Food Microbiology Exam 3

What is the significance of BoNT in Clostridium botulinum?

BoNT is formed at the end of the log phase.

When do spores form in Clostridium botulinum?

Spores form in the stationary phase.

What triggers sporulation in Clostridium perfringens?

Sporulation is triggered during the exponential phase by transcription factors encountering Pi in the intestine.

At what stage is CPE produced in Clostridium perfringens?

CPE is produced at a late stage of sporulation.

What type of spores does Bacillus cereus produce?

Bacillus cereus produces hydrophobic spores.

What role do exosporium and spore appendages play in bacterial spores?

They help adhere to surfaces.

What is the function of the space between the exosporium and coat in bacterial spores?

It holds proteins and prevents water permeability.

What protective features do bacterial spores have?

The outer membrane protects against UV light, the cortex maintains specific water content, and the inner membrane protects core contents.

What types of reproduction do fungal spores undergo?

Fungal spores can undergo asexual and sexual reproduction.

What are ascospores and which fungi produce them?

Ascospores are sexual spores produced by fungi such as Ascomycota, Saccharomyces, and Kluyveromyces.

What are some examples of structures produced by mold spores?

Examples include conidia (Aspergillus, Penicillium) and sporangiospores (Mucor, Rhizopus).

What is the primary mycotoxin of concern in the U.S.?

Aflatoxins are the primary mycotoxin of concern.

Which fungi produce aflatoxins?

Aflatoxins are produced by Aspergillus flavus and Aspergillus parasiticus.

What are the acute effects of aflatoxins on health?

Acute effects include liver damage, edema, altered digestion, and death.

What are the chronic effects of aflatoxins?

Chronic effects include impaired food conversion, slower growth, and cancer.

What is the most toxic form of aflatoxin?

AFB1-8,9-epoxide is the most toxic form.

What is vomitoxin and which fungus produces it?

Vomitoxin is a mycotoxin produced by Fusarium spp.

What are tremorgens and which fungus is associated with them?

Tremorgens are mycotoxins associated with Penicillium species.

What are the two main categories of foodborne diseases?

Infection and intoxication.

What is the difference between invasive and non-invasive foodborne infections?

Invasive infections involve the colonization of cells, while non-invasive infections do not.

Name two examples of invasive foodborne pathogens.

Listeria monocytogenes and Shigella.

What type of toxin is responsible for true food poisoning?

A preformed toxin.

Which bacteria are known to produce preformed toxins?

Clostridium botulinum, Staphylococcus aureus, and Bacillus cereus (emetic).

What is a key characteristic of bacterial endospores?

They are a survival structure formed by some Gram-positive bacteria.

What are the two categories of spores?

Endospores and exospores.

What triggers the germination of bacterial endospores?

Conditions that allow spores to exit dormancy, which may be good or just sublethal.

What are the components of a bacterial endospore?

Exosporium, spore coat, cortex, and core.

How do bacterial endospores resist extreme conditions?

They are resistant to extreme temperatures, acid, desiccation, and antimicrobials.

What is the role of dipicolinic acid (DPA) in bacterial endospores?

It helps maintain the dehydrated core and contributes to resistance.

What is the D-value in thermal processing?

The time required to reduce the microbial population by 1 log at a set temperature.

What is the impact of sporeformers on food safety?

They pose challenges for food processors and consumers due to their resistance and potential for spoilage.

What is the main goal of vegetative cells compared to spores?

Vegetative cells focus on replication and metabolism, while spores focus on survival.

How does gamma radiation affect bacterial spores?

Decreased water content in spores confers protection against gamma radiation.

What is the significance of SASP in bacterial spores?

SASP protects DNA and helps spores resist UV radiation.

What are some methods to prevent the outgrowth of spores?

Thermal processing and canning methods that achieve a 12-log reduction.

What types of disease characteristics are associated with Gram-positive foodborne pathogens?

They range from gastrointestinal distress to paralysis and include invasive infections, infections, intoxications, and toxicoinfections.

Which Gram-positive microorganisms are known to form spores?

Bacillus and Clostridium.

What are the two categories of Gram-positive foodborne pathogens based on spore formation?

Sporeformers (e.g., Bacillus, Clostridium) and nonsporeformers (e.g., Staphylococcus, Listeria).

What is the infectious dose characteristic of many Gram-positive pathogens?

Many have higher infectious doses compared to some Gram-negative pathogens.

What are the main Gram-positive foodborne pathogens mentioned?

Mycobacterium, Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, Clostridium perfringens, and Listeria monocytogenes.

What gram positive pathogen causes the greatest number of illnesses in the United States per year?

clostridium perfringens

what gram-positive pathogen causes the hospitalizations and deaths annually in the United States?

Listeria monocytogenes

what gram-negative bacteria causes the most illnesses per year in the united states

Campylobacter (salmonella is close)

what gram-negative bacteria causes the most hospitalizations and deaths in the United States per year

Salmonella

What is the main reservoir for Staphylococcus aureus?

Humans, particularly in the nasal passages, skin, hair, cuts, and wounds.

What are the symptoms of Staphylococcus aureus intoxication?

Symptoms include vomiting, nausea, cramps, diarrhea, and headache.

What types of foods are commonly associated with Staphylococcus aureus outbreaks?

Protein-rich foods that are subject to handling and temperature abuse.

What is the onset time for the emetic toxin (cereulide) produced by Bacillus cereus?

Onset is between 0.5 to 5 hours.

What is the optimal growth temperature for Clostridium botulinum Group I strains?

37°C.

What environmental sources are associated with Clostridium botulinum contamination?

Water, sediment, and various soil types worldwide.

What is the primary prevention strategy for Bacillus cereus outbreaks?

Good manufacturing practices (GMPs) and proper storage to prevent temperature abuse.

What is the infectious dose for the diarrheal enterotoxin produced by Bacillus cereus?

Greater than 10^4 CFU/g.

What is a significant characteristic of the emetic toxin produced by Bacillus cereus?

It is resistant to heat, pH, and proteolysis.

What is the duration of symptoms caused by the emetic toxin from Bacillus cereus?

12 to 24 hours.

What are the conditions that inhibit the growth of group 1 Clostridium botulinum?

pH < 4.6, NaCl > 10%, and aw < 0.94.

What is the main pathogenicity mechanism of Staphylococcus aureus?

Intoxication due to heat-stable enterotoxin production.

What is the typical duration of symptoms for Staphylococcus aureus intoxication?

24 to 48 hours.

What are the two main types of toxins produced by Bacillus cereus?

Diarrheal enterotoxin and emetic toxin (cereulide).

What type of microorganism is Bacillus cereus in terms of oxygen requirements?

It is aerobic or facultative anaerobic. Only produces toxin under aerobic conditions

What is a significant source of contamination for Clostridium perfringens?

Improperly stored cooked meats and gravies.

What is the potency of the toxin produced by Clostridium botulinum?

Extremely potent toxin with an LD of 1 µg.

What are the components of the botulinum toxin?

Heavy chain and light chain.

How does the botulinum toxin affect muscle contraction?

The cleaved light chain interacts with SNAP 25, preventing muscle contraction.

What is the onset time for botulism symptoms?

12-36 hours after exposure.

What are common symptoms of botulism?

Nausea, vomiting, dry mouth, fatigue, dizziness, headache, flaccid paralysis, and vision problems.

What foods are commonly associated with botulism outbreaks?

Fermented foods, canned foods, temperature-abused foods, and honey (infant botulism).

What is the prevention method for botulism in foods?

Use of nitrite in smoked or cured meats and high thermal inactivation processes.

What is the doubling time for Clostridium perfringens at optimal temperatures?

As low as 7 minutes at 43-45°C.

What type of infection does Clostridium perfringens cause?

Toxicoinfection through enterotoxin (CPE) produced in the GI tract.

What are the symptoms of Clostridium perfringens infection?

Explosive diarrhea with a distinct odor and abdominal cramps.

What is the onset time for symptoms of Clostridium perfringens infection?

8-16 hours after exposure.

What is the growth temperature range for Listeria monocytogenes?

0-45°C.

What are the symptoms of listeriosis?

Flu-like symptoms, GI distress, high mortality (~16%), and complications such as septicemia and meningitis.

What are the virulence factors of Listeria monocytogenes?

InlA and B internalin surface molecules, Listeriolysin O (LLO) active in acidic enviornments to destroy phagosome, Plc phospholipases aid in vacuole escape, and ActA actin motility.

What is the significance of zero tolerance for Listeria in food safety?

No detectable presence in 25 g samples is required for safety.

What type of products are associated with Mycobacterium bovis outbreaks?

Raw, unpasteurized dairy products.

What is the primary prevention method for Mycobacterium bovis infections?

Pasteurization of dairy products.

What is the primary mode of transmission for Listeria monocytogenes?

Invasive infection that uses actin polymerization to invade neighboring cells.

What are the high-risk groups for listeriosis?

Pregnant women, newborns, and immunocompromised individuals.

What is the role of environmental conditions in Clostridium perfringens outbreaks?

Temperature abuse and undercooked high-protein foods contribute to outbreaks.

What is the treatment for botulism?

Removal of the toxin and possibly ventilation support.

What is the significance of the cpe gene in Clostridium perfringens?

It is responsible for the production of the enterotoxin that causes illness.

What are the characteristics of Listeria monocytogenes?

Psychrotroph, facultative anaerobe, non-sporeforming, and has peritrichous flagella.

What is the duration of Clostridium perfringens symptoms?

12-24 hours, typically self-limiting.

What are Enterobacteriaceae?

A family of Gram-negative, facultative anaerobic rods commonly referred to as enterics.

What are coliforms?

Non-sporeforming, Gram-negative rods that ferment lactose at 35-37°C and are associated with the GI tract of warm-blooded animals.

How can coliforms be used in food safety?

They serve as indicator organisms for potential fecal contamination and cleanliness of food.

What types of infections can Gram-negative microorganisms cause?

Infections can be invasive or non-invasive, and can also lead to toxicoinfections and immune responses.

List some common gram-negative pathogens.

Shigella spp., Yersinia spp., Brucella spp., Vibrio spp., Escherichia coli, Salmonella enterica, and Campylobacter spp.

What is the primary serotype of Enterohemorrhagic E. coli (EHEC)?

O157:H7, also big six (O26, O45, O103, O111, O121, O145) also known as Shiga toxin-producing E. coli.

What is the significance of Shiga toxin produced by EHEC?

It is cytotoxic and can severely damage the intestinal lining, leading to serious health complications.

What are the common sources of E. coli O157:H7?

Common sources include raw or undercooked ground beef, fresh produce, unpasteurized milk, and water, petting zoos, childcare.

What is the infectious dose for EHEC Enterohemorrhagic E. Coli?

As low as 10-100 cells.

What are some symptoms of Hemolytic Uremic Syndrome (HUS)?

Symptoms include renal failure, hemolytic anemia, and can lead to complete loss of kidney function.

What is Enterotoxigenic E. coli (ETEC) known for?

Causing diarrhea in infants and travelers, typically not serious but can lead to watery diarrhea. Produces enterotoxin causing toxicoinfection. Colonizes in small intestine using fimbriae

What are the characteristics of Diffuse-adhering E. coli (DAEC)?

Associated with infant diarrhea and can be bloody but typically mild. Does not invade cells, adherence to HEp-2 and HeLa cell lines

what characterizes Enteroaggregative Ecoli (EAEC)

causes persistent diarrhea in children/infants Ex includes O104, O111 (O111 in big six), Aggregative adherence to HEp-2 cells, appearance of stacked bricks, second most common form of traveler's diarrhea

What are the symptoms of Enteropathogenic E. coli (EPEC)?

Causes watery diarrhea, and is severe for infants. Infects human epithelial cells (Hep2 cell lines), mostly associated with developing countries

What characterizes Enteroinvasive E. coli (EIEC)?

It causes non-bloody diarrhea and dysentery, by invading epithelial cells and escape phagosome. Humans normal reservoir

What is the role of fimbriae in pathogenic E. coli?

Fimbriae aid in the adherence of bacteria to the intestinal lining, facilitating infection.