Waterborne Pathogens: Bacteria

1. Waterborne Pathogens: Bacteria February 9th-11th, 2010

2. 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

3. 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

4. Categories of waterborne disease • Diseases contracted by ingestion of contaminated water • Escherichia coli • Shigella spp. • Vibrio cholerae • Salmonella typhi

5. 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

6. 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

7. Escherichia coli • Gram negative rods • Identified by O and H antigens • O157:H7 strains are identified by their inability to break down sorbitol

8. 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

9. Shigella • Bacterial dysentery • Four species in the genus • dystenteriae • flexneri • boydii • sonnei • Estimated 600,000 deaths per year

10. Shigella • Gram negative rods • Distinguished from E. coli by their inability to ferment lactose

11. 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

12. 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

13. 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

14. 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

15. 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

16. Salmonella typhi • Gram negative rods • Distinguished by their inability to ferment lactose

17. 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

18. 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

19. Leptospira • Spirochete • Fastidious (difficult to culture)

20. 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

21. Legionnaire’s Disease • Legionella pneumophila • Respiratory and systemic disease • Bacterium lives in water • Inhalation of water droplets leads to disease

22. Legionnaire’s Disease • Gram negative bacilli • Need cysteine in the agar to support their growth

23. 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)

24. Control of waterborne bacteria • Drinking water: • Prevention of water contamination • ADEQUATE SANITATION • Barrier methods • Treatment trains • Filtration • disinfection