Microbial control in domestic kitchens and laboratory biofilms
Document Type Article
It has been documented that a substantial number of food poisoning outbreaks originate from the domestic kitchen environment. Therefore, to ascertain public awareness of domestic hygiene, 335 participants were questioned on issues relating to their perceptions of risks associated with the kitchen environment, cleaning regimes and disinfection knowledge. The results revealed an unsatisfactory understanding of food safety awareness and practices. These findings were substantiated by a high level of microorganisms frequently enumerated from a number of household kitchen surfaces, as determined by a swabbing campaign in 35 homes.
To demonstrate the impact environmental parameters can have on disinfectant activity, efficacy tests were carried out on Escherichia coli and Salmonella enterica subsp. enterica serovar Typhimurium when in suspension, surface attached or when proliferated into a biofilm on stainless steel or glass in the presence of a range of soil materials. Viability was determined by image analysis of cells stained with acridine orange. Results showed that surface attachment enhanced resistance over their free cell counterparts, but biofilm cells exhibited greatest resistance. Presence of soiling material also greatly reduced the antimicrobial activity.
Methodology can have an impact on viability results. To study this aspect three fluorochromes (acridine orange, BacLight Live/Dead Viability Kit and 5-cyano-2,3-di-4-tolyl-tetrazolium chloride (CTC) combined with Syto 9) were used in conjunction with fluorescent microscopy and image analysis to determine the antimicrobial activity of disinfectants. Similar results were generally recorded for the first two dyes however the use of the CTC system gave lower microbial reduction. To determine just how rapidly resistance in a bioflm can develop, a flowcell was set up and bacterial susceptibility monitored over time and upon the release of the biofilm. It was found that not only did resistance increase with time, but that it was retained by the cells upon release.