BIOL2300 Exam I PQ

Home-canned foods should be boiled before consumption to prevent botulism. Considering that this treatment does not destroy endospores, why would it prevent the disease?

It destroys any exotoxin that the bacteria might have produced.

Why does Mycobacterium tuberculosis direct macrophages to engulf them?

It avoids a process that could lead to activation of the macrophages.

What is the role of lactoferrin?

It binds iron, removing it as an element source that would otherwise support microbial growth.

How could colony-stimulating factors be used as a therapy?

It can be used to direct the accumulation of a given cell type.

Describe two general events that can initiate inflammation.

Invasion by microorganisms and tissue damage

How is an enterotoxin different from endotoxin?

An enterotoxin is an exotoxin that affects intestinal cells. Endotoxin is the LPS component of the Gram-negative outer membrane.

________________ are indifferent to the presence of oxygen and do not use it. A. Aerotolerant anaerobes B. Facultative anaerobes C. Obligate aerobes D. Microaerophiles E. Obligate anaerobes

A. Aerotolerant anaerobes

Tuberculosis is characterized by granulomas called tubercles. What is a granuloma?

A concentrated group of macrophages, giant cells, and T cells that surrounds microbes or material that cannot be destroyed

Why might a person immunized against cholera contract the disease anyway?

A new serotype of Vibrio cholerae has emerged; previous immunity does not ensure immunity against this capsulated strain.

What is a type III secretion system?

A structure bacteria use to inject molecules into a host cell.

How does fever inhibit the growth of pathogens?

A temperature above a microbe/s optimum growth temperature can cause the growth rate to decline sharply.

Which of the following bacteria lack a periplasmic space? A. Neisseria gonorrhoeae B. Staphylococcus aureus C. Escherichia coli D. A and C E. A, B and C

B. Staphylococcus aureus

Which of the following groups of organisms is least likely to cause disease in humans? A. Archaea B. Eucarya C. Protozoa D. Bacteria E. Fungi

A. Archaea

Bacterial endotoxin is characterized by all the following: A. Consists of LPS. B. Determines bacterial shape. C. May have different effects depending on the specific bacterial source. D. Is toxic due to the effects of the polysaccharide side chains. E. A and C.

A. Consists of LPS

Why are viroids resistant to nucleases? A. Having a circular RNA 'genome,' they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA). B. Having a circular RNA 'genome,' with no protein shell, they are resistant to the protein-degrading activities of nucleases. C. Nucleases will only digest DNA, not RNA-so viroids are protected. D. Viroids have only been identified in plants. Plant nucleases cannot digest RNA.

A. Having a circular RNA 'genome,' they are resistant to the digestion of most exonucleases (that nibble/digest the free ends of RNA or DNA).

Which of the following is NOT a characteristic of the bacterial cell membrane? A. It maintains cell shape. B. It is composed of a phospholipid bilayer. C. It contains proteins. D. It is the site of cell wall formation. E. It is selectively permeable.

A. It maintains cell shape

Which of the following is not a characteristic of the bacterial cell membrane? A. It maintains cell shape. B. It is composed of a phospholipid bilayer. C. It contains proteins. D. It is the site of cell wall formation. E. It is selectively permeable.

A. It maintains cell shape

The family to which the Rhinovirus belongs is the A. Picornaviridae B. Enterovirus C. Enteroviridae D. Picornavirus E. Herpesviridae F. A and D

A. Picornaviridae

The etiologic agent of dental caries is: A. Streptococcus mutans B. Staphylococcus aureus C. Streptococcus pyogenes D. Staphylococcus epidermidis E. Lactobacillus acidophilus

A. Streptococcus mutans

The nucleus A. is a double membrane sac containing DNA and is found in eukaryotes. B. is a single phospholipid membrane sac containing prokaryotic DNA. C. is a smaller structure contained within the eukaryotic nucleolus. D. cannot transport molecules to the cytoplasm due to the double membrane barrier. E. A and D

A. is a double membrane sac containing DNA and is found in eukaryotes

Why are diseases caused by opportunists becoming more frequent?

Advances in medical care can keep the people alive longer and some of the interventions require surgery or immunosuppressive drugs.

What is an A-B exotoxin?

An A-B exotoxin (protein) has two parts, A and B. The B portion binds a host cell, thereby delivering the A portion, which has toxic activity.

Inanimate objects capable of transferring infectious disease agents are: A. Pathogens B. Fomites C. Virulence factors D. Carriers E. B and D

B. Fomites

Choose the incorrect statement(s) about lysozyme. A. It is found in tears and saliva. B. It prevents cross-linking of adjacent glycan chains. C. It is generally more effective against Gram-positive organisms. D. It breaks the bond that links the NAG and NAM molecules of peptidoglycan.

B. It prevents cross-linking of adjacent glycan chains

Choose the incorrect statement(s) about lysozyme. A. It is found in tears and saliva. B. It prevents cross-linking of adjacent glycan chains. C. It is generally more effective against Gram-positive organisms. D. It breaks the bond that links the NAG and NAM molecules of peptidoglycan. E. A and D

B. It prevents cross-linking of adjacent glycan chains

Choose the Gram-positive acid-fast rod that is a human pathogen. A. Clostridium tetani B. Mycobacterium tuberculosis C. Streptococcus mutans D. Mycoplasma pneumoniae E. Bacillus anthracis

B. Mycobacterium tuberculosis

An antibiotic is added to a culture of E. coli, resulting in death of the cells. Bacteriophages are then added. Would the phage replicate in the E. coli cells? Why or why not? A. Yes, because the machinery inside the cells is most likely still active, even though the cells are no longer living. The virus could use that machinery to replicate new virus particles. B. No, because the virus would depend too much on having the active machinery of a living cell for its replication. Without the ability of the cell to try to replace what is lost/damaged/used as the virus goes through its life cycle, the virus couldn't reproduce effectively. C. Yes, because viruses are capable of reanimating dead cells to force them to produce more virus particles. D. No, because entry of the virus into the target cell is dependent on the cell being alive to conduct endocytosis of the virus.

B. No, because the virus would depend too much on having the active machinery of a living cell for its replication. Without the ability of the cell to try to replace what is lost/damaged/used as the virus goes through its life cycle, the virus couldn't reproduce effectively.

Why would the discovery of TLRs alter the view that innate immunity is non-specific?

Because they allow cells to detect patterns associated with microbes, indicating that the responses involve some specificity (although not the molecular specificity that characterizes the adaptive responses).

Why can bone marrow transplants be used to replace defective lymphocytes?

Bone marrow has hematopoietic stem cells; in the procedure for a bone marrow transplant, the lymphocytes are destroyed and then another person's bone marrow (containing hematopoietic stem cells) is transferred. The transferred stem cells can develop into new lymphocytes (as well as other blood cells).

From a virus's perspective, why would it be beneficial to prevent apoptosis?

By allowing the cell to survive longer, the viruses have more time to multiply.

Which of the following structures do bacteria use for attachment to surfaces or to each other? 1. capsule 2. LPS 3. flagella 4. pili 5. fimbriae A. 1, 4 B. 1, 2, 5 C. 1, 3, 4 D. 1, 4, 5 E. 1, 2, 3, 4, 5

D. 1, 4, 5

A 5 YO child died from severe septic shock, disseminated intravascular coagulation (clotting), and cardiac insufficiency (failure) following a sudden onset of fever, severe headache, and vomiting. The causative agent, a Gram-negative diplococcus, was isolated from blood and cerebrospinal fluid (CSF) on selective agar. What is the most important virulence factor involved in disease production by the etiologic agent in this case? A. Exotoxin production B. Flagella C. Lipopolysaccharide D. Pili E. Polysaccharide capsule

C. Lipopolysaccharide

Peptidoglycan A. May be digested by penicillin. B. Consists of a long string of NAG coupled to a long string of NAM. C. May be digested by lysozyme. D. Protects the eukaryotic cell from osmotic lysis. E. B and D.

C. May be digested by lysozyme

A hot tub would most likely contain___________________. A. Psychrophiles B. Thermophiles C. Mesophiles D. Hyperthermophiles E. Partier-o-philes

C. Mesophiles

Which of the following terms does NOT refer to bacterial morphology? A. vibrio B. coccus C. Sarcinae D. bacillus E. pleomorphic

C. Sarcinae

What are siderophores?

Iron-binding molecules

Explain why an IV catheter poses a risk to a patient.

Catheters are invasive and breach first-line barriers. They can introduce pathogens into the normally sterile urinary bladder where organisms can multiply and cause infection.

What factor favors abundant growth of Clostridium difficile in the intestine?

Clostridium difficile does not compete well with members of the normal intestinal microbiota; if those organisms are inhibited, such as by antibiotics, then the organism can grow to high numbers.

What political and societal factors might lead to a decrease in childhood immunizations?

Complacency, war, civil unrest

Endospores A. are ubiquitous in the soil. B. are a reproductive form of the bacterium. C. are formed by members of the genera Clostridium and Bacillus. D. A and C E. A, B, and C

D. A and C

Identify the true statement(s). A. In microbiology, growth usually refers to an increase in size of the bacteria. B. Organisms that are large, complex, single-celled, lacking a rigid cellulose cell wall, and frequently classified by means of locomotion are yeasts. C. Drugs that target prokaryotic protein synthesis would have no effect on eukaryotic cell growth. D. Both prokaryotic and eukaryotic cells have a glycocalyx. E. A and D

D. Both prokaryotic and eukaryotic cells have a glycocalyx

Extrachromosomal DNA is found in all of the following EXCEPT: A. Mitochondria B. Chloroplasts C. Plasmids D. Nucleoid E. B and D

D. Nucleoid

A sterile item is free of all of the following EXCEPT: A. Microbes B. Endospores C. Viruses D. Prions E. Oocysts

D. Prions

Attributes of an organism that promote pathogenicity are called: A. Chronic disease factors B. Colonization factors C. Mutualistic factors D. Virulence factors E. Acute disease factors

D. Virulence factors

Which of the following does Streptococcus pneumoniae use to survive in the host? A. plasmids B. pili C. flagella D. capsules E. endotoxin F. phagocytosis G. fimbriae H. D and G

D. capsules

Bacteriophages and animal viruses A. both may enter a host cell by endocytosis. B. both may enter a host cell by fusion. C. both involve entry of the entire nucleocapsid. D. differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

D. differ because bacteriophages leave the capsid outside the cell, while animal virus entry involves the entry of the whole nucleocapsid.

Infection of the fallopian tubes can lead to infertility. Why would this be so?

Damaged tissue is replaced by scar tissue, which can block a fallopian tube.

What is the importance of keratinase?

Dermatophytes produce the enzyme, which breaks down keratin. This protein is found in superficial skin cells and provides a nutrient source for the fungi.

What could a microorganism do to avoid engulfment?

Destroy C5a (a complement protein that attracts phagocytes), destroy phagocytes, attract complement regulatory proteins to avoid the opsonizing effects of complement. This general topic is discussed in chapter 16.

Penicillin would be most effective against: A. Non-growing bacteria. B. Vegetative bacterial cells. C. Gram-positive bacteria. D. Gram-negative bacteria. E. B and C.

E. B and C

Colonization of the body is inhibited by A. the shedding of skin cells B. the movement of mucus by cilia C. peristalsis D. the flushing action of the urinary tract E. All of the choices are correct.

E. all of the choices are correct

The receptors to which animal virus attachment proteins usually bind are A. proteins B. carbohydrates C. nucleic acid D. lipids E. glycoproteins F. glycolipids G. LPS H. LTA fibers

E. glycoproteins

Describe two changes in cells undergoing apoptosis.

Enzymes cut the DNA and portions of the cell bud off

Describe three mechanisms pathogens may use to survive within phagocytic cells.

Escape from the phagosome, prevent phagosome-lysosome fusion, and survive within the phagolysosome.

Lysogenized cells A. are immune to any further infection by any virus. B. are immune to infection by the same virus. C. may have new properties. D. respond to infection with the SOS response. E. A and B F. B and C

F. B and C

Disease(s) in which the causative agent becomes latent is/are A. cold sores (HSV-1) B. genital herpes (HSV-2) C. human papilloma virus (HPV) D. shingles (VZV) E. human immunodeficiency virus (HIV) F. Rhinovirus G. Streptococcus pneumoniae H. A, B, C, D and E F. All of the choices are correct.

H. A, B, C, D AND E

Describe two ways in which infectious agents can be transmitted to a patient.

Infectious agents may be transmitted to patients by invasive medical devices, unsterile instruments or supplies. They may be directly transmitted by healthcare workers or other patients. They may be inhaled.

How is mutualism different from commensalism?

In mutualism, both partners benefit, whereas in commensalisms, only one partner benefits.

Explain the difference between incidence of a disease and prevalence of the disease.

Incidence describes the number of new cases in a region during a specific time period; prevalence describes the total number of cases in a region during a specific time period.

Why is it a good strategy for a microbe to adhere to a receptor that plays a critical function for a host cell?

It is unlikely that the host cell will stop producing the receptor (mutations in the receptor gene would be lethal).

How does the mucociliary escalator protect against infection?

It moves microbes out of the airways.

From a pathogen's standpoint, why would it be beneficial to bind regulatory proteins that inactivate C3b?

It prevents both opsonization by C3b and complement activation.

What is the function of a colony-stimulating factor (CSF)?

It promotes the development of certain cell types.

How were Koch's postulates used to prove the cause of anthrax?

Koch grew Bacillus anthracis from all anthrax cases examined; he introduced pure cultures of the organisms into healthy susceptible mice, again causing the disease anthrax. Finally, he recovered the organism from the experimentally infected mice.

Why can Koch's postulates not be used to identify the causes of diseases due to polymicrobial infections?

Koch's postulates require that pure cultures be used, and by definition, polymicrobial infections are involve multiple species acting together.

How are macrophages related to monocytes?

Macrophages descend from monocytes; the monocytes circulate in blood, and as they enter the tissues, they develop into macrophages.

The body's own cells do not trigger the alternative pathway of complement pathway activation. How come?

Molecules in host cell membranes bind regulatory proteins that will inactivate any C3b molecules that attach to the membrane.

Why would it be difficult to study invasion of mucous membranes?

Mucous membranes are complex environment, with many signals coming from the environment and other cells.

Which type of granulocyte is the most abundant?

Neutrophils

List two sensor systems of the innate defenses.

Pattern recognition receptors; complement system

The rate of nosocomial infections is often relatively high in emergency room settings. Explain why this might be so.

People often have broken skin after accidents, or receive IV fluids in the ER. They may be exposed to an infectious disease before it is diagnosed and quarantined. Personnel are working rapidly and may not carefully wash their hands or change their clothing between patients.

Explain why we have relatively accurate data on the number of cases of measles that occur in the United States but not on the number of cases of the common cold.

People will go to the doctor more often with measles, but will often self-medicate a cold. Moreover, the common cold is not a reportable disease; measles is reportable.

What molecules might pattern recognition receptors (PRRs) recognize?

Peptidoglycan, LPS, flagellin (and others)

On what three factors does a descriptive study focus?

Person, place, and time

Encapsulated organisms can be phagocytized once antibodies against the capsule have been produced. Why would this be so?

Phagocytes have receptors for the Fc portion of antibodies. So once an antibody has bound to a cell, the phagocyte can attach.

How does a phagolysosome differ from a phagosome?

Phagolysosomes have fused with lysosomes, and therefore they contain the enzymes and toxic substances of lysosomes.

Why would relatively few people of West African ancestry have the Duffy blood group antigen?

Plasmodium vivax attaches to the Duffy blood group antigen, so people that lack the antigen are more likely to survive and have children.

Give an example of a microbe that causes a latent infection.

Several examples are possible, including Mycobacterium tuberculosis, Herpesviruses, and HIV.

What factors might contribute to a long incubation period?

Slow growth of a pathogen, low infecting dose (it would take additional for the organisms to grow to high numbers), time for pathogen to reach the body site where it can replicate and/or cause damage.

Explain why smallpox was successfully eradicated, but rabies probably never will be.

Smallpox only affected humans, had distinctive identifiable symptoms, and vaccination was possible. Rabies is found in a number of both wild and domestic hosts, and may be transmitted before symptoms are evident.

Why would macrophages have TLRs in their endosomal membranes?

So they can determine if they have engulfed microbial invaders (as opposed to normal host components).

What are endogenous and exogenous pyrogens?

Substances that induce fever; cytokines are endogenous pyrogens whereas microbial products are exogenous pyrogens

If a cell produces antiviral proteins, what happens to that cell when those proteins encounter long dsRNA?

The cell shuts down protein synthesis, eventually leading to apoptosis.

How is the timing of a propagated epidemic related to the incubation period of the pathogen?

The time between the onset of symptoms in the index case and the onset of symptoms in the next case(s) reflects the incubation period of the disease.

Syphilis was once treated by infecting the patient with the parasite that causes malaria, a disease characterized by repeated bouts of fever, shaking, and chills. Why would this treatment cure syphilis?

The high fever that develops as a result of malaria is above the optimum growth temperature of the bacterium that causes syphilis.

Explain how a low dose of an infecting organism can result in an asymptomatic infection.

The immune system may be able to overcome the organism before it multiplies enough to cause symptoms.

What is a ligand?

The molecule that binds to a given receptor

How would damage to the ciliated cells of the respiratory tract predispose a person to infection?

The mucociliary escalator would no longer function properly, so microbes wouldn't be removed from the airways.

Why would various unrelated viral infections often include a similar set of symptoms (fever, headache, fatigue, and runny nose)?

The symptoms are often due to the immune response to the viruses.

Why would the immune response to members of the normal microbiota cross-react with pathogens?

The two groups of microorganisms share certain antigens.

What is the MMWR?

The weekly newsletter published by the Centers for Disease Control and Prevention; stands for Morbidity and Mortality Weekly Report.

How do cytomegaloviruses avoid the cellular immune response?

Their genome encodes "fake" MHC class I molecules. When these are produced, the virally-infected cell is not a target for Tc cells or NK cells.

Describe how Fc receptors prevent phagocytosis.

They bind the part that the innate defenses normally recognize, orienting the antibody so that the Fab region, which the innate defenses have no mechanism for recognizing, faces away from the cell.

Describe the dual roles played by some types of phagocytes.

They destroy invaders and also communicate with components of the adaptive immune system to enlist their help.

How do Shigella species enter intestinal epithelial cells?

They use a type III secretion system to induce the cells to take them up. First, however, they must get to the base of the mucosal epithelial cells, which they do by being transported via M cells.

How do the African trypanosomes avoid the effects of antibodies?

They use antigenic variation, changing the surface proteins they produce to stay ahead of the adaptive immune response.

Why is it important to include a placebo in a scientific study to assess the effectiveness of a drug?

Use of a placebo will allow you to confirm that any improvement is due to receipt of an effective drug and not due to other factors that may be present in the testing situation.

How would you expect a trend toward warmer climates to affect the spread of vector-borne disease?

Vectors can extend into regions of warmer climate and expand the potential for vector-borne disease.

Circulating blood is not normally released from the body. Describe how blood-borne microbes might exit.

Vectors suck blood, allowing microbial exit, and both internal and external injuries hemorrhage.

What role does C3b play in opsonization and complement system activation?

When many molecules of C3b are bound to a particle, macrophages can more easily engulf the particle (opsonization); when even a few molecules of C3b are bound to a particle, other complement components can bind, leading to activation of the complement system.