'Secondary biofilms' could cause failure of peracetic acid high-level disinfection of endoscopes

The reduced susceptibility of biofilm to disinfectants presents a challenge to the successful reprocessing of medical equipment. This study examined the effect of residual biomass remaining after previous PAA disinfection on tolerance of subsequent mature P. aeruginosa biofilms to PAA. The effect of enzymatic degradation of specific components of P. aeruginosa biofilm EPS on the effectiveness of PAA disinfection was also evaluated.

The presence of residual biomass from previously disinfected biofilms significantly enhanced the tolerance of a subsequent biofilms. A 96hr old “secondary biofilm” formed on disinfected biomass survived PAA concentrations of 4000 ppm, which exceeds the concentrations used in practice for high-level disinfection.

These observations indicate that, under certain circumstances recolonisation of residual EPS can cause failure of disinfection of medical equipment such as endoscopes and emphasises the importance of cleaning of endoscopes prior to disinfection.