Waterborne Pathogens: Bacteria February 9 th -11 th, 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 –Escherichia coli –Shigella spp. –Vibrio cholerae –Salmonella typhi

Categories of waterborne disease Diseases spread by contact with contaminated water –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 –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 –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