V. Microbiology of waterV. Microbiology of waterA. Waterborne microbial pathogensA. Waterborne microbial pathogens

B. Indicator bacteria for drinking waterB. Indicator bacteria for drinking waterC. Other indicators for drinking and C. Other indicators for drinking and

recreational waterrecreational water

A.WA.Waterborne microbial pathogensaterborne microbial pathogens Microbiology review:Microbiology review:

Microbes in water Microbes in water include:include:– BacteriaBacteria– Virus Virus – ProtozoaProtozoa

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

Waterborne pathogens:Waterborne pathogens:

Some common pathogens:Some common pathogens:

Salmonella typhiSalmonella typhi Escherichia coli Escherichia coli Vibrio choleraVibrio cholera Pseudomonas aeruginosa Pseudomonas aeruginosa ShigellaShigella spp. spp. CryptosporidiumCryptosporidium Giardia lambliaGiardia lamblia NorwalkvirusNorwalkvirus

Cryptosporidum and cryptosporidiosis

Cryptosporidium parvum Crypto “Oocysts

Giardia lamblia(giardiasis)

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

Giardia lamblia Giardia lambliaGiardia lamblia

trophozoites live in the trophozoites live in the small intestine of the small intestine of the host.host.

The trophozoites The trophozoites average about 15 µm in average about 15 µm in length, have a distinct length, have a distinct "tear-drop" shape and "tear-drop" shape and two nuclei at the anterior two nuclei at the anterior end 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 B. Indicator bacteria for Drinking Water:Drinking Water:

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

Indicator microbes should be:Indicator microbes should be:– Always present when feces/sewage is presentAlways present when feces/sewage is present– Always absent when feces/sewage is absentAlways absent when feces/sewage is absent– Survives longer in water than any of the Survives longer in water than any of the

pathogenic speciespathogenic species– Easily isolated and identified.Easily isolated and identified.

Indicator bacteria:Indicator bacteria: ColiformColiform bacteria ( bacteria (E. coliE. coli-like) are the -like) are the

most often used indicator bacteria for most often used indicator bacteria for water quality assessment in the U.S.water quality assessment in the U.S.

Characteristics of coliforms:Characteristics of coliforms: Aerobic or facultative,Aerobic or facultative, Gram-negative,Gram-negative, Non-spore forming,Non-spore forming, Bacilli, Bacilli,

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

More specific coliforms:More specific coliforms: Coliforms are often found naturally Coliforms are often found naturally

in soil, water, plants, etc.in soil, water, plants, etc.

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

E. coli E. coli is the most is the most specific indicatorspecific indicator

Guidelines and methods for Guidelines and methods for enumerating coliforms:enumerating coliforms:

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

Tests used to isolate and Tests used to isolate and enumerate coliforms in water enumerate coliforms in water include:include:– m-Endo media m-Endo media – m-FC media m-FC media – MUG mediaMUG media

C. Other indicators for drinking and C. Other indicators for drinking and recreational waterrecreational water

Limitation of Limitation of Total coliformTotal coliform as as drinking water microbial drinking water microbial indicatorindicator– Ubiquitous.Ubiquitous.– Less resistant to traditional Less resistant to traditional

disinfection.disinfection.– Proliferate in the biofilms of Proliferate in the biofilms of

water distribution systemswater distribution systems

Limitation of Limitation of Fecal coliformsFecal coliforms – Klebsiella pneumoniaeKlebsiella pneumoniae – Less resistant to traditional disinfection.Less resistant to traditional disinfection.

Limitation of Limitation of E. coliE. coli – Less resistant to traditional disinfection.Less resistant to traditional disinfection.

Microbial Indicators for Microbial Indicators for Recreational WaterRecreational Water

Total coliform?Total coliform? Fecal coliform?Fecal coliform?

– Average 200 MPN/100 mlAverage 200 MPN/100 ml E. Coli (fresh water)?E. Coli (fresh water)?

– Average 126 MPN/100 ml.Average 126 MPN/100 ml. Enterococci (salt Enterococci (salt

water)water)– Average 35 MPN/100 ml.Average 35 MPN/100 ml.