Assessment of Chemical Disinfectants Efficacy against Escherichia coli Biofilm Developed on Glass and Wood at Refrigeration and Room Temperatures.

Objectives: The aim of this work was to study the formation of biofilm on glass and wood coupons at refrigeration and room temperatures, different incubation periods and to assess the efficacy of hydrogen peroxide (HP), Para Acetic Acid (PAA), Sodium hypochlorite (SH) and mixture of PAA + SH against the biofilm. Method: 200 μL of 108suspension E. coli ATCC 29922 was inoculated on the coupons inside petri dishes containing 20 ml of tryptic soy broth, incubated at 10 and 270C for 24, 48, 72 and 168 hours. Biofilm developed at each hour above was quantified by bead-vortex followed by agar plating. The action of disinfectants was tested on 168 hours biofilm. The surfaces were exposed to the disinfectants and incubated at 27 °C for 10 minutes, followed by deactivation for 5 minutes. Cells that resisted disinfectants effect were vortexed and enumerated by agar plating. Results: The results showed that E. coli can develop high biofilm on wood apart from glass. After disinfection treatment, HP had the highest efficacy at 27°C followed by PAA then SH, whilst PAA + SH had the least. Conclusion: It can be concluded that HP and PAA can be good disinfectants agents against E. coli biofilm.

Differential biofilm formation and chemical disinfection resistance of Escherichia coli on stainless steel and polystyrene tissue culture plate.

Background: Biofilms are aggregates of microbial cells enclosed in an extracellular polymeric substance and attached to surfaces. Biofilm formation and its resistance to antimicrobials is becoming a serious challenge in food industries and hospital settings. The aim of this work was to study the formation of biofilm by E. coli on Stainless steel (SS) and Polystyrene Tissue Culture Plate (TCP) at 10 and 27°C, and also to assess the action Hydrogen Peroxide (HP), Para Acetic Acid (PAA), Sodium Hypochlorite (SH) and mixture of PAA + SH disinfectants against the biofilm. Methods: 200 μL of 108 suspension of E. coli ATCC 29922 was inoculated on the SS and into the wells of TCP, incubated at 10 and 27°C for 24, 48 72 and 168 hours. Biofilm developed at each incubation hour above was quantified by bead-vortex method followed by agar plating. The action of disinfectants was tested on 168 hours biofilm. The surfaces were exposed to the disinfectants and incubated at 27°C for 10 minutes, followed by deactivation for 5 minutes. Cells that resisted disinfectants action were vortexed and enumerated by agar plating. Results: From the results E. coli developed higher biofilm on SS than TCP at 72 hours and 27°C. After disinfection, HP was the most effective with log reduction value of 1.11 followed by PAA (1.07), then PAA + SH (1.04) while SH was the least (0.92). Conclusions: The result of this work showed that HP and PAA can be good disinfectants against E. coli biofilm.

Evaluation of biofilm formation and chemical sensitivity of Salmonella typhimurium on plastic surface.

S. typhimurium is an important socioeconomic problem in several countries, mainly in developing countries where it is reported as the main responsible for the food-borne disease outbreaks. A biofilm can be explained as a group of cells, diverse species or mono-species that are fixed to a surface and/or to one another. This study aimed to evaluate the biofilm formation of S. typhimurium on the plastic surface as well as to determine the relationship between contact time and incubation temperature. Crystal violet assay was performed to quantify the biofilm formation with and without treatments based on the value of optical density at 600nm of the destaining crystal violet at different interval of time. The outcomes of the result indicated that, the attachment of bacterial cells to the plastic surfaces increased with the increased contact time and determined by temperature. The values of OD600 at 37 °C for 24, 48 and 72 hours were 0.770, 0.968 and 2.363 respectively. This indicated that, the formation of biofilm by S. typhimurium on plastic surfaces varied with contact time. For the disinfectant treatments, hydrogen peroxide with 91 % sensitivity was the highest in treatment of S. typhimurium cells, followed by the mixture of sodium hypochloride and paracetic acid with 70 %, then paracetic acid with 67 %. Considering this result, S. typhimurium formed a biofilm on the plastic surface, hygienic activities on a plastic surface in food industry during handling, processing, distribution and storage of food should be a concerned and these disinfectants are suggested for the treatment of S. typhimurium.