Fact sheet on coliform bacteria

General
Coliform bacteria are a group of bacteria within the family Enterobacteriaceae. They play an important role in food microbiology as hygiene indicators. Some members can cause severe foodborne gastrointestinal illnesses, but in routine diagnostics they are not regarded as primary pathogens.

Characteristics

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

Origin / Occurrence

• Widespread in our environment (e.g., soil, plants and surface water)
• Coliform bacteria are also natural intestinal inhabitants of animals and humans

Significance

• Hygiene indicators
• Can also indicate fecal contamination (e.g., Escherichia coli)

Important

Among coliform bacteria there may also be agents that can be facultatively pathogenic for vulnerable groups. These include, for example, Klebsiella, Enterobacter, Citrobacter and E. coli.
Coliform organisms occur in many foods. The interpretation of test results depends on the food and the number of coliform bacteria. When present in elevated numbers, coliform bacteria are often an indicator of hygiene deficiencies, errors in production/storage or potential spoilage.
In plant-based foods (e.g., leafy salads, sprouts, cereals, seeds …) coliform bacteria are not a suitable indicator for hygiene failures or spoilage, since some members are part of the normal microbial flora of plants. This also applies to some raw animal-origin foods, e.g., in raw milk cheese.

Growth conditions

• Temperature:
  • Optimum: generally at +30 °C to +37 °C
  • Minimum: usually around +7 °C (depending on the species, exceptions even down to 0 °C)
  • Generally no growth above +50 °C
• pH value: 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, minimum approx. 0.95
• Oxygen requirement: growth with and without oxygen (facultatively anaerobic)

Inactivation by heating

• Vegetative bacteria are inactivated at +72 °C for a minimum of 2 minutes contact time (Note: check core temperature)

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

1. Review workplace 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 staff on potential errors and corrective measures
3. Verify effectiveness by visual on-site inspections and follow-up testing

1. Train staff on potential errors and corrective measures
2. Regular hand cleaning and disinfection and regular changing of gloves
3. Regular changing of work clothing. Ensure cleanliness of work clothing
4. Train employees on infection control requirements
5. Verify effectiveness by visual on-site inspections and follow-up testing

1. Request traceability of the cold chain from the transporter or supplier
2. Check incoming and storage temperatures
3. Monitor cooling temperatures and cold chain during processing, transport and sale
4. If overage (i.e., excessive shelf life) is suspected, perform appropriate storage tests
5. Verify effectiveness by follow-up testing

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

1. Check processes, production records and documentation
2. Inactivation of most bacteria occurs at a core temperature of +72 °C for at least 2 minutes. Exceptions include heat-stable spores and toxins; in these cases substantially higher temperatures and/or longer exposure times are required. Further information can be found in the respective information sheets (fact sheets)
3. Verify the correctness of processes and temperatures
   1. In general, hot-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 records and documentation
2. Verify effectiveness by follow-up testing