Deck 2: Host-Parasite Interaction

Question 1

This type of bacteria is able to live in the colon with little to no oxygen and is the predominant organism.

A) Anaerobes
B) Facultative anaerobes
C) Facultative gram-negative rods
D) Gram-positive cocci

Answer 1

A
Anaerobes make up over 90% of the microbial flora of the large intestine.The facultative anaerobes,facultative gram-negative rods,and gram-positive cocci are present in the colon in much smaller numbers than the anaerobes.

Question 2

This bacterial state occurs when a host harbors a disease-causing organism,but does not show signs of disease.

A) Carrier
B) Transient
C) Resident
D) Indigenous

Answer 2

A
Transient,resident,and indigenous refer to particular types of flora associated with the human body,whereas carrier refers to the state in which pathogenic organisms establish themselves in a host without causing disease,but the host can still transmit the infection.

Question 3

The stomach can be considered the first line of defense against microbial infections because:

A) Most microorganisms are susceptible to the antibiotics and alkaline pH present in the stomach.
B) Most microorganisms are killed by the liver enzymes that are emptied into the stomach during a meal.
C) The stomach produces lipase, which attacks the lipopolysaccharide cell wall of the organisms.
D) Most microorganisms are susceptible to the acid pH of the stomach.

Answer 3

D
The stomach cells secrete enough acid to create an environment with a pH of approximately 1.Bacteria that are enmeshed in food,spore-forming bacterial species in their spore phase,and the cysts of parasites can survive the extreme pH present in the stomach.The stomach does not produce antibiotics or lipase,and liver enzymes do not empty into the stomach during digestion.

Question 4

Factors that determine the pathogenicity and increase the virulence of organisms include all the following EXCEPT:

A) An organism's ability to avoid phagocytosis
B) An organism's ability to produce exotoxins and extracellular enzymes
C) An organism's ability to produce infection when host conditions change
D) An organism's ability to survive intracellularly when phagocytized

Question 5

All the following are considered pathogenic organisms found in the nasopharynx of healthy individuals EXCEPT:

A) Haemophilus influenzae
B) Streptococcus pneumoniae
C) Moraxella catarrhalis
D) Neisseria meningitidis

Question 6

What mechanism allows strict anaerobes to grow in the cervices and areas between the teeth when plaque is present?

A) A low oxidation-reduction potential occurs at the tooth surface under the plaque.
B) The bacteria secrete sugar to nourish the strict anaerobes.
C) The normal florae secrete antibiotics to kill all the other bacteria and allow the strict anaerobes to thrive.
D) The plaque-causing bacteria secrete an alkaline fluid and change the pH around the tooth.

Question 7

The human body is constantly challenged by pathogens in the environment.It is not infected by every pathogen it encounters because the microbial florae:

A) Engulf the pathogenic bacteria
B) Produce conditions at the microenvironmental level that block colonization
C) Prime our immune system
D) Activate and support the action of antigen-presenting cells, cytokines, and cell-mediated immunity

Question 8

Diabetics may sometimes be infected with their own resident florae.This type of infection is called:

A) An opportunistic infection
B) A carrier state
C) Symbiosis
D) A parasitic infection

Question 9

A laboratory professional is testing a new antimicrobial soap.The tech washes her forearm,then does a culture of the skin.Which organisms should she expect to find growing in the culture?

A) Diphtheroids and Bacillus spp.
B) S. epidermidis and Propionibacterium
C) S. aureus and Propionibacterium
D) Diphtheroids and Propionibacterium
E) None of these organisms should be found.

Question 10

The most common bacterial characteristic that allows for evasion of phagocytosis by the host is:

A) Exotoxin production
B) Extracellular enzyme production
C) Pili
D) Polysaccharide capsule

Question 11

A patient with an indwelling catheter develops a fever and lethargy.In addition,the urine in the catheter bag has turned a brownish color and is foul-smelling,which indicates an infection.What type of infection does this describe?

A) Opportunistic
B) Iatrogenic
C) Pathogenic
D) Parasitic

Question 12

After perforation of the colon,surgeons must guard against infection in the _____ because of leakage of the contents of the colon.

A) Peritoneal cavity
B) Urinary bladder
C) Vaginal flora
D) Renal vein

Question 13

The smaller the number of microorganisms necessary to cause infection in a competent host,the more _____ the microorganism.

A) Opportunistic
B) Parasitic
C) Invasive
D) Virulent

Question 14

During the childbearing years,the normal florae of the vagina maintain a low pH,thus encouraging colonization with all the following types of organisms EXCEPT:

A) Lactobacilli
B) Gram-negative rods
C) Anaerobic gram-negative bacilli
D) Gram-positive cocci

Question 15

The ability of an organism to produce disease in a susceptible individual is called:

A) Pathogenicity
B) Iatrogenic infection
C) Parasitic infection
D) Opportunistic infection

Question 16

Mechanisms used by the skin to prevent infection and protect the underlying tissue from invasion by potential pathogens include all the following EXCEPT:

A) Desquamation of the epithelium
B) Excretion of lysozyme by sweat glands
C) Antibiotics that inhibit many microorganisms
D) Mechanical separation of microorganisms from the tissues

Question 17

Organisms that participate in a biologic relationship where both benefit from one another are called:

A) Parasites
B) Symbionts
C) Hosts
D) Florae

Question 18

Healthy people are colonized by many different bacteria in many different sites.These bacteria are referred to as:

A) Transient florae
B) Carrier florae
C) Maintenance florae
D) Indigenous florae

Question 19

Parasitism is:

A) A biologic relationship between two or more organisms in which both benefit from one another
B) A biologic relationship between only two organisms in which there are no beneficial or harmful effects to the host
C) A biologic relationship in which one species gains benefits at the expense of the host
D) A synonym for mutualism

Question 20

This is a leukocidin that is lethal to leukocytes and produced by staphylococci.

A) Panton-Valentine
B) Lancefield
C) Hemolysin
D) Adhesins

Question 21

A subsequent exposure to the same antigen elicits a(n)_____,characterized by a rapid increase in IgG antibody associated with higher levels,a prolonged elevation,and a more gradual decline in antibody levels.

A) Primary immune response
B) Anamnestic immune response
C) Opsonin immune response
D) Innate immune response

Question 22

Once infected with Borrelia recurrentis,a 2- to 15-day incubation period follows where high numbers of organisms are found in the blood.The infected individual experiences high fever,rigors,severe headache,muscle pains,and weakness.This febrile period lasts for about 3 to 7 days,but ends quickly with the induction of an immune response.However,a similar but less severe course of symptoms recurs several days to weeks later.What causes this relapse?

A) The organism systematically changes its surface antigens during the course of a single infection.
B) The organism produces extracellular toxins that cause the symptoms.
C) This organism survives inside infected cells and once the cell dies, the organism is released into the blood, causing this relapse.
D) This relapse occurs as the host is trying to mount the secondary antibody response.

Question 23

Healthy skin secretes these substances to help prevent colonization by transient and possibly pathogenic organisms.

A) Long-chain fatty acids
B) Sebaceous glands
C) Bacteriostatic substances
D) Antibodies

Question 24

A physician notices that several patients are infected with Clostridium difficile,but only a few of the patients are symptomatic for disease.The reason for this discrepancy is:

A) Only those strains of the organism carrying the extrachromosomal DNA coding for the toxin gene will produce toxin and cause the individuals to be symptomatic.
B) Only those strains of the organism carrying DNA coding for the toxin within its main DNA molecule will produce toxin and cause the individuals to be symptomatic.
C) The exotoxin produced contains only the nontoxic portion.
D) The exotoxin must be produced in conjunction with extracellular enzymes to cause problems.

Question 25

Immunity to intracellular bacterial pathogens,such as Mycobacterium tuberculosis,is primarily cell mediated,through the activities of:

A) Interferons and macrophages
B) Antibodies and lymphokines
C) Lysozyme, T lymphocytes, and antibodies
D) T lymphocytes, lymphokines, and macrophages

Question 26

After attachment to host cells,a pathogen uses all the following mechanisms to establish itself and cause disease EXCEPT:

A) Uses lactoferrin for iron
B) Produces an IgA protease that degrades the IgA at mucosal surfaces
C) Produces lysozyme to kill the host cell
D) Circumvents host antibodies by shifting key cell-surface antigens

Question 27

One of the most effective defenses bacteria have against phagocytosis is:

A) Enzymes
B) The capsule
C) Plasmids
D) Lipopolysaccharide layer

Question 28

Dissemination of a pathogen is:

A) When a pathogen penetrates and grows in tissues
B) When a pathogen multiplies intracellularly
C) When a pathogen circumvents host antibodies by shifting key cell-surface antigens.
D) When infection with a pathogen spreads from the initial infection site to distant sites such as organs and tissues

Question 29

Lysozyme is:

A) An antibody produced by the skin
B) A low-molecular-weight enzyme that hydrolyzes the peptidoglycan layer of bacterial cell walls
C) An exotoxin that digests the lipopolysaccharide layer of the bacterial cell wall
D) A radical similar to hydrogen peroxide

Question 30

All the following activities must occur for phagocytosis to take place and be effective in host defense EXCEPT:

A) Attachment of the particle to the phagocyte
B) Ingestion
C) Killing
D) Migration of lymphocytes to the area of infection (chemotaxis)

Question 31

These are low-molecular-weight proteins secreted by T cells.

A) Antibodies
B) Opsonins
C) Lymphokines
D) Lysozyme

Question 32

Changes in these host structures can result in lower virulence of a microorganism.

A) Pili
B) Adhesin receptors
C) Surface polysaccharides
D) Phagocytes

Question 33

The major constituents of the adaptive or specific immune response are:

A) Neutrophils
B) Macrophages
C) Monocytes
D) Lymphocytes

Question 34

A patient is brought to the emergency room with the following symptoms: body temperature of 102° F,blood pressure 90/60,a WBC of 2.0 cells/liter,and disseminated intravascular coagulation.This person has gram-negative rods growing in his blood.What is responsible for this condition?

A) Exotoxin
B) Extracellular enzymes
C) Endotoxin
D) Exfoliating toxin

Question 35

Innate immunity consists of all the following components EXCEPT:

A) Physical and chemical barriers such as the skin and mucous membranes
B) Blood proteins that act as mediators of infection
C) Secretion of bacteriocidal substances onto the skin and mucous membranes
D) A cellular mechanism capable of phagocytosis
E) All of the above are part of the innate immune system

Question 36

What virus causes immune suppression in the host by targeting and destroying the host's CD4+ T cells?

A) HIV
B) Hepatitis B
C) Epstein-Barr
D) Cytomegalovirus

Question 37

This class of antibodies is a pentamer.

A) IgM
B) IgG
C) IgA
D) IgE

Question 38

This process results in enhanced phagocytosis by neutrophils.

A) Opsonization
B) Chemotaxis
C) Digestion
D) Glycolysis

Question 39

The effects of endotoxins consist of dramatic changes in all the following EXCEPT:

A) Blood pressure
B) Fluid imbalance
C) Clotting
D) Body temperature

Question 40

Interferon is a substance produced by the body that inhibits viral replication.Interferon accomplishes this task by:

A) Digesting the virus that is attempting to attach to the host cell
B) Destroying the host cell before the virus can attach and replicate
C) Binding to surface receptors that stimulate the cell to synthesize enzymes that inhibit viral replication over several days
D) Stimulating platelets to produce b-lysins

Question 41

This is a form of food poisoning that can be life threatening.

A) S. aureus
B) B. cereus
C) C. difficile
D) C. botulinum

Question 42

The classic example of a bite-wound infection is:

A) Rabies
B) S. aureus
C) Plague
D) Ebola

Question 43

The resulting disease from this route of transmission is a disease of animals that is transmitted to humans.

A) Sexual contact
B) Zoonotic
C) Airborne
D) Ingestion

Question 44

Pathogens can be transmitted through all the following routes EXCEPT:

A) Ingestion
B) Handwashing
C) Sexual contact
D) Air

Question 45

Because infections can be encountered via the air,_____ can cause transmission of some pathogens.

A) Cuts
B) Eyes
C) Coughing
D) Children