Indicator organism

Indicator organisms are used as a proxy to monitor conditions in a particular environment, ecosystem, area, habitat, or consumer product. Certain bacteria, fungi and helminth eggs are being used for various purposes.

Types

Indicator bacteria

Main article: indicator bacteria

The presence of coliform bacteria, such as E. coli, in surface water is a common indicator of faecal contamination. Coliform bacteria in water samples may be quantified using filter-based methods or the most probable number (MPN) method, a probabilistic test which assumes cultivable bacteria meet certain growth and biochemical criteria. If preliminary tests suggest that coliform bacteria are present at numbers in excess of an established cut-off (the Coliform Index), faecal contamination is suspected and confirmatory assays such as the Eijkman test are conducted.

Coliform bacteria selected as indicators of faecal contamination must not persist in the environment for long periods of time following efflux from the intestine, and their presence must be closely correlated with contamination by other faecal organisms. Indicator organisms need not be pathogenic.[1]

Non-coliform bacteria, such as Streptococcus bovis and certain clostridia may also be used as an index of faecal contamination.[2]

Indicator fungi

Penicillium species, Aspergillus niger and Candida albicans are used in the pharmaceutical industry for microbial limit testing, bioburden assessment, method validation, antimicrobial challenge tests, and quality control testing.[3] When used in this capacity, Penicillium and A. niger are compendial mold indicator organisms.[3]

Molds such as Trichoderma, Exophiala, Stachybotrys, Aspergillus fumigatus, Aspergillus versicolor, Phialophora, Fusarium, Ulocladium and certain yeasts are used as indicators of indoor air quality.[4][5][6]

Indicator helminth eggs

Identification and quantification of helminth eggs at UNAM university in Mexico City, Mexico

Helminth eggs (or ova) are a good indicator organism to assess the safety of sanitation and wastewater reuse systems for resource recovery because they are the most environmentally resistant pathogens of all pathogens (viruses, bacteria, protozoa and helminths) and can in extreme cases survive for several years in soil.[7]

See also

References

  1. ↑ "Fecal Coliform as an Indicator Organism" (PDF). Wastewater treatment environmental fact sheet. New Hampshire Department of Environmental Services. 2003. Retrieved 2007-11-30.
  2. ↑ Gerardi, Michael H.; Mel C. Zimmerman (January 2005). Michael H. Gerardi, ed. Wastewater Pathogens. Wastewater Microbiology Series. Hoboken, NJ: John Wiley & Sons, Inc. p. 147. ISBN 978-0-471-20692-7.
  3. 1 2 Clontz, Lucia (2009). "Microorganisms of interest". Microbial Limit and Bioburden Tests: Validation Approaches and Global Requirements,Second Edition (2nd ed.). Boca Raton, FL: CRC Press. pp. 31–33. ISBN 9781420053494.
  4. ↑ Jantunen, Matti; Jaakkola, Jouni J. K.; Krzyzanowski, M., eds. (1997). "20: Bacteria and fungi". Assessment of Exposure to Indoor Air Pollutants, WHO Regional Publications European Series, No. 78. Copenhagen: WHO Regional Office Europe. pp. 101–102. ISBN 9289013427.
  5. ↑ Cole, Eugene C.; Dulaney, Pamela D.; Leese, Keith E.; Hall, Richard M.; Foarde, Karin K.; Franke, Deborah L.; Myers, Frank M.; Berry, Michael A. (1996). "Biopollutant Sampling and Analysis of Indoor Surface Dusts: Characterization of Potential Sources and Sinks". In Tichenor, Bruce A. Characterizing Sources of Indoor Air Pollution and Related Sink Effects, Volume 1287. West Conshohocken, PA: ASTM International. pp. 164–164. ISBN 9780803120303.
  6. ↑ Heikkinen, M.S.A.; Hjelmroos-Koski, M.K.; Haggblom, M.M.; Macher, J.M. (2004). "Chapter 13: Bioaerosols". In Ruzer, L.S.; Harley, N.H. Aerosols Handbook: Measurement, Dosimetry, and Health Effects. Boca Raton, FL: CRC Press. pp. 377–378. ISBN 9780203493182.
  7. ↑ WHO (2006). Guidelines for the Safe Use of Wastewater, Excreta and Greywater, Volume 4 Excreta and Greywater Use in Agriculture. (third ed.). Geneva: World Health Organization. ISBN 9241546859.

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