Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-17T19:54:16.062Z Has data issue: false hasContentIssue false
  • English
  • Français

Most probable numbers of organisms: revised tables for the multiple tube method

Published online by Cambridge University Press:  19 October 2009

Hilary E. Tillett
Hilary E. Tillett
Affiliation:
Public Health Laboratory Service, Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ
Rights & Permissions [Opens in a new window]

Summary

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Estimation of numbers of organisms is often made using dilution series, for example when examining water samples for coliform organisms. In this paper the most probable numbers (MPNs) are calculated for a 15-tube series consisting of five replicates at three consecutive tenfold dilutions. Exact conditional probabilities are computed to replace previous approximations.

When growth is observed in several of the tubes it is not realistic to select a single MPN. Instead a most probable range (MPR) should be reported. But using an MPR creates problems when comparison has to be made with a legislated, single-valued Standard. It is suggested that the wording of the Standards should be expressed differently when the multiple tube method is used.

Type
Research Article
Information
Epidemiology & Infection , Volume 99 , Issue 2 , October 1987 , pp. 471 - 476
Copyright
Copyright © Cambridge University Press 1987

References

REFERENCES

American Public Health Association, American Water Works Association, Water Pollution Control Federation (1985). Standard Methods for the Examination of Water and Wastewater. 16th edition. Washington DC: APHA.Google Scholar
Department of the Environment, Department of Health and Social Security, Public Health Laboratory Service (1983). The Bacteriological Examination of Drinking Water Supplies. London: HMSO.Google Scholar
Gray, R. D. & Lowe, G. H. (1976). The preparation of simulated water samples for the purpose of bacteriological quality control. Journal of Hygiene 76, 49–56.CrossRefGoogle ScholarPubMed
McCrady, M. H. (1918). Tables for rapid interpretation of fermentation-tube results. Public Health Journal, Toronto 9, 201–220.Google Scholar
Tillett, H. E. (1986). Reporting bacteriological counts from water samples. Proceedings of International Workshop on Statistical Aspects of Water Quality, Burlington, Canada, 1985 (ed. El-Shaarawi, & Kwiatkowski, ). Amsterdam: Elsevier Scientific.Google Scholar
Tillett, H. E. & Coleman, R. (1985). Estimated numbers of bacteria in samples from non-homogeneous bodies of water: how should MPN and membrane filtration results bo reported ? Journal of Applied Bacteriology 59, 381–388.CrossRefGoogle Scholar