Fact sheet on Pseudomonas aeruginosa in drinking water

General information
Pseudomonads belong to the family Pseudomonaceae. Of particular importance for drinking water hygiene is Pseudomonas aeruginosa, which is a common cause of so-called hospital infections (nosocomial pathogen). Pseudomonas aeruginosa is an undemanding microorganism that can multiply even with low nutrient availability.
The Drinking Water Ordinance requires the absence of Pseudomonas aeruginosa (0 CFU/100 ml). If a positive result for Pseudomonas aeruginosa occurs, appropriate countermeasures must be initiated immediately. A positive finding of Pseudomonas aeruginosa in a drinking water sample according to the Drinking Water Ordinance must be reported to the competent authority.

Characteristics

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

Source / Occurrence

• Widely distributed in our environment (e.g. soil, water, plants and animals).
• Survives for a long time in stagnant water
• Often found after construction work and in newly installed piping systems

Significance

• In water hygiene, Pseudomonas aeruginosa plays a particularly important role as an indicator organism. It indicates contamination and biofilms in drinking water.
• In medical facilities and hospitals, Pseudomonas aeruginosa is a particularly feared pathogen, e.g. causing wound and urinary tract infections (a cause of hospital-acquired infections).

Growth conditions

• Temperature:
  • Optimum: +25 °C to +37 °C
  • Minimum: +5 °C
  • Generally no growth above +50 °C
• pH value: growth at pH 5.0 to 8.0.
• a_w-value: multiplication at a water activity of at least 0.95.
• Oxygen requirement: obligate aerobic

Inactivation by heating

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

1. If an aerator (Perlator) is present: remove and disinfect. Replace depending on condition
2. Remove contamination and/or biofilms
3. If possible, flame-sterilize the final section of the water outlet after cleaning
4. Verify success by follow-up testing

1. Perform staged investigations if necessary to better identify the location of contamination in the piping network
2. Engage a specialist company or building services to investigate the cause
3. Carry out disinfection
4. Verify success by follow-up testing

1. Thorough visual inspection of the treatment system
2. Check maintenance intervals, replace filters if necessary
3. Engage a specialist company or building services for inspection/maintenance
4. Verify success by follow-up testing

For drinking water from private water supply systems, i.e. from private wells and springs

Contamination due to interventions/repairs in the spring intake/well chamber

Contamination after heavy rainfall (contamination by surface water)

Contamination due to construction defects in the spring intake/well chamber (leakage, age-related wear)

1. Thorough visual inspection of the spring intake/well chamber and surroundings
2. Regular checks of the private water supply system, especially after possible weather-related influences (heavy rain, prolonged drought)
3. Carry out the inspections required by the health authority at regular intervals
4. Engage a specialist company at appropriate intervals for cleaning and disinfection of the spring intake/well chamber
5. Verify success by follow-up testing

For flake ice, crushed ice and ice cubes
Hygiene deficiencies:

in the machine including utensils
or

in the connection hose (supply water)
or

in the distribution system (domestic installation)

1. Thorough visual inspection of machines and connection hoses. This usually also requires disassembling parts of the machines
2. Remove contamination or biofilms
3. Thorough cleaning and disinfection of machines and components (possibly by a specialist company)
4. Thorough cleaning and disinfection of utensils (e.g. scoop)
5. Replace the connection hose between machine and distribution system at regular intervals
6. Replace contaminated or damaged hoses (e.g. brittle, porous) immediately
7. Test the drinking water from the distribution system (before the inlet to the machine)
8. Verify success by follow-up testing

Plumbed-in water dispensers (connected to the distribution system)
Hygiene deficiencies:

in the dispenser
or

in the connection hose (supply water)
or

in the distribution system (domestic installation)

1. Thorough visual inspection of the water dispenser including the connection hose
2. Remove contamination or biofilms
3. Thorough cleaning and disinfection of the water dispenser (usually by a specialist company)
4. Possibly replace the connection hose between machine and distribution system at regular intervals
5. Replace contaminated or damaged hoses (e.g. brittle, porous) immediately
6. Test the drinking water from the distribution system (before the inlet to the dispenser)
7. Verify success by follow-up testing