Biology 261

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Biology 261
2011-12-05 10:25:01
Chapter 35

Chapter 35
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  1. Define BOD, coliforms, cyst, filtration, potable, gray water and wastewater.
    • - BOD: a relative quantities of oxygen required by
    • microorganism to completely oxidize organic matter in water.

    • - Coliforms: facultatively aerobic, gram-negative,
    • non-spore-forming, lactose-fermenting bacteria.

    • - Cyst: an infectious form of a protest that is
    • encased in a thick-walled, chemically and physically resistant coating.

    • - Filtration: the removal of suspended particles from
    • water by passing it through one or more permeable membranes or media (ex. Sand,
    • anthracite, or diatomaceous earth)

    - Potable: drinkable; safe for human consumption

    • - Wastewater: liquid derived from domestic sewage or
    • industrial sources which cannot be discarded in untreated form into lakes or
    • streams.
  2. Name three organisms that are coliforms. Why are coliforms
    indicator organisms? What are other possible indicator microorganisms?
    - E. coli, Enterobacter spp., and Klebsiella pneumonia.

    - Coliforms are useful indicators of water contamination because many of them inhabit the intestinal tract of humans and other animals in large numbers, thus, their presence in water indicates fecal contamination.
  3. How are the MPN test or membrane filter procedures done and interpreted. What do they detect? What would E. coli look like growing on the EMB medium?
    - The most-probable-number (MPN) procedure employs liquid culture medium in test tubes to which samples of drinking water re added. Growth in the culture vessels indicates microbial contamination of the water supply.

    - The membrane filter (MF) procedure, at least 100 ml of the water sample is passed through a sterile membrane filter, trapping any bacteria on the filter surface. The filter is placed on a plate of eosin-methylene blue (EMB) culture medium, which is selective for coliform organisms. Following incubation, coliform colonies are counted, and from this value the number of coliforms in the original water sample can be calculated.
  4. What are the safe water standards in the US?
    - Safe water standards: not to exceed (1) 1/100 ml as a mean all samples per month, (2) 4/100 ml in more than one sample if fewer than 20 are examined per month, or in mmore than 5% when 20 or more samples are examined per month.
  5. What is biochemical oxygen demand and how is it
    used in wastewater treatment? What are the stages in wastewater and sludge treatment and what happens with various contaminants at each stage?
    • - Biochemical Oxygen Demand (BOD) is relative quantities of oxygen required by microorganisms to
    • completely oxidize organic matter in water.

    -Units the efficiency of treatment is expressed in.
  6. What are additional stages required to make
    treated water potable?
    • Treated wastewater is not potable.

    • • Additional treatments to (1) reduce turbidity and (2) disinfect, (3) eliminate taste and odor and (4)
    • reduce nuisance chemicals like Fe and Mn.

    • • Stages: (1)sedimentation basin, (2) clarifier or coagulation basin, (3) filtration, (4) chlorination (residual amount 0.2-0.6 mg/ml), (5) storage or distribution
    • system.
  7. What microorganisms are most commonly responsible for disease outbreaks due to drinking water contamination? What is a type of a disease most commonly acquired from recreational waters?
    - Giardiasis, Cryptosporidiosis, Legionella, and Escherichia coli

    - Common recreational water disease: Gastroenteritis, Dermatitis, Meningoencephalitis
  8. What are the factors responsible for cholera pathogenicity? How is cholera prevented and treated? What causes the “rice water” stools associated with cholera?
    • Two biotypes: classic and El Tor. Only serotypes O1 and O139 cause cholera.

    •5 million cases since 1961 with over 250,000 deaths.

    • Worldwide. In 1999, 400,000 cases and 9,000 deaths. In 2005, 132,00 cases and 2,272 deaths. In 2008, 190,130 cases, 5,143 deaths.

    • • USA. Sporadic outbreaks are reported along the Gulf Coast. Largest outbreak -16 cases. Mostly seafood
    • related.

    • Major factor in pathogenicity is enterotoxin.

    • Detection in stool microscopically, specific symptoms.

    • Treatment: electrolyte replacement therapy, streptomycin and tetracycline. If treated mortality ~1%.
  9. What are two other important Vibrio infections
    that are transferred through water?
    • Vibrio vulnificus - vibremia

    – 95% of all seafood-related death in the US.

    • – Fatality rates 60% for raw seafood consumption and 20-25% for wound infections. Fortunately, never
    • epidemic.

    – Gastroenteritis - accompanied by other species.

    • Vibrio parahaemolyticus

    – The largest outbreak in Port Allen, LA: 1,133 persons of 1,700 attending.

    – Gastroenteritis with diarrhea
  10. Why are protozoans often associated with
    waterborne diseases in developed countries? What are their natural reservoirs?
    How could these diseases be prevented?
    • Giardia lamblia

    • – Natural reservoirs are
    • carnivores and rodents.

    • – Ingestion of cysts leads
    • to gastroenteritis.

    • – Detection of cysts
    • microscopically and ELISA.

    – Treatment metronidazole, quinacrine, furozolidone.

    • Cryptosporidium parvum

    – Infects many warm-blooded animals.

    – Largest case in Milwaukee (WI): 400,000 people develop diarrhea, few died from complications.

    – Ingestion of oocysts leads to a disease. Cysts are highly resistant to sterilization.

    – Detection of cysts in the stool. No treatment is needed for healthy individuals
  11. How is a trophozoite different from a cyst?
    • - Cyst: an infectious form
    • of a protest that is encased in a thick-walled, clemically and physically resistant coating.
  12. What is Legionaires’ disease? How does infection with legionellosis occur? How is it diagnosed and treated?
    • Normal habitats are freshwater environment and soil.

    • Infect individuals through aerosols, particularly aerosols created by cooling/heating system.

    • • Legionella pneumophila causes pneumonia through
    • invasion of alveolar macrophages and monocytes.

    • Some serotypes may lead to a mortality rate of 10%.

    • Diagnostics: culturine and antibody test.

    • Treatment with rifampin and erythromycin.
  13. Which microorganisms cause amebiasis and typhoid
    • Typhoid fever, Salmonella enterica serovar Typhi.

    • Enteroviruses, Norwalk-like viruses and hepatitis A virus.

    • Amebiasis caused by Entamoeba hystolytica.

    – Produces cysts, anaerobic

    – Many infections are asymptomatic but may lead to dysentery. If not treated, trophozoites can invade liver, lungs and brain.

    – Annually 100,000 individuals die worldwide.

    – Treatment with dihydroemitine and diloxanide furoate.

    • Diagnosis: cysts in the stool and
    • antibodies by ELISA

    • Naegleria fowleri, an amoeba

    – Enters through nose and goes directly to the brain

    – Meningloencephalitis leads to death within a week.

    – All cases (12 from 1999 to 2003) have been lethal.

    – Prevetion: avoid of swimming in warm shallow waters in summer.