Download 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
A.Waterborne microbial pathogens
Microbiology 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
Cryptosporidium parvum
Crypto “Ooc
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.