Waterborne Pathogens:
Bacteria
February 9th-11th, 2010
Bacterial pathogens in water
• Important causes of waterborne disease
• We don’t always know the distribution of causes
of diarrheal disease, but bacteria are major
contributors
• Can be endemic or epidemic
• Epidemic disease is often found where people
are crowded, hygiene and sanitation are poor
– Disaster situations
– Displaced populations
Categories of waterborne disease
• Diseases contracted by ingestion of
contaminated water
• Most are diarrheal diseases, but not all
• The largest burden of these diseases is in
countries that lack water infrastructure
• But they are NOT gone even in countries
that have infrastructure
Categories of waterborne disease
• Diseases contracted by ingestion of
contaminated water
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Escherichia coli
Shigella spp.
Vibrio cholerae
Salmonella typhi
Categories of waterborne disease
• Diseases spread by contact with
contaminated water
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Bathing, wading
Contact with floodwaters
Pathogen lives naturally in the water
Leptospira
• Diseases spread by inhalation of
contaminated water
– Aerosols
– Legionella
Escherichia coli
• Are both commensal (harmless) and
pathogenic types
• There are several distinct types of
pathogenic E. coli
• Pathogenic process differs between them
• Some have toxins, some other virulence
factors
• Fecal-oral and person-to-person
transmission
Escherichia coli
• Gram negative rods
• Identified by O and H antigens
• O157:H7 strains are identified by their
inability to break down sorbitol
Escherichia coli
• Example: O157:H7
• Belongs to the enterohemorrhagic group
• Cattle are the major reservoir
– Found in their intestinal tracts
• Toxin producer
– Shiga and Vero toxins
• Occurs as both a foodborne and waterborne
pathogen
• Major risk group is children: hemolytic uremic
syndrome
Shigella
• Bacterial dysentery
• Four species in the genus
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dystenteriae
flexneri
boydii
sonnei
• Estimated 600,000 deaths per year
Shigella
• Gram negative rods
• Distinguished from E. coli by their
inability to ferment lactose
Shigella
• Profuse diarrhea and dehydration
• Humans are the reservoir
• Fecal-oral and person-to-person
transmission
• A disease of crowded conditions and poor
hygiene
• Lack of sufficient clean water for adequate
hygiene
• Handwashing is a crucial control measure
Vibrio cholerae
• Cholera
• There are other species that are causes of
foodborne disease
• Cause of epidemic diarrheal disease
• Crowding, poor sanitation, lack of water
treatment
• Currently: Zimbabwe
• Reservoir: marine environments
Vibrio cholerae
• Gram negative curved rods
• Distinguished by their salt tolerance and
ability to ferment sucrose
• Divided into biotypes; epidemic causes
are O1 and O139
Vibrio cholerae
• Fecal-oral and person-to-person
transmission
• There are asymptomatic carriers who can
transmit disease
• Bacteria produces a toxin that causes
severe fluid and electrolyte loss from the
intestine
• Can kill by severe dehydration
• Characteristic “rice water” stool
• Treatment: Oral rehydration therapy
Salmonella typhi
• Typhoid fever
• Other species cause foodborne disease
• Typhoid can be food or water borne
• Mostly in developing world
• 200,000 deaths per year
Salmonella typhi
• Gram negative rods
• Distinguished by their inability to ferment
lactose
Salmonella typhi
• Fecal-oral and person-to-person
transmission
• Humans are the reservoir
• Asymptomatic people in a chronic carrier
state can spread disease
• Vaccination is only done for travelers
• Again, a disease of inadequate water
treatment and sanitation
Leptospira
• Leptospirosis
• Systemic bacterial infection; can be fatal
• Zoonotic disease
• Several pathogenic species
• Infection enters through broken skin
– Often from contact with contaminated natural
water sources
– Contact with floodwaters after disasters also a
common transmission route
• Very rarely person-to-person
Leptospira
• Spirochete
• Fastidious (difficult to culture)
Leptospira
• Endemic in tropical areas
– Both urban and rural
• Occupational hazard for rice and
sugarcane field workers
• Animals are reservoirs
– Often dogs and rats
– Shed organism into water in their urine
Legionnaire’s Disease
• Legionella pneumophila
• Respiratory and systemic disease
• Bacterium lives in water
• Inhalation of water droplets leads to
disease
Legionnaire’s Disease
• Gram negative bacilli
• Need cysteine in the agar to support their
growth
Legionnaire’s Disease
• Reservoirs: potable water systems
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Cooling towers
Water distribution systems
Fountains
Humidifiers
• Like warm, stagnant water (up to 42°C)
• Significant hospital-acquired pathogen
– Can live in hospital distribution systems
– Aersolized by showers
– Immunocompromised patients are susceptible
• Control by superchlorination and high temp
(>50°C)
Control of waterborne bacteria
• Drinking water:
• Prevention of water contamination
– ADEQUATE SANITATION
• Barrier methods
– Treatment trains
– Filtration
– disinfection