Microbiology Exam 3
Staphylococcal ___________________ are relatively heat-stable, so they maintain pathogenicity in warm food and are even stable to stomach acidity.
enterotoxins
Acidic foods generally need a higher canning temperature than do nonacidic foods.
false
Waterborne illness only occurs from exposure to contaminated drinking water, not from recreational use of contaminated water.
false
Coliforms in a water sample indicate ________ contamination.
fecal
Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
fever
Factors that enhance an organism's ability to adhere to host tissues include __________.
fimbriae
Which of the following features of Salmonella prevent it from being phagocytosed?
flagella
In the developed countries of the world, most intestinal infections are transmitted via
food
What organisms are the most likely pathogens to grow in food that has low water activity or solute-loaded?
fungi
Staphylococcus aureus is a particularly dangerous organism when in food due to the enterotoxins some species produce. These toxins are dangerous because they are __________.
heat-stable, acid-tolerant superantigen toxins
Which organisms are NOT involved in food fermentations?
sulfuric acid bacteria
A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)
superantigen.
Measles viruses are capable of inactivating host defenses by
suppressing the immune system
The collective term for the organisms living on or in the human body, as opposed to a general term for organisms in an environmental habitat, is
the human microbiome
Receptors on the surface of pathogens that are made of glycoproteins and lipoproteins are called
septicemia
The spread of pathogens through the blood and lymph systems that results in a bloodborne systemic infection is called
septicemia.
The rhizosphere is the
soil that receives secretions from plant roots.
In the ocean, ________ are present in the highest numbers.
viruses
The most important potential common source of infectious disease is
water
What trait distinguishes semiperishable foods such as potatoes and nuts from perishable foods such as meats?
water activity/moisture content
Pickling is a type of food preservation utilizing
weak acids
Which of the following statements describes the most likely reason for supplementing antibiotic therapy?
Antibiotic therapy addresses only the growth; it doesn't address the extreme dehydration
Which domain of the A-B toxin binds to cell surface receptors on the host cell?
B domain
Bacteria make up about ________ the weight of fecal matter.
1/3
Which of the following best explains why the pressure cooker is so important in the canning process?
A pressure cooker utilizes steam to create a higher-pressure environment that allows the food to cook at higher temperatures than normal. The higher temperatures kill most contaminating microbes and endospores and therefore effectively sterilize the food.
Why are antibiotics often ineffective in treating food poisoning (food intoxication)?
Antibiotics target bacteria; they do not damage toxins.
Which group of microbes is most abundant in the Gastrointestinal tract?
Bacteriodetes
How can capsules enable bacteria to evade the immune system?
Capsules block the complement biding sites on the surface of the pathogen.
When an individual has severe diarrhea, as can occur with cholera, rehydration solution with glucose, salt, sodium bicarbonate, and potassium chloride can be administered. Why is it important to use a solution like this rather than simply giving the individual water?
Diarrhea causes the loss of electrolytes, not just fluids. It is important to replace the electrolytes as well as the water.
Which U.S. government agency monitors water utility reports?
Environmental Protection Agency
Which of the following are properties of exotoxins?
Exotoxins target specific cellular structures or molecules. Exotoxins are protein molecules. Very small amounts of exotoxin can be lethal.
Food that is heavily salted or candied does not need to be refrigerated. Why not?
Extremely concentrated solutions are very hypertonic and therefore desiccate microorganisms. As a result, there is no need for lower temperatures through refrigeration to slow growth.
Microbes capable of fermentation are often used in food. What is the main function of fermentation for the microbes?
Fermentation regenerates NAD+ so that glycolysis can continue.
Which of the following enzymes breaks down the "glue" that holds cells together?
Hyaluronidase
Tests to monitor water safety often report the number of fecal coliform bacteria found in samples. Which of the following statements accurately reflects water safety recommendations based upon fecal coliform levels?
If the level of fecal coliform bacteria is low, the likelihood of fecal contamination is low, but the water may still be unsafe because of the presence of other pathogens.
________ is the growth of microorganisms NOT normally present within a host.
Infection
Which of the following are requirements for causing disease within a host?
adherence to host tissues gaining access to the host via a portal of entry evasion of host defenses
Where do Salmonella pathogens grow and replicate in the infected host?
Inside phagocytes
How does the protozoan Trypanosoma evade detection by the immune system?
It can change the surface antigens frequently, preventing the immune system from tracking it.
Why is a release of endotoxin into the bloodstream potentially deadly?
It can lower blood pressure and cause the patient to go into shock.
________ in saliva cleaves glycosidic linkages in the peptidoglycan that is present in bacterial cell walls, weakening the wall and potentially causing cell lysis.
Lysozyme
Where is the site of Shigella attachment in the host?
M cells
Which of the following bacterial pathogens is found in aquatic environments and is commonly present in air conditioning systems?
Legionella pneumophila
Endotoxins are also known as
Lipid A
Filopods harboring ________ are especially dangerous because the pathogens move about host tissues, even infecting the central nervous system, without being exposed to the immune system.
Listeria monocytogenes
What are leukocidins?
Molecules that are capable of destroying phagocytes
Meningitis and gonorrhea are caused by
Neisseria species
Compared with an endotoxin, would a bacterial exotoxin generally be more likely to function after it had been significantly heated?
No, because exotoxins are heat-labile and less resistant to heating than endotoxins.
What is the MOST abundant prokaryote (non-phototroph) in the ocean?
Prochlorococcus
Which group of bacteria are most abundant on Skin?
Propionibacterium
What is the etiologic agent of typhoid?
Salmonella
Salmonellosis is most frequently caused by
Salmonella enterica serovars Typhimurium and Enteriditis.
Which of the following virulence factors would be found in Staphylococcus aureus?
Staphylokinase
How are superantigens different from other types of exotoxins?
Superantigens cause an overstimulation of the host immune system.
How does a capsule help certain bacteria evade detection by the immune system?
The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.
How do fibrinolysins enhance a pathogen's virulence?
They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.
How are immune cells able to detect foreign pathogens?
They are able to detect structures on the surfaces of foreign cells that are not found in the host.
How do Shigella cells move between host cells?
They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.
How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?
They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.
A researcher wanted to determine the LD50 (lethal dose that kills 50% of the infected hosts) for a newly isolated bacterial pathogen. Mice were inoculated with diluted cultures containing between 101 and 107 cells. After two days, all of the mice had died EXCEPT for the uninoculated controls. Which of the following is the most likely explanation?
This pathogen is highly virulent in mice.
Reheating food to a temperature sufficient to kill bacteria is helpful in making food safer. However, is there a way that one can get food poisoning despite food having been reheated?
Toxins may be heat-stable above temperatures that kill bacteria.
True or False: If a person consumes food containing pathogens that have NOT yet produced toxins, the person is consideredto have a food infection but NOT food poisoning.
True
Which of the following microorganisms actually grows inside the macrophage?
Tuberculosis bacterium
When would endotoxins be released from a bacterial cell?
When the cell dies
An endogenous pyrogen is
a chemical produced by a host's own immune system that causes fever
A pathogen must __________ in order for it to cause disease.
attach and multiply
The decrease or loss of virulence of a pathogen is referred to as
attenuation.
An outer coat consisting of a dense, well-defined polymer layer surrounding a cell and used in attachment is called a
capsule
The degree of susceptibility a food has to microbial activity is determined by its
chemical characteristics, physical characteristics, and water content.
Gram-negative, rod-shaped bacteria that are facultative anaerobes, are non-spore formers, and ferment lactose to acid and gas are __________.
coliforms
Clostridium perfringens causes gas gangrene, a serious infection of the muscle tissues that can lead to amputation. Clostridium are Gram-positive endospore-formers and obligate anaerobes that are killed when exposed to oxygen. Which of the following virulence factors would be most helpful to this organism in establishing an infection?
collagenase, an enzyme that destroys collagen, which is a major protein of connective tissues
The most common route of transmission of Salmonella enterica typhi worldwide is through
contaminated water
Legionella pneumophila is generally transmitted by
contaminated water in coolers, pools, and domestic water systems.
An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
cytotoxin.
Severe cases of Staphylococcus aureus food poisoning may require treatment for
dehydration
Streptokinase works to ________ fibrin clots while coagulase works to ________ fibrin clots.
dissolve / promote
Staphylococcus aureus is a common causative agent of foodborne disease because it
grows on many foods, is present in some humans that work in food processing, and produces several heat-stable enterotoxins.
Which of the following is an important factor in the development of dental caries?
high sugar diet
What factors could contribute to differences in the skin microbiome of individuals?
hygiene inflammatory diseases sex occupation geography age moisture level NOT DIET
The presence of specific ________ signals that a given water source might be contaminated with pathogens.
indicator microorganisms
Adherence factors include ALL of the following EXCEPT
lipopolysaccharide layers.
Which of the following is NOT important for the adherence of bacteria to host tissues?
lipopolysaccharides
The biological oxygen demand (BOD) is a metric to indicate the capacity of
microbes to oxidize organic compounds.
A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
neurotoxin.
The pH of most foods is
neutral or acidic
Irradiation of food uses
non-ionizing radiation.
The most common source of individual foodborne botulism outbreaks are due to consumption of
nonacid, home-canned vegetables.
Flour and sugar are classified as ________ foods.
nonperishable
The majority of foodborne infections in the United States and Cruise Ships are NOT caused by a bacterial pathogen but instead are caused by ________, which is nicknamed "the 24-hour bug."
norovirus
Nearly 90% of all foodborne illnesses are associated with __________.
norovirus, Salmonella, Clostridium perfringens, and Campylobacter jejuni
Microbes that dominate environments where organic matter is extremely low (limited) are called what?
oligotrophs
The best term to describe the general process by which microorganisms cause diseases is known as
pathogenesis.
Clostridium perfringens food poisoning leads to diarrhea, because the
permeability of the intestinal epithelium is altered by the toxin it produces.
The process by which white blood cells ingest and kill bacteria is called
phagocytosis
Exotoxins are ________, but endotoxins are ________.
proteins / lipopolysaccharide-lipoprotein complexes
The principle behind salt or sugar preservation is to
reduce water activity (aw).
Psychrotolerant microorganisms can survive and grow at
refrigeration temperatures.
The rate of contaminant microbial growth during the exponential phase in food depends on
temperature, nutrient value, and water content.
Certain traits that allow pathogens to create infection and cause disease are termed
virulence factors.
Food poisoning generally results from the ingestion of food containing microbial toxins.
true
Norovirus is commonly transmitted by the fecal-oral route.
true
The critical step in making water safe to drink is chlorination.
true
