Neutralising duff "sporicidal" claims of amine-based disinfectants

Clostridium difficile (C. diff) infection is linked to significant morbidity and mortality and represents a leading cause of healthcare associated infection (HCAI)¹. When C. diff is expelled from the body, the living form survives for only a short time before it transforms into an endospore to protect itself from the environment allowing it to survive for many months². Bacterial endospores are generally considered to be the toughest challenge for disinfectants. Consequently, they are used as the ‘gold standard’ for disinfectant testing; if it can kill bacterial endospores, you make the assumption that it can kill everything else besides. To eliminate C. diff from surfaces, a disinfectant with proven sporicidal activity (ability to kill spores not just inhibit their growth) should be used.

There is a lot of value to a disinfectant manufacturer in having a sporicidal claim so that the product can be used in healthcare settings to tackle C. diff spores. However, recently we have begun to see that not all products with “sporicidal” claims are in fact sporicidal. For example, amine-based disinfectants e.g. quaternary ammonium compound (QAC) and triamine-based products are among the list. It has been well known for over 25 years that QACs do not exhibit sporicidal activity^3,4.

Professor Jean-Yves Maillard, a world-renowned expert in disinfectant testing, highlights the challenge of inappropriate neutralisation in laboratory testing resulting in inaccurate “sporicidal” results for these amine-based disinfectants⁵. To claim sporicidal activity, the disinfectant must destroy 10³ spores under specific conditions⁶. Even with these we are still seeing sporicidal claims for compounds known not to be sporicidal — there is no European test for C. diff. In testing, once the required contact time is reached the disinfectant is neutralised to stop any further activity — so that it mimics real life conditions. Sometimes completely neutralising the compound is difficult, particularly the amine-based disinfectants, because they are made up of several chemicals. If this step isn’t completed correctly, the disinfectant continues to work beyond the planned contact time and efficacy can be over-estimated. The lack of a recognised European sporicidal test is a limitation, and so a UK-developed sporicidal testing standard for C. diff (requiring a 10⁵ reduction in spores and an appropriate neutralisation step) should be considered the gold standard. No amine-based disinfectants have passed this test.

Due to the lack of sporicidal efficacy of amine-based disinfectants, an oxidising agent with proven efficacy should be used. Peracetic acid is an oxidising agent with a broad spectrum of microbicidal activity at low concentrations and is effective at reducing incidence of C. diff infection. Clinell Sporicidal Wipes combine peracetic acid with hydrogen peroxide providing two distinct sporicidal mechanisms by which the wipe acts⁷, they have shown to reduce C. difficile associated disease by 72%⁸.

When decontamination of the surface environment is suboptimal it can place staff, patients and visitors at risk⁹. GAMA Healthcare agrees with Professor Maillard, that it is both puzzling and concerning that products containing solely amines are being used as sporicides in healthcare settings.

References

1. Weber DJ, Anderson DJ, Sexton DJ, Rutala WA. Role of the environment in the transmission of Clostridium difficile in health care facilities. Am J Infect Control. 2013; 41(5 Suppl): S105-10.
2. Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect Dis. 2006;6:130.
3. Russell AD. Bacterial spores and chemical sporicidal agents. Clin Microbiol Rev. 1990; 3(2):99-119.
4. Wesgate R, Rauwel G, Criquelion J, Maillard JY. Impact of standard test protocols on sporicidal efficacy. J Hosp Infect. 2016; 93(3): 256-62.
5. Maillard J-Y. Are amine only-containing products sporicidal? J Hosp Infect. 2018, doi: 10.1016/j.jhin.2018.02.002.
6. BS EN14885:2015. Chemical disinfectants and antiseptics. 2015. British Standard Institution: London.
7. Leggett MJ, Spencer Schwarz J, Burke PA, McDonnell G, Denyer SP, Maillard JY. Mechanism of Sporicidal Activity for the Synergistic Combination of Peracetic Acid and Hydrogen Peroxide. Appl Environ Microbiol. 2016; 82(4):1035-1039.
8. Carter Y, Barry D. Tackling C difficile with environmental cleaning. Nursing Times. 2011; 107(36): 22-25.
9. Shaughnessy MK, Micielli RL, DePestel DD, Ardnt J, Strachan CL, Welch KB, Chenoweth CE. Evaluation of hospital room assignment and acquisition of Clostridium difficile infection.Infect Control Hosp Epidemiol. 2011; 32(3):201-206.