'Secondary biofilms' could cause failure of peracetic acid high-level disinfection of endoscopes
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Published on: December 9, 2022
A B Akinbobola1, N J Amaeze2, W G Mackay2
1Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria.
Introduction:
The reduced susceptibility of biofilms to disinfectants presents a challenge to the successful reprocessing of medical equipment. This study examined the effect of residual biomass remaining after previous disinfection with peracetic acid (PAA) on the tolerance of subsequent mature Pseudomonas aeruginosa biofilms to PAA. The effect of enzymatic degradation of specific components of the extracellular polymeric substance (EPS) of P. aeruginosa biofilm on the effectiveness of PAA disinfection was also evaluated.
Methods:
The susceptibility of biofilm grown on the biomass of PAA-killed biofilm to PAA was compared with the PAA susceptibility of biofilm grown in wells of a 24-well plate by evaluating their viability using the plate count assay. The effect of PAA on biofilm biomass was measured using crystal violet quantification of total biofilm biomass, while its effect on the polysaccharide and protein components of biofilm EPS was quantified using the phenol-sulphuric acid assay or Bradford assay, respectively. A confocal microscope was used to visualize the distribution of living and dead cells in biofilms grown on residual biofilm biomass.
Findings:
The presence of residual biomass from previously disinfected biofilms significantly enhanced the tolerance of subsequent biofilms. A 96-h-old 'secondary biofilm' formed on disinfected biomass survived PAA concentrations of 4000 ppm, which exceeds the concentrations used in practice for high-level disinfection.
Conclusion:
These observations indicate that, under certain circumstances, recolonization of residual EPS can cause failure of disinfection of medical equipment such as endoscopes, and emphasizes the importance of cleaning endoscopes prior to disinfection.
Insights
Residual biomass from disinfected biofilms significantly increases tolerance to peracetic acid (PAA), a disinfectant. This finding highlights the critical need for thorough cleaning of medical equipment before disinfection to prevent biofilm regrowth and ensure patient safety.
Area of Science:
- Microbiology
- Biomedical Engineering
- Infectious Diseases
Background:
- Biofilms exhibit reduced susceptibility to disinfectants, complicating medical equipment reprocessing.
- Peracetic acid (PAA) is a common disinfectant, but its efficacy against biofilms requires further investigation.
- Residual biomass from previous disinfection can impact the effectiveness of subsequent disinfection protocols.
Purpose of the Study:
- To investigate the impact of residual biomass on the tolerance of Pseudomonas aeruginosa biofilms to PAA.
- To assess the role of extracellular polymeric substance (EPS) components in biofilm tolerance.
- To evaluate the effectiveness of PAA disinfection in the presence of residual biofilm material.
Main Methods:
- Comparing PAA susceptibility of biofilms grown on residual biomass versus standard plates using plate count assays.
- Quantifying total biofilm biomass, polysaccharides, and proteins using crystal violet, phenol-sulphuric acid, and Bradford assays.
- Visualizing cell viability within biofilms using confocal microscopy.
Main Results:
- Residual biomass from disinfected biofilms significantly enhanced the tolerance of subsequent biofilms to PAA.
- Mature biofilms grown on residual biomass survived PAA concentrations exceeding 4000 ppm.
- Enzymatic degradation of EPS components was evaluated for its effect on PAA efficacy.
Conclusions:
- Recolonization of residual EPS can lead to disinfection failure in medical equipment like endoscopes.
- Thorough cleaning of medical equipment prior to disinfection is crucial.
- Understanding residual biomass effects is vital for effective infection control in healthcare settings.
