Klebsiella

(endorsed 1996)

Guideline

Coliforms detected in a water supply may include Klebsiella spp.

General description

Klebsiella spp. are inherently environmental organisms that survive and sometimes multiply in suitable waters. They are associated with roots of plants and can grow to high levels on the leaves of vegetables. They are frequently present in raw waters, and can increase to high levels in waters containing pulp mill wastes.

They are also found in the faeces of a significant proportion of healthy people.

K. pneumoniae and K. oxytoca are significant opportunistic pathogens in hospitals, but the relationship between infections and drinking water is at best dubious, given the wide distribution of members of this genus in the environment.

The genus is heterogenous and has been difficult to classify. Four species are now included: K. pneumoniae, K. oxytoca, K. planticola, and K. terrigena. A fifth species, K. mobilis, has been proposed, but it remains controversial whether this should be classified in this genus or that of Enterobacter (Grimont et al. 1991).

As the organisms have similar sensitivity to disinfection to E. coli and some bacterial enteric pathogens, their presence in drinking water indicates that disinfection has been inadequate.

Australian significance

Klebsiella spp. have been detected in Australian drinking water, but there is no evidence that they have caused disease.

Method of detection and identification

Klebsiella spp. are Gram-negative nonsporing oxidase-negative rod-shaped bacteria, capable of aerobic and facultatively anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are able to ferment lactose, with the production of acid and gas within 48 hours at 35–37°C.

Most Klebsiella spp. can be quantified in water by either multiple tube dilution, or membrane filtration methods (AS1095.4.1), which are followed by suitable tests for identification of the genus.

Health considerations

Klebsiella may colonise patients in hospital, being spread mainly by the frequent handling which occurs in intensive care units. Those most at risk are people with impaired defence mechanisms, such as the elderly or the very young, people with burns or excessive wounding, those undergoing immunosuppressive therapy, or those with acquired immune deficiency syndrome (AIDS). From colonisation, invasive infections may occur. On rare occasions Klebsiella may cause infections, including destructive pneumonia, in apparently healthy people. These problems appear to be associated with K. pneumoniae and K. oxytoca.

Derivation of guideline

No guideline value is established, if used for operational monitoring, numbers should be established on a system specific basis, taking into consideration relevant historical data and an understanding of the characteristics of the system. Klebsiella spp. form a significant proportion of the organisms identified as coliforms in standard tests for indicator bacteria, and these organisms are thus covered by the guideline for coliforms.

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NOTE: Important general information is contained in PART II, Chapter 5

References

AS1095.4.1 (1981). Microbiological examination of water for dairy purposes. Microbiological methods for the dairy industry. Australian Standard, Standards Association of Australia, Sydney, NSW.

Grimont F, Grimont PAD and Richard C (1991). The genus Klebsiella. In: Balows A, Truper HG, Dworkin.

M, Harder W and Schleifer KH, The prokaryotes. Springer-Verlag Publishers, 2nd edition, New York, United States, pp 1217–1224 and 1249–1261.