Real-world testing of the durability claims of a commercially available spray-on surface biocide

Self-disinfecting biocidal surfaces have been proposed as a solution to prevent infections caused by the transmission of microorganisms from frequently touched surfaces in hospitals and other settings. For example, surface anchoring quaternary ammonium salt (SAQAS)-based biocides are purported to maintain their antimicrobial potency for up to 30 days and are available as spray-on formulations. We tested the 30-day potency claim of a commercially available spray-on SAQAS-based biocide (“SAQAS-A”) under “real-world” conditions in a microbiology laboratory where regular cleaning is routine. To do this, we determined the background microbial burden on high-traffic floor areas, routinely used bench areas, frequently touched handles, and glass surfaces for 30 days before and after applying SAQAS-A. Experiments were repeated three times, and data was analysed using two Generalised Linear Mixed Models. We observed that for >80% of bench samples, the number of viable bacteria recovered was below the highest acceptable level of 2.5 CFU/cm ² , with minimal reduction in CFU recovery observed after SAQAS-A treatment. In contrast, the number of floor and glass samples in which the microbial burden exceeded 2.5 CFU/cm ² was greater after biocide application (12.7 and 73%, respectively) than before (4.8 and 37%, respectively). Analysis of all data using two statistical models confirmed that the application of SAQAS-A had no antimicrobial effect. In conclusion, our results indicate that SAQAS-A was ineffective in preventing surface contamination over 30 days in a real-world scenario where routine cleaning occurs.