chapter 7 water micro Flashcards
Potable clean water:
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
Biofilms=
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
Freshwater Microbiota
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
In the limnetic zone: areas with sufficient oxygen contain pseudomonads and species
In the limnetic zone: areas with sufficient oxygen contain pseudomonads and species
of Cytophaga, Caulobacter, and Hyphomicrobium.
Deeper waters of the profundal and benthic zones, have low oxygen concentrations
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.
The sediment in the benthic zone includes bacteria such as:
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.
Seawater Microbiota
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
aquatic microorganisms
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,
a. Waterborne diseases :
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 (
b. Water washed diseases:
Diseases caused by poor personal hygiene, skin and
eye contact with contaminated water
These include scabies, trachoma, typhus, and other diseases
c-Water-based diseases:
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
d-Water -related insect vector diseases:
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
Waterborne Pathogens
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 .
Microbes in water include:
Bacteria
Virus
Protozoa
Waterborne pathogens:
Some common pathogens:
Salmonella typhi Escherichia coli Vibrio cholera Pseudomonas aeruginosa Shigella spp. Yersinia enterocolitica Cryptosporidium Giardia lamblia Entamoeba Toxoplasma Norwalkvirus , Hepatitis A virus
A. Escherichia coli O157:H7
-
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.
B
Helicobacter pylori
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.
B Helicobacter pylori ( cont’d
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;
C
Mycobacterium avium complex (MAC)
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
C
Mycobacterium avium complex (MAC 2
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
D
Vibrio cholera
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.
E
Salmonella spp
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.
E Salmonella spp (cont’d)
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.
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.
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.
G. Francisella tularensis
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
G.
Francisella tularensis (
2
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
Protozoan parasites
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)
pp A
Cryptosporidium
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
B
Cyclospora cayetanensis
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
B Cyclospora cayetanensis ( 2
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
C
Giardia lamblia
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.
D. Toxoplasma gondii
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
D
Toxoplasma gondii (
2
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
Enteric viruses
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
A
Coxsakie virus
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
B
Norwalk viruses
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
C
Rotavirus
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
D
Hepatitis viruses
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
It’s not practical to look only for pathogens in water supplies Ex:
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
Critera of an indicator organism:
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
Coliform bacteria ( E. coli like) are the most often
used indicator bacteria for water quality
assessment
Characteristics of Coliforms:
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.
Coliforms (cont’d)
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.
The methods of determining the presence of coliforms in
water are largely based on the lactose fermenting ability of
coliforms bacteria
Detection Methods:
MPN method The membrane filtration method MUG & ONPG media The new techniques based on the DNA
Guidelines and methods for enumerating
coliforms
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
Limitations
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
