V. Microbiology of water V. Microbiology of water A. Waterborne microbial pathogens B. Indicator bacteria for drinking water C. Other indicators for drinking.

Présentation au sujet: "V. Microbiology of water V. Microbiology of water A. Waterborne microbial pathogens B. Indicator bacteria for drinking water C. Other indicators for drinking."— Transcription de la présentation:

1 V. Microbiology of water V. Microbiology of water A. Waterborne microbial pathogens B. Indicator bacteria for drinking water C. Other indicators for drinking and recreational water

2 A.Waterborne microbial pathogens Microbiology review: u Microbes in water include: –Bacteria –Virus –Protozoa u A few microbes (pathogens) are capable of causing disease, and may be transmitted by water.

3 Waterborne pathogens: u Some common pathogens: u Salmonella typhi u Escherichia coli u Vibrio cholera u Pseudomonas aeruginosa u Shigella spp. u Cryptosporidium u Giardia lamblia u Norwalkvirus

4 Cryptosporidum and cryptosporidiosis Cryptosporidium parvum Crypto “Oocysts

5 Giardia lamblia (giardiasis) Original image by Arturo Gonzalez, CINVESTAV, Mexico. Used with permission of Javier Ambrosio, UNAM, Mexico

6 Giardia lamblia u Giardia lamblia trophozoites live in the small intestine of the host. u 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."

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8 B. Indicator bacteria for Drinking Water: u Indicator microorganisms are used to indicate an increased risk of pathogen contamination due to fecal contamination. u 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.

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

10 Characteristics of coliforms: u Aerobic or facultative, u Gram-negative, u Non-spore forming, u Bacilli, u which ferment lactose to form acid and/or gas within 48 hours at 35 o C.

11 More specific coliforms: u Coliforms are often found naturally in soil, water, plants, etc. u Fecal coliforms are a more specific coliforms that usually come from feces. u E. coli is the most specific indicator

12 Guidelines and methods for enumerating coliforms: u EPA guidelines for coliforms in drinking water are < 1 CFU/100 ml. u Tests used to isolate and enumerate coliforms in water include: –m-Endo media –m-FC media –MUG media

13 C. Other indicators for drinking and recreational water C. Other indicators for drinking and recreational water u Limitation of Total coliform as drinking water microbial indicator –Ubiquitous. –Less resistant to traditional disinfection. –Proliferate in the biofilms of water distribution systems

14 u Limitation of Fecal coliforms –Klebsiella pneumoniae –Less resistant to traditional disinfection. u Limitation of E. coli –Less resistant to traditional disinfection.

15 Microbial Indicators for Recreational Water u Total coliform? u Fecal coliform? –Average 200 MPN/100 ml u E. Coli (fresh water)? –Average 126 MPN/100 ml. u Enterococci (salt water) –Average 35 MPN/100 ml.