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V. Microbiology of water. A. Waterborne microbial pathogens B. Indicator bacteria for drinking water C. Other indicators for drinking and recreational water. A.W aterborne microbial pathogens Microbiology review:. Microbes in water include: Bacteria Virus Protozoa

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V. Microbiology of water

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V. Microbiology of water

A. Waterborne microbial pathogens

B. Indicator bacteria for drinking water

C. Other indicators for drinking and recreational water


A.Waterborne microbial pathogensMicrobiology review:

  • Microbes in water include:

    • Bacteria

    • Virus

    • Protozoa

  • A few microbes (pathogens) are capable of causing disease, and may be transmitted by water.


Waterborne pathogens:

  • Some common pathogens:

  • Salmonella typhi

  • Escherichia coli

  • Vibrio cholera

  • Pseudomonas aeruginosa

  • Shigella spp.

  • Cryptosporidium

  • Giardia lamblia

  • Norwalkvirus


Cryptosporidum and cryptosporidiosis

Crypto “Oocysts

Cryptosporidium parvum


Giardia lamblia(giardiasis)

Original image by Arturo Gonzalez, CINVESTAV, Mexico. Used with permission of Javier Ambrosio, UNAM, Mexico


Giardia lamblia

  • Giardia lamblia trophozoites live in the small intestine of the host.

  • The trophozoites average about 15 µm in length, have a distinct "tear-drop" shape and two nuclei at the anterior end

Giardia lamblia troph.  The two nuclei are easy to see in this image.  (Original image from a Japanese language site tentatively titled "Internet Atlas of Human Parasitology."


B. Indicator bacteria for Drinking Water:

  • Indicator microorganisms are used to indicate an increased risk of pathogen contamination due to fecal contamination.

  • Indicator microbes should be:

    • Always present when feces/sewage is present

    • Always absent when feces/sewage is absent

    • Survives longer in water than any of the pathogenic species

    • Easily isolated and identified.


Indicator bacteria:

  • Coliform bacteria (E. coli-like) are the most often used indicator bacteria for water quality assessment in the U.S.


Characteristics of coliforms:

  • Aerobic or facultative,

  • Gram-negative,

  • Non-spore forming,

  • Bacilli,

  • which ferment lactose to form acid and/or gas within 48 hours at 35 oC.


More specific coliforms:

  • Coliforms are often found naturally in soil, water, plants, etc.

  • Fecal coliforms are a more specific coliforms that usually come from feces.

  • E. coli is the most specific indicator


Guidelines and methods for enumerating coliforms:

  • EPA guidelines for coliforms in drinking water are < 1 CFU/100 ml.

  • Tests used to isolate and enumerate coliforms in water include:

    • m-Endo media

    • m-FC media

    • MUG media


C. Other indicators for drinking and recreational water

  • Limitation of Total coliform as drinking water microbial indicator

    • Ubiquitous.

    • Less resistant to traditional disinfection.

    • Proliferate in the biofilms of water distribution systems


  • Limitation of Fecal coliforms

    • Klebsiella pneumoniae

    • Less resistant to traditional disinfection.

  • Limitation of E. coli

    • Less resistant to traditional disinfection.


Microbial Indicators for Recreational Water

  • Total coliform?

  • Fecal coliform?

    • Average 200 MPN/100 ml

  • E. Coli (fresh water)?

    • Average 126 MPN/100 ml.

  • Enterococci (salt water)

    • Average 35 MPN/100 ml.


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