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

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.

Influence of delivery system on the efficacy of low concentrations of hydrogen peroxide in the disinfection of common healthcare-associated infection pathogens.

INTRODUCTION: The ability of healthcare-associated infection pathogens to survive on environmental surfaces is well known. Disinfection is employed to reduce or remove these pathogens but disinfection failures still occur. One method with the potential to improve disinfection efficacy is whole-room disinfection with hydrogen peroxide (H2O2). AIM: To determine the influence of delivery system on the efficacy of low-concentration H2O2 on common healthcare-associated infection pathogens. METHODS: SanoStatic (electrostatic spray) was compared with SanoFog (fogging) in terms of performance for delivery of 5% H2O2 and trace silver ions for disinfection. The bacterial test challenges were vancomycin-resistant Enterobacterales (VRE), extended-spectrum ß-lactamase (ESBL)-producing Klebsiella pneumoniae (ESBLK), carbapenemase-producing Enterobacterales (CPE), meticillin-resistant Staphylococcus aureus (MRSA), Clostridium difficile spores, Bacillus atropheus and Geobacillus stearothermophilus commercial spore strips. FINDINGS: SanoFog and SanoStatic were effective when tested under the conditions of experimentation reported here. For VRE, ESBLK, CPE and MRSA, SanoFog and SanoStatic were comparable in performance. For C. difficile we concluded the following: SanoFog was most effective for disinfection of C. difficile spores when compared to SanoStatic. CONCLUSION: Whereas SanoFog and SanoStatic were effective against bacterial cells, the current practice of using SanoFog and SanoStatic together would be effective for disinfection of C. difficile spores based on investigations under the conditions of experimentation reported here. The spore strips results were not comparable to the results either for the vegetation cells (VRE, ESBLK, CPE, and MRSA) or for C. difficile spores.

Effect of different fruit components, aeration and cold storage at 5°C on the germination of ascospores of Neosartorya fischeri.

UNLABELLED: Germination is the process by which a spore is transformed from a dormant state of metabolic activity to one of high activity. Effects of different fruit components, aeration and cold storage at 5°C on the germination of ascospores of Neosartorya fischeri after heat treatment were investigated by measuring rate and percentage germination and outgrowth of fungal biomass. Some activated spores reverted back to dormancy after 12 and 24 h of storage at 5°C. Ascospores germinated easily in acetate buffers. Germination of ascospores was retarded in medium containing citric acid and sugars. Ascospores cultured under low aeration showed no signs of germination. Different food components and growth conditions have varying effects on germination of ascospores. SIGNIFICANCE AND IMPACT OF THE STUDY: The findings of this study can be used in the fruit industry to predict the effect of some fruit components on the germination of heat-resistant ascospores. The impact of cold storage on ascospores, which may be activated by heat schedules used to manufacture some types of fruit products, will help in determining the best storage conditions for enhanced shelf life to be adopted immediately after heat treatment. These findings also help to determine for how long a fruit juice is safe at room temperature after production before mycotoxin synthesis by heat-resistant fungi sets in.