Lecture 15 Flashcards
Waterborne diseases
- bacterial pathogens
- cannot be eliminated
- drinking water outbreaks
- recreational water outbreaks
water quality
- most important single factor for public health
Wilmington Water
surface (cape fear river)
- groundwater (wells)
138 gallons per day
- 80 gallons of waster water
Fecal coliforms
- bacteria present in intestines of humans + animals
- indicators of water contamination (not overall water quality)
- do not survive well in water bodies so must be in large amounts to be cultured on EMB media
Coliform cultures
- membrane filter + EMB media (selects for lactose-fermenters)
- membrane filer + MI media (differentiates e. coli + other coliforms)
water purification techniques
- filtration 1906
- chlorination 1913
filtration
- physically removing bacteria from water
- effective but expensive
- better on small scales
- filters clog up and need to be replaced
chlorination
- chemically removing bacteria from water
- treatment with chlorine gas
- effective and inexpensive
foodborne diseases
- bacterial pathogens
- cannot be eliminated
food spoilage
- unappealing changes in the look, smell, and taste of food products
major food categories
perishable– fresh fruits (high water content)
semi perishable– potatoes, nuts
nonperishable– flour, sugar (low water content)
increase shelf-life + perceived quality of food
- over 3,000 chemicals used as food additives
- GRAS compounds= generally recognized as safe
High-pressure processing (HPP)
- “pascalization”
- high hydrostatic pressure kills microbes
Irradiation
- ionizing radiation kill microbes
- labelling irradiated food
– whole: label + radura
– partial (major): label
– partial (minor): none
waterborne diseases major pathogens
bacteria: vibrio cholerae and legionella pneumophila
protists: giardia intestinalis
cholera
- vibrio cholerae and gram -
- coastal and marine habitats
- 98% of cases in Africa and untreated mortality rate 25-50%
cholera pathogenesis and diagnosis
- caused by ingestion of contaminated water or food
- v. cholerae attaches to wall of the small intestine and produces cholera toxin
- diagnosis: presence of v. cholerae cells in feces
cholera prevention and treatment
- vaccine for some strains but only provides short term immunity
- maintain adequate sewage treatment and safe drinking water
- treatment: fluid & electrolyte replacement, antibiotics (streptomycin)
Legionellosis or Legionnaires’ disease
-legionella pneumophila (lung infection)
- gram - and obligate aerobe
- found in lakes, streams, soil
- increasing incidence since 1990s
Legionellosis or Legionnaires’ disease pathogenesis
- low concentrations in nature but high in AC
- aerosol travel then leads to infection in lungs
- mild infection: fever and cough
- severe infection: pneumonia and immune compromised host
Legionellosis or Legionnaires’ disease diagnosis, prevention, and treatment
- diagnosis: culture from body fluids
- improved maintenance of AC
- killed by >63C and hyperchlorination
- no vaccine, use antibiotics (IV erythromycin)
Giardiasis or backpacker’s diarrhea
- giardia intestinalis
– flagellated protest
– trophozoite and cyst stages - mammalian parasite
Giardiasis or backpacker’s diarrhea pathogenesis, symptoms, and diagnosis
- ingestion of giardia cysts (shed in feces of infected animals)
- ubiquitous in natural waters
- diarrhea and gas (1-2 weeks or up to a month)
- diagnosis through microscopy and immunoassays
Giardiasis or backpacker’s diarrhea prevention and treatment
- water filtration (cysts are resistant to chlorine treatment)
- antibiotics with variable effectiveness
