Pseudomonas aeruginosa

(endorsed 1996)

Guideline

No guideline value has been established for Pseudomonas aeruginosa in drinking water.

General description

Pseudomonas aeruginosa is commonly found in faeces, soil, water and sewage. It cannot be used as an indicator of faecal contamination, as it is not universally present in faeces and sewage, and it may also multiply in an enriched aquatic environment and on the surface of suitable organic materials in contact with water. Its presence, however, can be used to assess the general cleanliness of water distribution systems and the quality of bottled waters.

P. aeruginosa has also been found in various foods.

Australian significance

Though P. aeruginosa occurs in Australian drinking water supplies, it has only been associated with cases of folliculitis (inflammation of the hair follicles) in health-spa whirlpools.

Treatment of drinking water

Free available chlorine residuals of 0.2–0.5 mg/L are generally sufficient to control P. aeruginosa in water.

Method of identification and detection

P. aeruginosa is a member of the family Pseudomonadaceae and is a polarly-flagellated, Gram-negative rod. When grown in suitable media it is capable of producing pigments, the most significant of which are the nonfluorescent phenazine pigments, pyocyanin and fluorescin. Pigment may not be produced by strains of P. aeruginosa recovered from clinical specimens and the ability to produce pigment may be lost on subculture. Like other fluorescent pseudomonads in natural waters, P. aeruginosa strains produce catalase and oxidase, produce ammonia from arginine, use citrate as the sole source of carbon, and areaerobic.

P. aeruginosa can grow at 41–42°C (AS 1095.4.1.13 1981). The blue-green pigment produced differs from the fluorescent pale green pigment (fluorescin) produced by other species of fluorescent pseudomonads found in water. The organism can also grow anaerobically in stab cultures of nitrate agar.

Health considerations

P. aeruginosa is a classical opportunistic pathogen. It rarely becomes established in, and even more rarely infects, the intact host but colonises damaged systems, for example burn wounds, the respiratory tract of people with underlying disease, physically damaged eyes etc. From these it may invade the body, causing destructive lesions or septicaemia. Immunosuppressed people, particularly those with low polymorph counts, are at risk. Contaminated ‘irrigation’ fluids or pharmaceutical agents (e.g. eye drops) delivered to damaged areas have caused severe infection.

While it is clearly undesirable for water supplies to hospitals to have high counts of this organism (or other opportunistic pathogens), a direct association of hospital infections with drinking water sources is yet to be established. High counts of this organism in spa and swimming pool water have been linked with rashes and superficial infections of the outer ear canal (Calderon and Mood 1982, Jones and Bartlett 1985).

Derivation of guideline

Owing to the widespread occurrence of the organism and its opportunistic pathogenicity, it is difficult to set a guideline for drinking water. However, the presence of the organism in drinking water may indicate a serious deterioration in bacteriological quality, often accompanied by taste, odour and turbidity complaints associated with low rates of flow and increased water temperatures.

References

AS 1095.4.1.13, (1981). Examination of water for Pseudomonas aeruginosa by membrane filtration. Australian Standard, Microbiological methods for the dairy industry. Standards Association of Australia, Sydney, NSW.

Calderon R and Mood EW (1982). An epidemiological assessment of water quality and ‘swimmer’s ear’. Archives of Environmental Health, 73, 300–305.

Jones F and Bartlett CLR (1985). Infections associated with whirlpools and spas. Journal of Applied Microbiology (symposium supplement, microbial aspects of water management), 61s–66s.