Lecture 15

Question 1

Waterborne diseases

Answer 1

• bacterial pathogens
• cannot be eliminated
• drinking water outbreaks
• recreational water outbreaks

Question 2

water quality

Answer 2

• most important single factor for public health

Question 3

Wilmington Water

Answer 3

surface (cape fear river)
- groundwater (wells)
138 gallons per day
- 80 gallons of waster water

Question 4

Fecal coliforms

Answer 4

• 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

Question 5

Coliform cultures

Answer 5

• membrane filter + EMB media (selects for lactose-fermenters)
• membrane filer + MI media (differentiates e. coli + other coliforms)

Question 6

water purification techniques

Answer 6

• filtration 1906
• chlorination 1913

Question 7

filtration

Answer 7

• physically removing bacteria from water
• effective but expensive
• better on small scales
• filters clog up and need to be replaced

Question 8

chlorination

Answer 8

• chemically removing bacteria from water
• treatment with chlorine gas
• effective and inexpensive

Question 9

foodborne diseases

Answer 9

• bacterial pathogens
• cannot be eliminated

Question 10

food spoilage

Answer 10

• unappealing changes in the look, smell, and taste of food products

Question 11

major food categories

Answer 11

perishable– fresh fruits (high water content)
semi perishable– potatoes, nuts
nonperishable– flour, sugar (low water content)

Question 12

increase shelf-life + perceived quality of food

Answer 12

• over 3,000 chemicals used as food additives
• GRAS compounds= generally recognized as safe

Question 13

High-pressure processing (HPP)

Answer 13

• “pascalization”
• high hydrostatic pressure kills microbes

Question 14

Irradiation

Answer 14

• ionizing radiation kill microbes
• labelling irradiated food
  – whole: label + radura
  – partial (major): label
  – partial (minor): none

Question 15

waterborne diseases major pathogens

Answer 15

bacteria: vibrio cholerae and legionella pneumophila
protists: giardia intestinalis

Question 16

cholera

Answer 16

• vibrio cholerae and gram -
• coastal and marine habitats
• 98% of cases in Africa and untreated mortality rate 25-50%

Question 17

cholera pathogenesis and diagnosis

Answer 17

• 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

Question 18

cholera prevention and treatment

Answer 18

• vaccine for some strains but only provides short term immunity
• maintain adequate sewage treatment and safe drinking water
• treatment: fluid & electrolyte replacement, antibiotics (streptomycin)

Question 19

Legionellosis or Legionnaires’ disease

Answer 19

-legionella pneumophila (lung infection)
- gram - and obligate aerobe
- found in lakes, streams, soil
- increasing incidence since 1990s

Question 20

Legionellosis or Legionnaires’ disease pathogenesis

Answer 20

• 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

Question 21

Legionellosis or Legionnaires’ disease diagnosis, prevention, and treatment

Answer 21

• diagnosis: culture from body fluids
• improved maintenance of AC
• killed by >63C and hyperchlorination
• no vaccine, use antibiotics (IV erythromycin)

Question 22

Giardiasis or backpacker’s diarrhea

Answer 22

• giardia intestinalis
  – flagellated protest
  – trophozoite and cyst stages
• mammalian parasite

Question 23

Giardiasis or backpacker’s diarrhea pathogenesis, symptoms, and diagnosis

Answer 23

• 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

Question 24

Giardiasis or backpacker’s diarrhea prevention and treatment

Answer 24

• water filtration (cysts are resistant to chlorine treatment)
• antibiotics with variable effectiveness