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Microbiology Exam 2
Terms in this set (131)
Endotoxins are also known as
When would endotoxins be released from a bacterial cell?
When the cell dies
Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
Why is a release of endotoxin into the bloodstream potentially deadly?
It can lower blood pressure and cause the patient to go into shock.
An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
Which domain of the A-B toxin binds to cell surface receptors on the host cell?
How are superantigens different from other types of exotoxins?
Superantigens cause an overstimulation of the host immune system.
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)
A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
Escherichia coli living in the human large intestine is known to produce vitamin K and B-complex vitamins in exchange for a nutrient-rich habitat. This host-microbe interaction is an example of
Which of the following is an example of dysbiosis?
Following extended use of amoxicillin, your patient develops oral thrush as a result of the overgrowth of Candida albicans.
Group B streptococci (GBS) are known to cause life-threatening disease in some newborns, but are commensals in the adult female vagina. Which of the following helps to explain why GBS acts as a pathogen in newborns and as a commensal in healthy adults?
- Newborns have reduced immunity compared to healthy adults.
- Newborns lack firmly established normal flora that compete with the opportunistic pathogen
- Even if a pathogen successfully invades its preferred host tissue, it may not necessarily cause disease.
- Most emerging pathogens have expanded host or tissue range.
involve a dynamic give-and-take between the microbe and the host.
Examples of healthy host-microbe interactions with our normal microbiota include all except
Which factors may result in a normal microbiota species causing disease?
dysbiosis due to antibiotic therapy or invasion of other tissues by the microbiota species
Which statement shows an example of a commensal species in one host becoming a pathogenic species in another host?
Up to 30% of pregnant women harbor Group B streptococci in the vagina to no ill effect, but when transmitted to their newborns, a proportion of babies develop serious infection.
The preference of a pathogen for a specific host is
Which factor is responsible for many emerging pathogens in humans?
expanded host or tissue range of the pathogen
More than half of new infectious diseases in humans emerged due to expanded host tropism by the infectious organism. True or False?
Both Vibrio cholerae and Salmonella typhi are capable of causing disease inside of otherwise healthy individuals. The ID50 of V. cholerae is 1,000,000 cells, while the ID50 of S. typhi is 10,000 cells. Based on this information, which of the following statements is true?
Both V. cholerae and S. typhi are pathogenic, but S. typhi is more virulent than V. cholerae.
Which of the following is/are examples of virulence factors?
Which of the following factors contribute to the evolution of virulence factors?
Host normal microbiota balance
Competency of host immune system
Presence of antibiotic in the environment
Which of the following is the best definition for the term attenuated?
A microorganism that is infectious but is weakened to the point of being unable to cause disease in an immunocompetent host
A virulence study was performed using Staphylococcus aureus in mice. It was determined that the LD50 for the S. aureus alpha-toxin was 0.045 µg/kg of body weight toxin (a relatively low LD50). In the same mouse population, the ID50 was determined to be 200,000 cells (a relatively high ID50). What do these results taken together mean?
This S. aureus strain is less infectious, but its alpha-toxin is highly-toxic.
Bacillus anthracis is a Gram-positive bacterial pathogen known to cause anthrax. B. anthracis secretes a three-protein toxin: protective antigen, lethal factor, and edema factor. Protective antigen binds the host cell surface at cell receptor TEM8. Following proteolytic cleavage, protective antigen forms a membrane channel that allows the passage of lethal factor and edema factor into the cytoplasm. Once inside, edema factor acts as an adenylate cyclase, while lethal factor acts as a zinc metalloprotease, both leading to reduced host cell signaling. Anthrax toxin is best described as a(n)
Type III exotoxin.
Which of the following symptoms and signs of infection are associated with septic shock?
Tachycardia (increased heart rate)
A feeling of disorientation
The degree or extent of disease that a pathogen causes is
Which is not a category of virulence factors?
Properties that contribute to virulence
are determined by both the microbe and the host, and may evolve over time.
What is an example of a virulence factor that is related to immune system evasion?
An attenuated pathogen
has lost virulence factors needed to cause disease in an immune competent host.
the number of cells or virions needed to establish an infection in 50 percent of exposed hosts.
Gram-negative bacteria is a type of
Which type of bacterial toxin is matched INCORRECTLY with its description?
toxemia: a toxin produced during a viral infection
secreted and the targets of some childhood vaccines
Toxemia is a condition
where a toxin has entered the bloodstream resulting in systemic effects.
A microbe is either pathogenic or it is not. A microbe is either virulent or it is not. Both pathogenicity and virulence are all-or-nothing terms.
A microbe with a low ID50 does not necessarily cause severe disease.
Septic shock is typically associated with
Bacillus cereus is naturally found in the soil. B. cereus is known to contaminate rice, which, if undercooked and ingested, can lead to gastroenteritis. In this example, the reservoir for B. cereus is the _________, and the source of infection is the __________.
Which of the following is an example of a direct contact transmission?
An individual contracts rabies after being bitten by a rabid raccoon.
The primary difference between a biological and a mechanical vector is that:
biological vectors play a role in the pathogen's life cycle, whereas a mechanical vector spreads disease without being integral to a pathogen's life cycle
Your college-aged patient presents to you with infectious mononucleosis. You observe the classic triad of lymphadenopathy, fever, and pharyngitis, which began one-day prior (on August 30th). After reviewing her case history, you observe that your patient may have been exposed to her infected roommate about 6 weeks ago (on July 15th). About 2 weeks ago (on August 15th), the patient developed fatigue, malaise, and myalgia. Based on this history, which period represents the prodromal period?
Between August 15th and August 29th
Patients infected with Herpes simplex virus-1, the causative agent of fever blisters, go through periods of viral inactivity (where no active oral cankers appear) and outbreaks (where fever blisters are present). This type of individual is best defined as a(n)
Which of the following is an endogenous source of infection?
bacteria from the skin entering a surgical incision
Which of the following is an indirect infectious disease transmission mode?
Which of the following infectious disease transmission modes is not correctly paired with an example?
It is called a ________________ vector when the vector organism has a role in the pathogen's life cycle.
What is the order of the five stages of infectious disease?
incubation period, prodromal phase, acute phase, period of decline, convalescent phase
If you had to choose to be either a chronic carrier or an asymptomatic carrier, which would you choose any why?
asymptomatic carrier because I wouldn't experience any symptoms
The source of an infectious agent is the animate or inanimate habitat where the pathogen is naturally found.
The acute phase of an infectious disease, when the pathogen levels are the highest, is the most contagious stage of any pathogen.
Which of the following descriptions provides the best definition for mortality rate?
The number of deaths during a specific time period
One out of every 1,000 children who contract measles will develop encephalitis. This statistic is a measure of
What is the definition of morbidity?
existence of disease
When two things happen at the same time, that correlation indicates one factor is causing the other.
The normal function of the PrP protein in mammals is believed to be:
assisting in normal synaptic development and function
How do normal prion proteins (PrP) differ from the infectious prion proteins?
Normal PrP have alpha-helices; infectious PrP have beta-pleated sheets.
How does the number of infectious prions increase?
Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion
Why are the beta-pleated multimers of PrP potentially pathogenic?
The multimers are more stable and resistant to protease.
Which of the following prion diseases is found in deer and elk?
Chronic wasting disease
Which of the following prion diseases was also known as laughing disease?
Which of the following conditions in humans is linked to bovine spongiform encephalopathy?
Variant Creutzfeldt-Jakob disease
What part of the nervous system is most affected by fatal familial insomnia?
Where does the name "scrapie" come from?
The prion disorder causes infected sheep to scrape against objects until their skin is raw.
From which phrase is the term "prions" derived?
Proteinaceous infectious particles
In what year did Stanley Prusiner discover prions?
Which disease did Stanley Prusiner first identify as being caused by prions?
How are prions different from other infectious agents?
They lack nucleic acid.
How are viruses different from eukaryotic cells?
They require a host in order to reproduce.
What is the function of the structural elements of a virus?
To package and protect the viral genome
Chlamydia trachomatis is an obligate intracellular bacterium that causes the sexually transmitted disease chlamydia. When this bacterium was first discovered, it was classified as a virus. However, it was later re-classified as a bacterium. Which of the following is the most likely reason why C. trachomatis was reclassified as a living bacterial cell as opposed to a nonliving viral particle?
Chlamydia trachomatis is capable of performing metabolic processes.
Which of the following are ways that viruses differ from prokaryotes and eukaryotes?
- viruses are not considered alive
- viruses are classified as acellular particles
- viruses are incapable of replicating independently from a host cell.
The rabies virus primarily affects the nervous system. The specificity that the rabies virus has for neuronal host cells is primarily dictated by
the spikes that protrude from its viral envelope.
You are studying an unknown virus that does not perform transcription to make viral proteins. Which of the following characteristics must also be true for this unknown virus?
The virus has a positive, sense-stranded RNA genome
Which of the following genome types has been observed in viruses?
Choose the correct statement about viral evolution.
RNA viruses mutate faster than DNA viruses due to a lack of proofreading replicative enzymes.
In the Spring of 2009, a novel H1N1 virus emerged that had a new combination of genes from pigs, humans, and birds. As a result, the virus spread quickly, resulting in a swine flu pandemic. Which of the following concepts explains why the outbreak occurred?
Viruses are considered to be non-living pathogens for which reason?
their lack of metabolic processes
Compared to both prokaryotic and eukaryotic cells, viruses
are generally smaller.
A previously undescribed infection has been detected among inhabitants in an isolated village in a remote tropical rainforest. When serum from an infected individual is passed through a filter, the infection can be transmitted to laboratory animals. Nothing is observed when the serum is examined with a light microscope at the highest magnification. Biochemical tests show the presence of RNA and protein but no carbohydrates or lipids. This data is consistent with what type of infectious agent?
Which statement is not true about the virus capsid?
Because the capsid is not essential to the virus, it is not a useful target for antiviral drugs.
When a virus has an envelope
it likely escapes its host cell by budding.
allow the virus to attach and enter host cells, may be a target for the host immune system, and show specificity in binding to particular structures on the host cell.
soccer ball (sphere-like with multiple sides)
Which genomic arrangement has not been found in viruses?
a combination of DNA and RNA in the same virus
All viruses must use their genome to produce ______________, which is then used by the host cell to produce _______________.
Retroviruses use the enzyme reverse transcriptase to
direct the production of DNA from a single-stranded RNA genome
A newly-discovered double-stranded RNA virus which infects animal cells is found to contain a unique enzyme which synthesizes double-stranded RNA using an RNA template. Which of the following statements is likely to be true?
The virus must bring this enzyme into the host cell as synthesizing RNA from an RNA template does not happen in animal cells.
Which of the following are contributors to viral genome evolution?
quick replication time and the large number of virions released within a host
Which description of antigenic drift and antigenic shift in the influenza virus is incorrectly matched?
Antigenic drift: Often involves reassortment of viral strains in an animal host followed by a "species jump" to humans.
Both viruses and prokaryotes reproduce by binary fission.
The shape of a virus may be determined by either its capsid or its envelope.
Your elderly patient is affected by shingles. After careful observation, you note that the virus responsible for the infection has an icosahedral capsid, is enveloped, and has double-stranded linear DNA as its genetic material. Based on this information, in which of the following viral families would you group this viral pathogen?
Which of the following observations supports the statement that cytomegalovirus (CMV) has a remarkably broad tropism?
CMV can infect connective tissue cells and parenchymal cells of virtually any organ
Which of the following names represents a viral order?
Which property is not used to classify viruses?
tissue types infected
Which viral family and representative disease contains single-stranded+ RNA and reverse transcriptase?
All the following are DNA viruses except
Viruses which infect many different tissues types are said to have a(n)
The number of species that a specific virus infects is called its host range while the types of tissues that the virus infects is called tropism
You observe that a novel virus penetrates the host cell through membrane fusion. Which of the following statements must also be true regarding this virus and its replicative cycle?
The virus releases from host cells by budding.
An elderly patient who contracted chickenpox as a child now has shingles as an adult. You explain to your patient that both diseases are caused by the same virus, which lays dormant in the body prior to reactivation. Based on this information, choose the true statement.
During dormant periods, the virus exists episomally inside of infected host cells.
Your patient has purple, red, and brown lesions on the legs, indicative of Kaposi sarcoma. Given this observation, which of the following oncogenic viruses is most likely present in your patient?
Human herpes virus-8
Which stage of animal virus replication may be blocked by a drug that binds with the viral spike?
HIV, the virus which causes AIDS, interacts with two receptors on the host cell membrane: CD4 and CCR5. A small percentage of individuals have a genetic mutation which causes their cells to lack CCR5. These individuals will never develop AIDS nor are they able to pass HIV on to others. Which part of viral replication is being blocked by the lack of a receptor?
HIV cannot attach to the host cell without the proper membrane receptor
Which stage of animal virus replication will not be different between naked viruses and enveloped viruses?
Which statement is not true about chronic persistent viral infections?
May involve periods of flare-up where the virus is actively replicating alternating with periods of dormancy.
stimulate uncontrolled host cell division
Which is not a cancer linked to a specific virus?
Like bacteriophage, when an animal cell virus enters a host cell, only the genome enters while the capsid remains outside the cell.
Naked viruses usually exit the animal host cell by budding while enveloped viruses exit by lysis.
All persistent viral infections occur when the virus integrates into the host cell DNA to form a provirus
Which of the following is an unsuitable culture method for an animal virus?
Direct inoculation of virus onto blood agar
A nurse experienced an accidental needle stick while treating a patient who has hepatitis C. The seroconversion window for hepatitis C is approximately 6-8 weeks. Given this information, which of the following viral detection methods would be most appropriate for detecting a hepatitis C infection in the nurse one week following the needle stick?
PCR-based detection of hepatitis C RNA
While hiking, your patient was bitten by a rabid raccoon. Your patient denies having any previous rabies vaccinations. Which of the following antiviral medications should be administered to your patient to prevent viral attachment to host cells?
A young patient who underwent surgical placement of depth electrodes for epilepsy treatment contracted a prion disease. Cortical electrode probes are known to be reused in patients. Based on this information, which of the following prion diseases did the young patient most likely contract?
Iatrogenic Creutzfeldt-Jakob Disease
Animal viruses can be grown in all of the following except
E. coli cells.
When mixed with their host bacterium and plated on solid agar, lytic phage will form clear areas in the bacterial growth. What are these clear areas called?
Which of the following tests works by detecting viral nucleic acid?
An individual uses an in-home test kit one week after engaging in high-risk behavior for HIV infection. The test kit uses a saliva sample that is mailed to a lab where an agglutination test to detected HIV antibodies is run. The results come back negative for HIV. What should the patient consider regarding these test results?
One week may not be enough time for HIV antibodies to be detected
Challenges in developing effective antiviral drugs with minimal side effects to the patient include
viruses use the cell's own machinery and metabolism for replication.
Which of the following antiviral drug categories is incorrectly matched with its description?
Interferons: Used for postexposure prophylaxis
misfolded proteins which can cause normal versions to also misfold
Which of the following prion diseases may be acquired by eating beef contaminated with a cattle prion?
Both agglutination and ELISA procedures may be used to detect the presences of either viral antigen or the patient's antibodies to a virus.
Antiviral drugs exist that target all stages of viral replication except the production of viral nucleic acids.
What is the most likely etiology (cause) of this spongiform disease?
What is the incubation period of spongiform?
Is spongiform contagious?
No, the disease is not contagious.
Which test confirmed the presence of this spongiform disease?
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