Enterobacteriaceae & the Food Plant Environment - continued

Environmental microbiological monitoring can be used to indicate unacceptable conditions or practices and thereby aid in controlling pathogenic bacteria such as Listeria and Salmonella species. The frequency of sampling and number of samples is dictated by past performance and product risk. The first goal of the environmental monitoring program is to establish acceptable microbiological criteria for each sample site. This is done by sampling test sites when the plant environment is in an acceptable condition. Once microbiological criteria are established, each sample site is regularly monitored for compliance with the criterion. When testing shows a site to be unacceptable, prompt action must be taken to find the source of contamination and to sanitize the area. It is important that each sampling site be sampled using the same sampling technique and test methods. This ensures that test results can be compared to previous test results.

Enterobacteriaceae as Indicator Organisms
The choice of which organism(s) to test for in the environment is important. Testing for pathogens (e.g., Listeria monocytogenes and Salmonella sp.) is both costly and time consuming. It is preferable to test for suitable indicator organisms. In my opinion, the species that comprise Enterobacteriaceae make excellent indicator organisms for assessing post-process sanitation.

Although, coliform organisms have long served as indicator bacteria, there is no logical reason to limit testing only to coliform species. All species in the family Enterobacteriaceae are potentially of interest, particularly some of the lactose negative species. Organisms belonging to the family

Enterobacteriaceae are heat-sensitive and chemical sanitizer-sensitive bacteria and therefore should be controlled in the plant environment. Members of the Enterobacteriaceae family commonly colonize both wet and dry factory environments and are excellent indicators of equipment contamination from environmental sources.

Detecting Enterobacteriaceae with Petrifilm Plates
The 3M Petrifilm plate is a very cost effective and rapid method for detecting Enterobacteriaceae in the environment. Sampling should be done with a swab or a sponge moistened with a suitable buffer. The swab or sponge is then rinsed in the buffer and the buffer is plated onto the Petrifilm
Enterobacteriaceae plate. Results are available within 24 hours. Post-process food contact surfaces should be free of Enterobacteriaceae contamination. Non-food contact surfaces may have varying numbers of Enterobacteriaceae depending on the site sampled and the nature of food manufacturing processes in the plant. Generally, dry plant environments should have less than 10³ Enterobacteriaceae per 100cm². However, each plant should determine the  microbiological criteria that best meet the needs of its processes. When environmental microbiological monitoring is combined with proper raw materials and process controls, there is no need or value in finished product testing.

Source: 3M MicroMessenger, Volume IV 1995