chapter 7 water micro

Question 1

Potable clean water:

Answer 1

water that’s free of all objectionable
material, including pathogens, tastes, colors, toxins,
radioactive materials, oils…
It can contain high concentration of some minerals (such as
calcium and magnesium) and gases like CO2

Question 2



Biofilms=

Answer 2

microbes that adhere to surfaces and
accumulate as biofilms on solid surfaces in contact
with water.

The concentration of bacteria in water is
proportional to the amount of organic material in
the water

Question 3

Freshwater Microbiota

Answer 3

Microbial populations of freshwater bodies tend to be mainly affected by the
availability of light and oxygen. Most aquatic bacteria tend to grow on surfaces

Question 4

In the limnetic zone: areas with sufficient oxygen contain pseudomonads and species

Answer 4

In the limnetic zone: areas with sufficient oxygen contain pseudomonads and species
of Cytophaga, Caulobacter, and Hyphomicrobium.

Question 5

Deeper waters of the profundal and benthic zones, have low oxygen concentrations

Answer 5

Deeper waters of the profundal and benthic zones, have low oxygen concentrations
and less light, contain purple and green sulfur bacteria .These bacteria are anaerobic
organisms that metabolize H2S to sulfur and sulfate in the bottom sediments of the
benthic zone.

Question 6

The sediment in the benthic zone includes bacteria such as:

Answer 6


Desulfovibrio that use sulfate (SO4 —-) as an electron acceptor and reduce it to

Methane producing bacteria: in swamps, marshes, or bottom sediments, they produce
methane gas.

Clostridium species are common in bottom sediments and may include botulism organisms,
particularly those causing outbreaks of botulism in waterfowl.

Question 7

Seawater Microbiota

Answer 7


Seafloor sediments have been found to have large populations of microorganisms
mostly Archaea, which adapt well to environmental stresses and have low energy
requirements

These microbes produce huge amounts of methane gas that could be
environmentally damaging if it is released into the atmosphere.

In the upper, relatively sunlit waters of the ocean, photosynthetic cyanobacteria of
the genera Synechococcus and Prochlorococcus are abundant.

Some photosynthetic bacteria fix carbon dioxide to form organic matter that is eventually
released as dissolved organic matter and is used by the ocean’s heterotrophic bacteria.

Others fixe nitrogen and help replenish the nitrogen that is lost as organisms sink to oceanic
depths.

Pelagibacter ubique, metabolize the waste products of photosynthetic populations

Question 8

aquatic microorganisms

Answer 8


Bacteria serve as food for larger consumers such as protozoa

Much of the carbon dioxide and mineral nutrients released by the metabolic activity
of bacteria, protozoa, and zooplankton is recycled into the photosynthetic
phytoplankton.

In waters below about 100 meters, Archaea begin to dominate microbial life. These
organisms are well adapted to the cool temperatures and low oxygen levels of oceanic
depths. Their carbon is primarily derived from dissolved CO2.

Luminescent bacteria :microbial bioluminescence, or light emission,

Question 9

a. Waterborne diseases :

Answer 9

diseases caused by ingestion of water contaminated by
human or animal excrement, which contain pathogenic microorganisms

They include cholera, typhoid, amoebic and bacillary dysentery and other
diarrheal diseases (Giardiasis (Protozoan), Cryptosporidiosis (Bacteria),
Campylobacteriosis (Bacteria), Shigellosis (Bacteria), Viral Gastroenteritis
(Virus), Cyclosporiasis (

Question 10

b. Water washed diseases:

Answer 10

Diseases caused by poor personal hygiene, skin and
eye contact with contaminated water

These include scabies, trachoma, typhus, and other diseases

Question 11

c-Water-based diseases:

Answer 11

diseases caused by parasites found in intermediate
organisms living in contaminated water
* They are passed to humans mainly through ingestion or skin contact
* Includes Schistosomiasis and Dracunculiasis

Question 12

d-Water -related insect vector diseases:

Answer 12

Water-related diseases are caused
by insect vectors, especially mosquitoes, that breed or feed near contaminated
water.
 Include dengue, filariasis, malaria, onchocerciasis, trypanosomiasis and yellow
fever

Question 13

Waterborne Pathogens

Answer 13

Most waterborne pathogens may be classified as viruses, bacteria, or
protozoa

They cause primarily intestinal diseases, leaving the host in fecal material,
contaminating the water supply, and then entering the recipient by
ingestion.

Their survival period in water varies widely and is influenced by many
factors such as salinity, temperature, etc..

It may be generalized that cellular viruses last longer than bacteria while
protozoa can extend their survival time by encystation .

Question 14

Microbes in water include:

Answer 14

Bacteria
Virus
Protozoa

Question 15

Waterborne pathogens:

Some common pathogens:

Answer 15


Salmonella typhi

Escherichia coli

Vibrio cholera

Pseudomonas aeruginosa

Shigella spp.

Yersinia enterocolitica

Cryptosporidium

Giardia lamblia

Entamoeba

Toxoplasma

Norwalkvirus , Hepatitis A virus

Question 16

A. Escherichia coli O157:H7

Answer 16

-
Infection with this organism can cause severe bloody diarrhea with
abdominal cramping
-
In small children and the elderly fluid replacement is of the highest
importance for full recovery
-
A common more serious complication of infection with E.coli
O157:H7 is hemolytic uremic syndrome (HUS) where there’s a loss of
red blood cells and kidney failure; in severe cases HUS can cause
permanent kidney damage
-
E. coli O157:H7 has been shown to survive similarly to typical E.coli
strains under routine drinking water conditions.

Question 17

B

Helicobacter pylori

Answer 17


It has been cited as a major agent of gastritis and has been implicated
in the pathogenesis of peptic and duodenal ulcer disease

It has also been associated with development of gastric carcinoma
Eurogast study group 1993)

H. pylori is commonly transmitted person to person by saliva.

The bacteria can also be spread by fecal contamination of food or
water.

Question 18

B
Helicobacter pylori ( cont’d

Answer 18


Persons living in low socio economic conditions have been shown to
have high prevalence of H. pylori.

In developing countries, a combination of untreated water, crowded
conditions, and poor hygiene contributes to higher H. pylori prevalence.

Inadequate sanitation practices, low social class, and crowded or high
density living conditions seem to be related to a higher prevalence of H.
pylori infection

Most people become infected as children, and parents and siblings seem
to play a primary role in transmission.

The water source might be an important risk factor than socio
economic status in acquiring H. pylori infection;

Question 19

C

Mycobacterium avium complex (MAC)

Answer 19


MAC has been isolated from natural water and drinking water
distribution systems from several countries

Members of the MAC are considered opportunistic human
pathogens

There has been a dramatic increase in the number of AIDS
patients infected with MAC

Question 20

C

Mycobacterium avium complex (MAC 2

Answer 20


Evidence of environmental transmission of MAC includes:
increased frequency of MAC in gastrointestinal tract of advanced
AIDS patients and gastrointestinal symptoms (nausea, vomiting
and diarrhea)

M. avium strains from infected AIDS patients have been shown to
be genetically related to isolates recovered from water to which the
patients were exposed through drinking or bathing

However, the control of MAC is very difficult as they are extremely
resistant to disinfection methods and have been shown to survive
10 mg/l of chlorine

Question 21

D

Vibrio cholera

Answer 21


A lack of sanitation and increasing in population often with limited
access to clean water has brought about numerous disease
outbreaks. It causes diarrhea and vomiting

Exp : in the Americas in 1995 about 1 million people were infected by
V. cholerae and about 10000 deaths.

Increasing pollution in of coastal waters in Hong Kong was the
principal cause of Hon Kong outbreaks

Inadequate disinfection or the lack of disinfection has contributed
significantly to the spread of cholera throughout Africa and Latin
America.

Question 22

E

Salmonella spp

Answer 22


Salmonellosis incidence (food poisoning) is low and peaks seasonally in
mid to late summer due to favorable conditions for food borne
salmonella.

Salmonella spp. Are carried by humans (1 4% of population), farm
animals (13 17% incidence) and wild animals.

This disease is caused by members of the genus Salmonella, a Gram
negative rod of the Enterobacteriaceae family. These bacteria are
intestinal inhabitants of a wide range of animals including birds,
mammals, reptiles.

In humans these bacteria induce gastroenteritis; diarrhea, abdominal
cramps, fever and vomiting.

Question 23

E
Salmonella spp (cont’d)

Answer 23


Most Salmonella spp. cause gastrointestinal diseases, while one, which is
strictly a human pathogen, causes typhoid.

The disease is transmitted by fecal oral route; contaminated food or water.

Most cases of Salmonellosis are self limiting, but babies and the elderly can
die from the disease

Many of the strains are resistant to numerous antibiotics

A carrier state is common.

To avoid this disease possibly contaminated food like poultry and beef
should be sufficiently heated to kill any Salmonella anywhere within the
meat. Products made from uncooked egg (e.g. hollandaise sauce) should be
avoided unless heated.

Question 24

F
Shigella spp Most shigellosis and salmonellosis epidemics in developed countries are food
borne but a few are caused by drinking water. Transmission by drinking water is
still the major route of infection in underdeveloped countries.

Answer 24


Gram negative bacterial intestinal pathogen

Transmitted by the fecal oral route via contaminated water and food.

Reservoir: mainly human

It is a major cause of infant mortality around the world.

It produces diarrhea, often with bloody stools and abdominal cramps.

protein toxin is produced by the organism

Treatment involves antibiotics and oral rehydration therapy, but drug resistance
is a problem

Prevention includes sanitary procedures and proper preparation and cooking of
foods.

Question 25

G. Francisella tularensis

Answer 25


Gram ve, non motile, coccobacillus, strict aerobe, lipid capsule, fastidious

Tularemia

Tularemia is passed principally by ticks, rodents and direct contact with
sewage. Water contamination occurs from rodents. The disease spreads via
the lymphatics and bloodstream. It grows intracellulary and causes lesions in
the lungs, liver, spleen and brain.

Most often ulcer on the hand withswelling of the regional lymph nodes

Inhalation: pneumonic disease or primary systemic (typhoidal) syndrome

Ingestion: abdominal pain, diarrhea and vomiting

Occurrence: North America, Europe, China, Japan.

Reservoir: numerous wild animals: rabbits, some domestic animals

Question 26

G.
Francisella tularensis (
 2

Answer 26

Mode of transmission:

Inoculation of skin

Bite of arthropods

Handling or ingesting undercooked rabbit

Drinking contaminated water

Inhalation of dust from contaminated soil

Incubation period: 2 10 days, usually 3 days

Preventive measures

Educate the public to avoid bites of flies, mosquitoes, and ticks

Avoid drinking, bathing, swimming or working in untreated water

Use gloves and masks when skinning or handling animals especially
rabbits and when culturing F. tularensis

Cook the meat

Question 27

Protozoan parasites

Answer 27


The emerging protozoa associated with waterborne diseases
all produce an oocyst or spore like structure that is the
infectious stage.

These life stages are very resistant to routine disinfection in
drinking water

Most are associated with animals (with the exception of
Cyclospora) therefore the control of animal wastes is as
equally important as the control of human wastes

The detection of these protozoa is by general microscopy and
actually by the new technique PCR (Polymerase chain
reaction)

Question 28

pp A

Cryptosporidium

Answer 28


It causes severe watery diarrhea lasting several days to a
week

It has been described in the literature as the most
significant cause of waterborne disease in these days.

New methods are available for the detection and
characterization of this parasite like cell cultures
technique and PCR

Question 29

B

Cyclospora cayetanensis

Answer 29


It’s a single cell coccidian protozoan that has been implicated as
an agent of prolonged watery diarrhea in humans

Humans are the only known hosts

It’s now known to be an obligate parasite of immunodeficient and
immunocompetent:

In an immunocompromised person the parasite can cause profuse,
watery diarrhea lasting several months.

The infection is less severe in immunocompetent patients

Question 30

B
Cyclospora cayetanensis ( 2

Answer 30


Symptoms may range from no symptoms to abdominal
cramps nausea vomiting and fever lasting from 3 25days

Possible contamination is due to the irrigation by human
wastes

Identification by microscopy and PCR

Question 31

C

Giardia lamblia

Answer 31


Giardia lamblia (or intestinalis ) is endemic in the US, and is the
most common identified water borne illness in the US. It tends to
infect individuals who spend a lot of time in the woods, but it also can be
contracted from improperly treated city water and from person to
person

It is a world wide pathogen with an incidence often exceeding 10% in
developing countries.

Symptoms vary but often include inflammation of the bowel, diarrhea,
cramps, fatigue, vomiting and weight loss.
Long term carriers are common.

Recovery, followed by repeated attacks may occur.

The reservoirs include dogs, cats, raccoons and humans.

Prevention includes boiling the water or treating it with chlorine
or iodine; but it may take several hours in cold water to kill the
cyst with these chemicals. It can be treated with anti protozoan
drugs.

Question 32

D. Toxoplasma gondii

Answer 32


It’s considered a tissue protozoan of cats that become
infected mainly from eating infected rodents or birds or
from feces from infected cats

The symptoms of infection include flu like symptoms, with
swollen glands in the neck and most people recover
without treatment

Question 33

D
Toxoplasma gondii (
 2

Answer 33

Humans and other mammals acquire the disease the ingestion of
the oocysts (or ingestion of contaminated undercooked meat );

In the immunocompromised the infection may cause severe
disease.

The greatest risk is to the fetus from infection during pregnancy
that can lead to the death of the fetus

Several outbreaks have been associated with contaminated surface
water

Detection method for oocysts in water have not been developed
so the presence of infection was confirmed by using mouse
bioassays surveys

Question 34

Enteric viruses

Answer 34


There are several hundred enteric viruses that are potentially
important agents of waterborne diseases

Contamination of groundwater with viruses is of great concern
due to the resistant nature of the viral structure

Viruses can survive up to months in ground water and more
resistant to water disinfection than coliforms .

The new PCR techniques have shown that there’s much more
contamination than previously recognized

Question 35

A

Coxsakie virus

Answer 35


It’s associated with myocarditis

They are commonly isolated from sewage, surface waters and
ground waters

The cell culture method and PCR are applied to detect this
virus

Question 36

B

Norwalk viruses

Answer 36


They have been the cause of numerous food and waterborne
outbreaks associated with fecally contaminated shellfish,
drinking water and recreational water.

They are responsible of gastroenteritis symptoms include
vomiting diarrhea fever and in some cases respiratory illness

Question 37

C

Rotavirus

Answer 37


It’s believed that Rotavirus is responsible for the deaths of 4 5 million
persons annually world wide.

In third world countries it has been estimated that more than 125
million cases of gastroenteritis due to Rotavirus occur each year in
children

It’s the major cause of viral gastroenteritis throughout the world and
several water outbreaks have been documented.

All of the Rotavirus outbreaks have been associated with direct fecal
contamination of a water supply or suboptimal drinking water
treatment

PCR is actually the best method to detect this virus

Question 38

D

Hepatitis viruses

Answer 38


The symptoms of hepatitis A virus (HAV) include:

Fever, nausea, malaise and often with mild diarrhea.

The infected liver cells cause cytological damage, necrosis and
inflammation of the liver;

Illness usually lasts from 1 to 2 weeks but may last several months ;

That’s why control of HAV in wastewater and their elimination from
water used for irrigation of crops is a worldwide concern

Question 39



It’s not practical to look only for pathogens in water supplies Ex:

Answer 39

It’s not practical to look only for pathogens in water supplies Ex:
Cholera or Typhoid

Time consuming so the prevention of the disease would be too late

Pathogens would probably be present only in small numbers and
might not be included in tested samples

Question 40

Critera of an indicator organism:

Answer 40


Useful for all water types

Always present when pathogens are present

Not present in the absence of the pathogen

Correlated with degree of pollution

Easily detected and identified

Survive longer than the pathogen

Not dangerous to work with
Indicator Organisms

Question 41

Coliform bacteria ( E. coli like) are the most often
used indicator bacteria for water quality
assessment
Characteristics of Coliforms:

Answer 41


Aerobic or facultative
anaerobic

Gram negative,

Non spore forming bacilli,
-Lactose fermenter
to form acid and/or
gas within 48 hours
at 35 o C.

Question 42

Coliforms (cont’d)

Answer 42


Coliforms are often found naturally in
soil, water, plants, etc.

Fecal coliforms are more specific
coliforms that usually come from feces.
The predominant fecal coliform is E. coli that constitutes a
large proportion of the human intestinal population.

There are specialized tests to distinguish between fecal and
nonfecal coliforms.

Question 43

The methods of determining the presence of coliforms in
water are largely based on the lactose fermenting ability of
coliforms bacteria
Detection Methods:

Answer 43


MPN method

The membrane filtration method

MUG & ONPG media

The new techniques based on the DNA

Question 44

Guidelines and methods for enumerating

coliforms

Answer 44

EPA guidelines for coliforms in
drinking water are < 1 CFU/100 ml.

Tests used to isolate and/or enumerate
coliforms in water include:

m Endo media

m FC media

Question 45

Limitations

Answer 45


The growth of coliform bacteria embedded in biofilms on the inner
surfaces of water pipes.

Some pathogens, especially viruses and protozoan cysts and oocysts, are
more resistant than coliforms to chemical disinfection.

Chemically disinfected water samples that are free of coliforms may be
contaminated with enteric viruses which are resistant to chlorination

The cysts of Giardia lamblia and oocysts of Cryptosporidium are so resistant to
chlorination that completely eliminating them by this method is probably
impractical; mechanical methods such as filtration are necessary