Microorganisms - Enterobacteria

Food Safety Testing – Enterobacteriaceae

Enterobacteriaceae is a large family of Gram-negative bacteria recognized as an important group in the food industry for monitoring hygiene and sanitation. This group includes a full array of microorganisms, including all coliform bacteria. Its members run the gamut from bacteria like Salmonella and E. coli, well-known to cause foodborne illness, to food spoilage agents to various microorganisms normally present in the human intestinal tract as part of the gut flora. Their ubiquitous distribution makes it nearly inevitable some members of Enterobacteriaceae will enter the food chain.

Enterobacteriaceae are characterized as rod-shaped, oxidase-negative, facultative anaerobes which ferment glucose to acid and/or carbon dioxide gas. Generally motile, they tend to be 1–5 µm in length.

Non-pathogenic Enterobacteriaceae are considered “indicator organisms” in the food industry as their detection and enumeration (using selective media such as the Neogen® Petrifilm® Enterobacteriaceae Count Plates) can indicate improper processing and poor sanitation in the processing environment.

Quality assurance professionals have found that testing for a group of organisms rather than one specific genus or species provides a bigger target for detection. Additionally, Enterobacteriaceae are good indicators when monitoring environmental conditions and overall hygiene in a facility because they are readily inactivated by sanitizers, but when sanitation is inadequate, they can colonize a variety of niches in the processing plant.

Regulations, Scientific Methods

Different countries have different guidelines and regulations with varying acceptance levels for non-pathogenic Enterobacteriaceae, so food manufacturers have followed different criteria and sampling plans based on their location.

When it comes to hazard control steps, Enterobacteriaceae are heat-sensitive, so pasteurization or cooking is most often performed to prevent biological hazards like Salmonella in finished product. (Enterobacteriaceae are also susceptible, like most Gram-negative bacteria, to damage from extreme cold, but because some cells have demonstrated an ability to survive long periods of freezing, this method is not a reliable control measure or lethality step.)

After these steps are taken, product samples are extracted and tested for Enterobacteriaceae to verify that the heat treatment is working. Presence of Enterobacteriaceae in milk after pasteurization, for example, may indicate inadequate pasteurization or post-processing contamination. The outcome of testing for Enterobacteriaceae is added assurance that the manufacturing process is under control.