Spray-on Surface Biocide Shown to be Ineffective

A new study showed that a commercial spray that claims to make surfaces self-disinfecting had no antimicrobial effect shortly after application.

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, the researchers said. 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.

The researchers 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, researchers 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.

Researchers observed that for greater than 80% of bench samples, the number of viable bacteria recovered was below the highest acceptable level of 2.5 colony-forming units (CFU)/cm², with minimal reduction in CFU recovery observed after SAQAS-A treatment. On the other hand, the number of floor and glass samples in which the microbial burden exceeded 2.5 CFU/cm² was greater after biocide application (12.7% and 73%, respectively) than before (4.8% and 37%, respectively).

In turn, analysis of all data using two statistical models confirmed that the application of SAQAS-A had no antimicrobial effect either after five or 30 days of application. 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.