Fact sheet on Enterobacteria

General
Enterobacteriaceae (Enterobacteria) play an important role in food microbiology. Many members of this large family are highly relevant in foods as hygiene indicators, spoilage organisms or pathogens. Because many bacterial genera belong to this family, their properties are very diverse.

• More specific information on some representatives: see fact sheets on Coliform bacteria, Salmonella, Escherichia coli, STEC / VTEC / EHEC and Yersinia enterocolitica.

Characteristics

• Rod-shaped bacteria
• Gram-negative
• Oxidase-negative
• Catalase-positive

Origin / Occurrence

• Widespread in our environment (e.g., soil, plants and surface water)
• For some genera (e.g., Escherichia coli and Salmonella) the intestine of animals and humans is the natural reservoir

Significance

• Hygiene indicators (e.g., Escherichia coli)
• Spoilage organisms (e.g., Serratia spp.)
• Pathogens (e.g., Salmonella)
• Part of the normal microbial plant flora (e.g., Pantoea spp.)

Important
Enterobacteriaceae occur in many foods. The interpretation of test results depends on the food, the number of enterobacteria and possibly the bacterial genus or strains. When present in elevated numbers, enterobacteria are often an indicator of hygiene deficiencies, errors in production/storage or potential spoilage. Certain members, such as Salmonella, can cause disease.
In plant-based foods (e.g., leafy salads, sprouts, cereals, seeds …) Enterobacteriaceae are not a suitable indicator for hygiene failures or spoilage because some members of this family are part of the normal microbial plant flora.

Growth conditions

• Temperature:
  • Optimum: generally between +30 °C and +37 °C
  • Minimum: mostly +7 °C (depending on the species, exceptions even down to 0 °C)
  • Generally no growth above +50 °C
• pH: growth at pH 5.5 to 9.0 (depending on the species, exceptions even down to pH 4.4)
• a_w value: growth at high water activity of at least 0.95
• Oxygen requirement: growth with and without oxygen (facultatively anaerobic)

Inactivation by heating

• At +72 °C for at least 2 minutes exposure time vegetative bacteria are killed (Note: monitor core temperature)

1. Check the implementation of cleaning and disinfection:
   1. Hygiene plan
   2. Implementation of cleaning and disinfection e.g., dosing of disinfectant, contact time, use of suitable and clean materials and cleaning cloths
2. Avoid moisture residues and biofilms. Ensure good drying of equipment, devices and surfaces
3. Train employees on potential errors and corrective measures
4. Repeat cleaning and disinfection
5. Verify effectiveness by visual on-site checks, environmental testing and follow-up testing

1. Review work organization in the facility
   1. Separate work areas, equipment and utensils for raw and processed foods
   2. Separation of "clean" and "unclean" areas and activities
2. Train employees on potential errors and improvements
3. Verify effectiveness by visual on-site checks and follow-up testing

1. Train employees on potential errors and corrective measures
2. Regular cleaning and disinfection of hands or regular glove changes
3. Regular changing of work clothing. Ensure cleanliness of work clothing
4. Train employees regarding infection control requirements
5. Verify effectiveness by visual on-site checks and follow-up testing

1. Request traceability of the cold chain during transport and from the supplier
2. Check incoming and storage temperatures
3. Monitor cooling temperatures and the cold chain during processing, transport and sale
4. If over-ageing (or exceeded shelf life) is suspected, carry out appropriate storage tests
5. Verify effectiveness by follow-up testing

1. Check products at goods receipt for e.g., incoming/transport temperature, shelf life, packaging, deviations or abnormalities
2. This also applies to goods before use in production. In case of doubt do not use the food and ask a supervisor
3. Check microbiological specifications. Possibly initiate laboratory testing of suspicious products or request results from the supplier
4. Verify effectiveness by follow-up testing

1. Check processes, production protocols and documentation
2. Inactivation of most bacteria from a core temperature of +72 °C for at least 2 minutes. Exceptions are, for example, heat-stable spores and toxins. In these cases much higher temperatures and exposure times are required. Further information can be found in the respective information sheets (fact sheets)
3. Check correctness of processes and temperatures
   1. In general, holding temperatures above +60 °C are required
   2. Rapid cooling: after 3 hours a core temperature of at least +7 °C must be reached (special caution is required for large quantities)
4. Verify effectiveness by follow-up testing

1. Check processes, environmental conditions, production protocols and documentation
2. Verify effectiveness by follow-up testing