The efficacy of physical and chemical disinfection is affected by a number of parameters which can be attributed to the product formulation or process and their delivery system, their application in practice, but also to the type of microorganisms. Among microorganisms, bacterial endospores such as Clostridioides difficile spores are the least susceptible to chemical disinfection, whilst pigmented moulds remain a challenge for UVC radiation processes. Enveloped viruses (SARS-CoV2) or multidrug resistant bacteria are not necessarily a problem, but their persistent on surfaces can be. Microbial persistence on surfaces can be linked to biofilms, complex multi species microbial communities on surfaces embedded in an extracellular polymeric matrix. Biofilms enable microbial survival on surfaces over long duration despite regular surface cleaning and disinfection. Newly discovered environmental dry surface biofilms (DSB) which are commonly found on hospital environmental surfaces [1] are particularly of a concern for “traditional’ liquid surface disinfection since physical/mechanical removal together with the biocidal formulation are necessary to eradicate DSB [2]. An important challenge is to demonstrate the efficacy of product or process. The use of standard efficacy tests, when available for a specific technology, does not necessarily reflect product efficacy in practice. In Europe, virucidal testing in suspension is barely adequate to demonstrate efficacy for surface application. Testing for the microbicidal efficacy of new approaches combining a bundle of interventions or based on novel technology, such as those based on photocatalysis, can be difficult and relies on in situ testing, which has its own limitation, or ad hoc protocols that may not translate to product claim. Overall, the aim of surface disinfection is to render a surface “safe”, a very loose term, which until now relied on demonstrating a decrease in microbial viability. The additional requirement for some product efficacy test to investigate microbial transfer post-treatment provides additional evidence of product/process efficacy. Testing for residual efficacy or product is still in its infancy but may prove important to render surface safe post application.

Examples are used to show where the market for disinfection is heading. How new regulatory requirements are influencing the market environment and how scientific findings are calling proven products into question and opening up opportunities for innovation. And what effects, but also excesses, the pandemic has led to.

This talk introduces the mobile disinfection robot “DeKonBot 2”. It can drive autonomously around public buildings. Using its sensors and advanced image processing software, it detects potentially contaminated surfaces such as door handles, light switches or elevator buttons. With its robotic arm and the attached cleaning brushes, it removes coarse dirt and comprehensively applies the disinfection fluid. Images: With its camera and a newly developed 3D sensor the robot detects and localize the objects to be cleaned (left). It then starts the cleaning process (right).

In pharmaceutical industry or in health care facilities, where proper hygiene strategies are crucial to maintain high standards of safety and to ensure wellbeing of the end consumers, the control of bacterial spores is still challenging due to the lack of fast-acting and material-friendly sporicidal disinfectants [1]. Sporosan is a peroxynitrous acid-based broad-spectrum disinfectant that inactivates bacterial spores, viruses and bacteria within a couple of seconds. Because of its material-friendly formulation it can be used for spore inactivation on medical devices, surfaces and even on hands. Sporosan’s active substance peroxynitrous acid (ONOOH) is a highly reactive molecule with a short lifetime of approx. 0.9 s [2]. Its uncharged, small, and linear chemical structure enables it to penetrate the cell membrane of pathogenic agents and trigger oxidative stress inside [3]. Because the lifetime of ONOOH is so short, the molecule itself cannot be stored easily. Consequently, it must be continuously generated in a disinfection process. This continuous generation is achieved by a reaction of hydrogen peroxide and nitrite as liquid precursors. The two liquids are kept separate until application and are mixed only shortly before use. Depending on the design of the starting materials and the use of active retarders, the disinfecting effect on the surface lasts for 10 to 300 seconds. Studies in accredited test laboratories (Dr. Brill Hamburg, Labor Enders Stuttgart, Hygiene Nord Greifswald) show the effectiveness of Sporosan against bacteria, persistent spores, and resistant viruses within 30-60 seconds. In addition, complete inactivation of Clostridioides difficile spores on medical devices was achieved within 6 seconds. In this presentation, a brief introduction into the chemical production process of ONOOH is given together with an insight of the achieved microbiological results. Finally, an overview of the various application areas of Sporosan is given.