BIOL 261: CH. 33 - WATERBORNE AND FOODBORNE BACTERIAL AND VIRAL DISEASES

Botulism

food poisoning due to ingestion of food containing botulinum toxin produced by Clostridium botulinum

Coliforms

gram-negative, nonsporulating, facultatively aerobic rods that ferment lactose with gas formation within 48 hours at 35 degrees Celsius

Food infection

a microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth of the pathogen in the hosT

Food poisoning (food intoxication)

a disease caused by the ingestion of food that contains preformed microbial toxin

Food spoilage

a change in the appearance, smell, or taste of a food that makes it unacceptable to the consumer

Listeriosis

a gastrointestinal food infection caused by Listeria monocytogenes that may lead to bacteremia and meningitis

Nonperishable foods

foods of low water activity that have an extended shelf life and are resistant to spoilage by microorganisms

Pasteurization

the use of controlled heat to reduce the microbial load, including both pathogens and spoilage organisms, in heat-sensitive liquids

Perishable foods

fresh foods generally of high water activity that have a very short shelf life because of spoilage by microbial growth

Potable

in water purification, drinkable; safe for human consumption

Salmonellosis

enterocolitis or other gastrointestinal disease caused by any of several subspecies of the bacterium Salmonella

Semiperishable foods

foods of intermediate water activity that have a limited shelf life because of their potential for spoilage by growth of microorganisms

What role does water play in the transmission of disease?

Vehicle that can carry pathogen

What happens if you ingest contaminated water?

Can make you sick

What do safe drinking water standards aim to prevent?

Ingestion of pathogens through contaminated water

What does water quality testing commonly screen for?

Coliforms

What are coliforms?

Gram-negative rods that live in the intestines and indicate fecal contamination

Give examples of coliform bacteria.

E. coli, Enterobacter, Klebsiella pneumoniae

What are coliforms used as in microbiology?

Indicator organisms

Are all coliforms fecal in origin?

No

Which organism is a key fecal coliform?

Escherichia coli

What is the purpose of the membrane filtration test?

to filter water so bacteria are trapped on the filter, then placed on EMB agar

What does EMB agar select for?

Gram-negative rods

What does EMB agar differentiate?

lactose fermenters

What indicates the presence of E. coli on EMB agar?

green metallic sheen

Why is E. coli used in water testing?

indicator organism for fecal contamination

What does the MPN test estimate?

most probable number of coliforms in a 100 mL water sample

What medium is used in the MPN test?

Lauryl Tryptose Broth

What result in Lauryl Tryptose Broth indicates a positive test?

gas production

What pathogens might be present in contaminated water besides coliforms?

Salmonella, Shigella, Vibrio

Do Salmonella, Shigella, and Vibrio ferment lactose?

no

What defines an infection?

organism is growing in the body

What defines an intoxication?

exotoxin is causing damage

What is the shape and Gram stain of Vibrio cholerae?

G- curved rod

Where does Vibrio cholerae naturally live?

brackish water

What food is commonly associated with Vibrio cholerae infection?

raw oysters

How does cholera toxin affect the small intestine?

blocks Na+ absorption --> causes water to enter intestines

What are the symptoms caused by Vibrio cholerae?

massive diarrhea, rice water stools, epithelial cells in stool

What media is used to culture Vibrio cholerae?

TCBS agar

What makes TCBS agar selective and differential for Vibrio cholerae?

selective for Vibrio species, differential because it ferments sucrose

What is the primary treatment for cholera?

oral rehydration and electrolyte replacement therapy

What is the key diagnostic test for cholera?

presence of Vibrio cholerae bacilli in the “rice water” stools of patients

Where is Legionella commonly found?

AC cooling tower

How is Legionella transmitted?

via contaminated water aerosols; inhaling water droplets

Is Legionella spread from person to person?

no, only through contaminated water sources

What type of agar does Legionella pneumophila grow on?

buttered charcoal yeast extract agar (BCYE agar)

Where is the Legionellosis pathogen often found?

improperly sanitized cooling towers and evaporative condensers of large air conditioning systems

Is Legionellosis spread from person to person?

no, it is not spread person to person

What is the treatment for Legionellosis?

antibiotics

What is typhoid fever transmitted through?

feces-contaminated water

Does the bacterium that causes typhoid fever ferment lactose?

no

What organism causes typhoid fever?

Salmonella typhi

What type of illness is caused by Salmonella typhi?

infection

Which Salmonella species is associated with turtles and chickens?

Salmonella enteritica

What is the Gram reaction and shape of Salmonella and Shigella?

Gram-negative rods

Do Salmonella and Shigella ferment lactose?

no

What is a common setting for norovirus outbreaks?

cruise ships

How is norovirus commonly transmitted?

fecal-oral route

How can fecal contamination lead to norovirus infection?

contaminates food

What kind of diseases does norovirus cause?

enteric diseases

What are common symptoms of a norovirus infection?

excessive diarrhea and dehydration

How does norovirus spread from person to person?

easily transmitted via fecal-oral route

What are perishable foods?

foods that spoil easily and have high water content

What are examples of perishable foods?

meat, vegetables, fruits

Why do perishable foods spoil easily?

because of their high water content

What are nonperishable foods?

foods that do not spoil easily and have low water content

What are examples of nonperishable foods?

rice, dried beans, flour

What characteristics define the chemical properties of foods?

moisture level, nutrient content, acidity or alkalinity, and other factors

What is the goal of food preservation?

to slow the growth of microorganisms that spoil food or cause foodborne disease

What is the recommended temperature for refrigeration to prevent food spoilage?

4 degrees Celsius

What is the typical temperature of a freezer used for food preservation?

-15 degrees Celsius

What does heating do to proteins in microbes?

denatures proteins

What is pasteurization used for?

heat-sensitive foods

Why is temperature increased during pasteurization?

to kill off pathogenic bacteria

What food preservation method is similar to autoclaving?

canning food

What does canning food involve?

increased pressure and increased temperature

What is the goal of using pressure and temperature in canning?

sterilization

What kind of microbial structure can survive normal heating but is targeted in canning?

endospores

Which bacterium forms endospores and causes botulism?

Clostridium botulinum

What kind of environment does Clostridium botulinum prefer?

anaerobic

What disease is caused by Clostridium botulinum?

botulism

What does the exotoxin from Clostridium botulinum do?

blocks release of ACh (acetylcholine)

What is the result of blocked ACh release by the exotoxin?

flaccid paralysis

How does dehydration preserve food?

removes water

Why does removing water prevent microbial growth?

no water, no growth

What do preservatives do?

inhibit bacterial or fungal growth

What type of radiation is used in food irradiation?

gamma rays

What is the purpose of gamma rays in food irradiation?

sterilize the product

What is produced during fermentation that inhibits microbial growth?

acids and alcohols

Why can't bacteria grow during fermentation?

low pH and lack of sugar

What happens to sugar during fermentation?

converted into acid and alcohols

Which types of bacteria are important in the fermented food industry?

lactic acid bacteria, propionic acid bacteria, acetic acid bacteria

What type of bacteria produces acetic acid from ethanol?

Acetobacter

What acid does Acetobacter produce from ethanol?

Acetic acid

What is the percentage of acetic acid in vinegar?

3%

What is the source of ethanol that Acetobacter converts to acetic acid?

Alcoholic drinks like wine and beer

What is the ethanol content like in distilled alcohol compared to regular alcohol?

Higher ethanol content

What type of organism is E. coli O157:H7?

pathogen

What classification is E. coli O157:H7 considered under?

serum type

What does the "O" in E. coli O157:H7 refer to?

somatic antigen