. sci. tech. Off. int. Epiz. 1995:14(1):75-9.
Joklik WK (editor). Ch. 10. Sterilization and disinfection. Zinsser Microbiology. 1992. Appleton and Lange, Connecticut. pp. 188-200.
Kennedy J, Bek J, Griffin D. Selection and use of disinfectants. University of Nebraska Cooperative Extension G00-1410-A. November 2000.
Maris P. Modes of action of disinfectants. Rev. sci. tech. Off. int. Epiz. 1995:14(1):47-55.
Jeffrey DJ. Chemicals used as disinfectants: Active ingredients and enhancing additives. Rev. sci. tech. Off. int. Epiz. 1995:14(1):57-74.
Envirocheck® Rodac plates for surface testing
http://service.merck.de/microbiology/tedisdata/prods/4976¬1_07084_0001.html
3M Petrifilm Plates. Environmental Monitoring Procedures. http://multimedia.mmm.com/mws/mediawebserver.dyn?nnnnnnX7fzBnHRon0RonnnLjxZiqY1Un-