Old Exam Questions Flashcards
LAB are predominantly which genus?
Lactobacillus spp.
True or False. Lower the pH, higher energy is required by cell to maintain cell intracellular pH neutrality and less energy is left for the growth.
True
How many hours does milk need to cool down to 4 - 7 C?
2 hours
Which pathogen dominates in fish and shellfish?
Vibrio
True or False. Lactic acid bacteria are always a good and positive bacteria to have in your dairy products?
False.
Most common minimum Aw for mold
0.8
Which will require the highest “intervention” dose for inactivation?
Clostridium spore
What does VBNC stand for?
Viable but not culturable
What does temperature regulate?
The growth of bacteria
The lipid content of the cell membrane
Gene expression of bacteria
Explain the how and why ground meat products are more correlated to increases in outbreaks.
Ground meat products are correlated to increase outbreaks given the composition of low quality meat and improper cooking/handling.
What bacteria are apart of the spoilage of fish and shellfish products
Pseudomonas
Vibrio
Morganella spp.
True or False. Common microorganisms and foodborne pathogens that are present on food (e.g., beef) surfaces show seasonal variation
True
Coliforms ferment lactose to produce?
CO2
At what stage would bacteria produce their byproducts (toxins, enzymes, etc)
Late log phase
True or False. Do microorganisms need both processes of adapting to acid protection in order to survive?
True
What is the most common minimum Aw for yeast?
0.80
Mold is able to survive low Aw because?
Compatible solutes
Psychotropic bacteria that cause sweet curdling do so by attacking?
Casein
Stickiness on meat starts at what CFU?
10^8 CFU/cm^2
What is the most important bacterial foodborne pathogen that can multiply in raw milk stored at low temperatures and can cause foodborne outbreaks?
Listeria monocytogenes
Food spoilage includes
Reduction of the texture of food
It can be harmful to the consumer
Reduction of the nutritional value of food
Reduction of the flavor of food
What is biofilm?
Aggregation of bacteria living together on a solid surface.
True or False.The minimum Aw of bacteria, mold, and yeast to grow is the same as the minimum Aw for them to produce toxins.
False
Minimum water activity needed for the growth of gram-negative and gram-positive bacteria.
0.97: 0.9, respectively
What is one of the main specific issues with leaving fish for too long at improper temperature conditions?
Histamines
What is infection and intoxication?
Ingestion of organism grow, replicate, colonize, and potentially release toxins in the host’s intestine; Ingestion of bacteria that was growing on food and releasing toxins, respectively
What is the purpose of pasteurization?
Reduce microbial load and enzyme activity
pH levels of meat from a well rested animal is
5.4-5.6
The Most important psychrotrophic bacteria in milk that can multiply at low temperatures and can result in milk spoilage
Pseudomonas
The application of two or more hurdles to control the growth of foodborne pathogens facilitates
- It can be more effective than one intervention treatment
- Facilitates application of milder intervention treatment
- Helps retain organoleptic properties of food after intervention
Proteolysis produce?
Bitter, putrid flavor and coagulation
Major agents of dairy spoilage?
LAB
Coliforms
Psychotropic bacteria
Which milk protein is more susceptible to the susceptible microbial proteolysis?
Casein
A main byproduct of spoilage bacteria on fish is an enzyme. What is the main issue with these bacteria and enzyme?
Even if the bacteria is killed the enzyme can still be active
True or False. At low cellular pH, cells have to spend more energy to maintain neutrality and less energy is left for their growth.
True
Common source of spoilage bacteria in meat products is
Hide, hooves, feathers
Sources of contamination of raw milk
Soil, skin tissue, water quality and utensils
Sweet Curding is predominately caused by which genus?
Bacillus spp.
Lipolysis produce?
Rancid and fruit flavors
True or False. Biofilms are more difficult to get rid of compare to bacteria.
True
What methods of growth are most likely to be related to Psychrotropic Bacteria?
Proteases and lipases
What is NOT an intrinsic factor? water activity, temp, naturally occurring compounds, pH, nutrients
Temp
What is the primary energy source found in milk?
Lactose
Why is milk a good growth media?
neutral pH, sugar, high water content, protein, fat
At neutral pH which will response/mechanism will be turned on?
Homeostatic response
Modified Atmosphere Packaging (MAP) works by increasing the concentration of
CO2
What is the source of microorganisms in beef?
Hair
hooves
hide
GI Tract
What are the USDA and FDA responsible, respectively?
Meat and poultry and all other food products, respectively
What is the purpose of the FoodNet?
Designed to monitor each of the events that occur along the foodborne diseases
True or False. Aerobic and anaerobic pathways are both high energy productions
True
Why does the Emetic toxin (Cereulide) have such a fast onset for illness?
The toxin is an amino acid synthetase
True or False. Only coagulase-positive Staphylococcus aureus strains are pathogenic
False
Bacillus is a….
Gram-positive, spore-forming, rod-shaped
Diarrheal Food Poisoning and Emetic Food Poisoning by B. cereus are commonly from which sources?
Fish and meats; Starchy food (rice), respectively
What is the most distinct symptom of Emetic syndrome associated with a cereulide -producing Bacillus strain?
Vomiting
Fermentation of vegetable is a way of preserving food and its nutritive values. Which microorganism they use also depends on their culture. What are they?
America/Europe: LAB and Yeast
Asia: Mold
What are Indicator Organisms used to assess?
Food safety and food quality
Extracellular protease acts on casein molecules resulting in free amino acids and peptides. What are they used for or cause?
1) Required for the growth of many LABs
2) Flavor development during ripening process of cheese
3) Generation of either bitter peptides or non-bitter peptides
Heterofermentation are responsible for?
Aroma and flavor
Emetic Food Poisoning is caused by
Cereulide
Which Bacillus species has the ability to grow in the cold (below 7C)?
Bacillus weihenstephanensis
What are some of the reasons that we ferment foods?
We ferment foods due to climate, food preservation, digestibility of grains and flavor/aroma.
Which fermentation pathway is the most efficient and common?
Embden-Meyerhof-Parnas
What are Index organism and Indicator organism?
Microorganism or group of microorganisms that is indicative of a specific pathogen; Microorganism or group of microorganisms that are indicative that a food has been exposed to conditions that pose an increased risk, but not necessarily pathogenic, respectively
Sugar is converted to what product(s) during fermentation?
CO2
Acetic acid
Lactic Acid
Ethanol
Homofermentation are responsible for?
Acid production
What is mandatory criteria?
A limit which may not be exceeded. If exceeded food need to destroyed, reprocessed, diverted.
Staphylococcal toxin
Highly resistant to proteolytic enzymes
Heat-stable
Common reservoir of S. aureus?
Hair, nose, respiratory droplets, skin
Which factors determine which pathway organism uses
Oxygen conditions
Availability of sugar e.g. pentoses, hexoses
Genetic make up
Membrane proteins
True or False. B. cereus outbreaks are highly underestimated.
True
Microbiological Criteria represent a level of microorganism above which action is required. Below mentioned are a few examples. Select the most relevant example for Microbiological criteria.
Listeria number is 10 CFU/g in cheese; we need to take action
Microbiological Criteria are focused on
Bacterial metabolite, bacteria toxin, fecal coliforms, presence of bacteria
Who has the ability to issue recalls?
FDA
What is the biological process of fermentation?
The production of byproducts (vinegar, antibodies, citric acid, etc) in the presence or absence of oxygen.
Which will have the shortest incubation period?
Bacillus strain with emetic toxin
B. Cereus and their spores are?
1) Spores survive the pasteurization
2) It is important in foodborne illness: cells are resistant to treatment and can grow at lower temperature.
3) Spore more hydrophobic than the vegetative cells and repel sanitizers allowing them to survive on surfaces
Which one of the following does not have GRAS status?
Salmonella
Microbiological criteria consist of:
1)toxins and metabolites
2) sampling plan
3) analytical methods used for identification
4) The organism of concern
Complete oxidation and fermentation of glucose generates
34 ATP and 1 to 2 ATP, respectively
True or False. Homo and hetero fermentative strains are usually mixed in a fixed ratio to generate a flavor profile in a fermented product
True
A mandatory criterion is established when
No other effective tool/intervention method is available
What is the common source of non-starter lactic acid bacteria (NSLAB) in cheese?
Surrounding where cheese is aged
Staphylococcal-associated gastric distress is classified as
Food intoxication
Entner doudoroff pathway is important for fermented dairy products as it allows the use of __________ disaccharide. The ED pathway enables the bacteria to use ______ sugar which is mostly excreted by other bacteria.
Lactose and galactose
Most staphylococcal food poisoning is traced to food contaminated
By humans during preparation
True or False. The variable sampling plan is used for when the target microorganism is uniformly distributed
True
Which one is a heterofermentative microorganism?
Propionibacterium
S. aureus is bacteria that is responsible for?
Staphylococcal food poisoning, an intoxication, which is caused by a heat stable toxin
Who Established Microbiological Criteria?
FAO
NACMCF
NAS
ICMSF
True or False. Fermentation can be used for the detoxification of foods
True
Fecal coliforms are
of animal origins
contain both pathogen and nonpathogenic bacteria
Clostridium is divided into Groups I, II, III, and IV based on the physiological difference. Which of these four physiological groups causes concern and is involved in human infection?
Group I and II
True or False. You can neutralize the botulinum toxin by boiling for 10 minutes
True
During a Salmonella outbreak investigation, which of the following foods would you prioritize for sampling if interviews reveal it was frequently consumed by those infected.
Fresh lettuce salads
True or False. Listeria strains love growing in moist areas.
True
Listeriosis is a ________
infection
What is the most common form of Clostridium infection in humans?
infant botulism
Which one the following can survive in the acidic environments (pH: 4.2)
E. coli O157
Botulinum Neurotoxin
The Actin “Rocket“ (ActA Protein) that is found in some pathogens are used for?
Hijacks the host’s actin filaments, pushing itself around the host cell and into neighboring cells
What are the reasoning for listeria high cause of death
1) Widely distributed in nature
2) Grows inside human phagocytes
3) 13-30% mortality rate
4) Long lag time
Listeria monocytogenes targets what in the body
liver and spleen
Shigella has
1) very low infective dose
2) spread through person-to-person contact
3) Very low infective dose and highly contagious
Which is the most common Shigella species in the United States?
Shigella sonnei
EHEC mainly targets what in the body?
kidney
The Top 7 serogroups for the EHEC are
O121
O45
O26
O145
O111
O103
O157
The most important feature of Listeria which facilitates its occurrence in a food processing facility.
Availability of moisture and cold temperature
Salmonella produce_________ colored colonies on XLD and HE agar plates
Black
Which category of food is most commonly associated with Clostridium botulinum outbreaks?
Home-canned
In a foodborne outbreak investigation, which method is commonly used to confirm the link between a suspected food and the illnesses
Performing genetic fingerprinting on pathogen strains from patients and food samples
Clostridium botulinum results in _______________
intoxication
Name a food product that in the past has been associated with the Listeria monocytogenes outbreak.
mexican-style cheese
What are the virulence factors of EHEC?
Shiga toxin
Intimin
Clostridium botulinum is a
1) spore former
2) gram positive
3) obligate anaerobe
4) rod
Clostridium strains infecting humans does not grow and germinate below
pH 4.6
The O-antigen is located on
LPS on the external surface of the bacterial membrane
Isolation of Clostridium botulinum use of
1) Heat treatment of the sample
2) Anaerobic incubator
3) Cooked meat media
In the case of a Listeria outbreak in a food production facility, which of the following conditions would most likely contribute to persistent contamination?
Moist environments and equipment that are hard to clean
Why does the isolation of Clostridium require heat treatment of samples at 60-80°C for 10 minutes?
Kills the vegetative cells and spores survives
pH value below which Clostridium botulinum does not grow?
4.6
Which is the most commonly used food preservative for controlling the Clostridium botulinum in food products?
Nitrate
What are some facts of Listeria?
1) Poor competitor under room temperature
2) Outcompete others in refrigerated conditions
3) Can lead to miscarriage
4) Correlated with ready to eat foods
What is a “12D thermal process”?
achieve a 12-log reduction
Which of the following symptoms is most characteristic of botulism caused by Clostridium botulinum?
Blurred vision and difficulty swallowing
What is the incubation period of Listeria?
1-4 weeks
What is the virulence characteristics of Enteroaggregative Escherichia coli (EAEC)?
1) Persistent diarrhea
2) Stacked brick-like appearance on the cell
3) EAEC adheres to the intestinal mucosa
The most common animal reservoir of EHEC is
Cattle
What is the primary reason for conducting environmental sampling in a food processing facility during an outbreak investigation?
To identify potential sources and points of contamination
The presence of five different outbreak-associated strains at a site indicates
Long term presence
Enteroinvasive Escherichia coli (EIEC) is biochemically, genetically, and pathogenetically closely related to
Shigella
True or False. In the U.S., there is a zero-tolerance policy for Listeria monocytogenes in ready-to-eat foods.
True
Which of the following conditions best promotes the growth and toxin production of Clostridium botulinum in food?
Low oxygen and low acidity
Salmonellosis ranges clinically from the
1) enteric fevers
2) common gastroenteritis
What is the primary toxic target of aflatoxins produced by mold species?
Hepatotoxicity
Which mycotoxins can be passed through the milk of the animal?
Aflatoxin M1 and M2
True or False. Mycotoxins (Aflatoxins, Ochratoxins, Patulin, Citrinin) are heat-stable toxins.
True
What are key prevention strategies for Vibrio cholerae transmission?
1) Chlorination of drinking water
2) Cooking seafood thoroughly
3) Proper sanitation and hygiene practices
What is the most common symptom of Vibrio cholerae infection?
Profuse rice-watery diarrhea
Which of the following is a significant post-infection complication of Campylobacter jejuni?
GBS
What are the health impacts of ochratoxin A contamination in food?
Nephrotoxicity
Carcinogenicity
Immune suppression
What are the main conditions favoring mold growth?
Moderate temperatures
High humidity
Which factors contribute to the survival of Vibrio species in the environment?
1) Presence in molluscan shellfish
2) Estuarine water conditions
Which pH level is most suitable for mold growth?
2.0-4.5
Which of the following foods is a common source of Vibrio infections?
Raw shellfish
Which Vibrio species is associated with severe tissue necrosis and high mortality in septicemia cases?
Vibrio vulnificus
Which symptom is most characteristic of Campylobacter infection?
Bloody diarrhea
What is the main environmental factor that limits the survival of Campylobacter outside a host?
High oxygen levels
Which species of Campylobacter are most commonly associated with foodborne outbreaks?
Campylobacter coli
Campylobacter jejuni
There are 200 serogroups of Vibrio cholerae, but how many of those serogroups produce the toxins?
2
True or False. Vibrio infection CAN be controlled through shellfish sanitation program.
False
True or False. Up to 100% of poultry that makes it to the retail could be contaminated with Campylobacter
True
What are signs of food spoilage from molds?
Slimy or mushy textures
Discoloration
Off-flavors and musty odors
Fuzzy growth
Which virulence factors are associated with Vibrio parahaemolyticus?
TDH
What is the primary benefit of using PCR over traditional culture methods for microbial detection?
It is faster and highly specific
True or False. A blood stream infection by V. vulnificus has a high mortality rate (50%)
True
True or False. Vibrio toxins are heat-stable.
False
Which mold-produced toxin is a leading cause of liver cancer in areas with high dietary exposure?
Aflatoxin B1
Which mycotoxins are associated with Nephrotoxicity?
Citrinin and Ochractoxins
Which fungal genus is not associated with pathogenic mycotoxin production?
cladosporium
Which enzyme activity is most likely to increase during fungal spoilage of fruits?
Pectinase activity
Which detection method offers high specificity by amplifying microbial DNA?
PCR (Polymerase Chain Reaction)
What are the virulence factors of Campylobacter jejuni?
Enterotoxin production
Which genus is most associated with food spoilage under refrigeration?
Cladosporium
Which of the following describe ochratoxin A’s mechanism of toxicity?
Disrupting mitochondrial function
Binding serum albumin
Inducing oxidative stress
Which enzymes are involved in food spoilage by molds?
Amylases
Cellulases
Proteases
What are the advantages of immunomagnetic separation (IMS)?
1) Concentration of target bacteria
2) Removal of non-specific targets
What are the primary symptoms of acute aflatoxicosis?
Jaundice
Abdominal pain
Nausea and vomiting
Which detection method is the fastest but requires a calibrated microscope?
DMC
Which toxin produced by Vibrio cholerae is responsible for causing watery diarrhea?
Cholera toxin (CT)
Cholera is an intestinal infection associated with:
1) Natural and man-made disasters
2) Overcrowding
3) Contamination of food during or after its preparation
4) Improper elimination of human waste
Which symptoms are commonly associated with Vibrio vulnificus infections?
Skin lesions
Septicemia
Wound infections
Which condition is ideal for Campylobacter growth?
Microaerophilic conditions and temperatures around 42°C
What is the primary virulence mechanism of Vibrio cholerae that leads to dehydration?
Activation of adenylate cyclase by cholera toxin
What is a typical outcome from long term exposure of consuming food contaminated with mycotoxins?
Cancer
Which of the following is the primary risk associated with molds contaminating animal feed?
Introduction of mycotoxins into the food chain
Which prevention strategies are recommended to reduce Vibrio infections from seafood?
1) Cooking shellfish thoroughly
2) Avoiding raw oysters during warm months
Which of the following are common risk factors for mold growth on food?
Storage in warm, humid conditions
Inadequate drying before storage
High water activity
Which species of Vibrio are most commonly associated with foodborne illness?
Vibrio parahaemolyticus
Vibrio cholerae
Vibrio vulnificus
