There is a lot of value to a disinfectant manufacturer of having a sporicidal claim so that the product can be used in healthcare settings to tackle C. difficile spores. However, not all products with a sporicidal claim are in fact sporicidal! Amine-based disinfectants with "sporicidal" claims are being seen increasingly in the marketplace, but these products are unlikely to have meaningful sporicidal activity, as highlighted by a recent letter in the Journal of Hospital Infection.
We posted recently on the questions to ask of products claiming to have sporicidal activity: does the testing match the proposed usage, is the contact time representative of in-use recommendations and practice, has the disinfectant been neutralised effectively in laboratory tests, and was the testing performed in a reputable laboratory? One of the key steps in laboratory disinfectant testing is the neutralisation step. This nullifies the activity of the disinfectant so that an exact contact time can be measured. If this step isn't completed correctly, the disinfectant continues to work beyond the planned contact time, and efficacy can be over-estimated.
One of the main culprits of sporicidal claims that we believe to be misleading are amine-based disinfectants. Prof Jean-Yves Maillard, a world-renowned expert in disinfectant testing, has written a letter in the Journal of Hospital Infection highlighting the challenge of inappropriate neutralisation in laboratory testing resulting in inaccurate "sporicidal" results for these amine-based disinfectants. The lack of a recognised European sporicidal test is a limitation, and so a UK-developed sporicidal testing standard for C. difficile (with an appropriate neutralisation step!) should be considered the gold standard. And no amine-based disinfectants have passed this test. Therefore, we agree with Prof Maillard, that it is puzzling and concerning that products containing solely amines are being used as sporicides in healthcare settings.
A US study has found that Candida auris exhibited a similar level of susceptibility to UV light as Clostridium difficile spores, and was considerably less susceptible than MRSA. These findings suggest that either extended exposure UV cycles or hydrogen peroxide based room disinfection are required to address environmental contamination with Candida auris.
We have posted before on the efficacy of various disinfectants against Candida auris, supporting that chlorine-based disinfectants and chlorhexidine have a role to play in preventing the transmission of Candida species. This latest laboratory study tested the efficacy of a UV room decontamination system against various species of Candida auris and Candida albicans, MRSA, and C. difficile spores. Metal discs with these organisms dried onto them were placed 5 feet from the device at a height of 4 feet with exposure times of 10, 20, or 30 minutes. UV achieved a <2-log reduction on C. auris after 10 minutes of exposure (vs. a >6-log reduction for MRSA), a 4-log reduction after 20 minutes, and a 6-log reduction after 30 minutes. The efficacy profile of UV against C. difficile and C. auris was similar.
This study is in line with the findings of others that C. auris is able to less susceptible to disinfection than other agents. Therefore, extended exposure UV cycles or hydrogen peroxide based room disinfection should be used to tackle environmental contamination with C. auris.