Microorganisms and Disease

Q1: Cholera toxin is an A-B type toxin in which the B portions bind to a receptor on a host cell and the A portion enters the cell to cause

A ADP ribosylation of adenylate cyclase that stops production of cAMP

B ADP ribosylation of a G protein that locks it into an active form that stimulates adenylate cyclase to make cAMP

C cleavage of rRNA that results in disruption of ribosome function

D ADP ribosylation of guanylate cyclase that stimulates production of cGMP

ANS:B - ADP ribosylation of a G protein that locks it into an active form that stimulates adenylate cyclase to make cAMP

Overproduce cAMP, which disrupts the fluid and electrolyte balance, causing hyper secretion of chloride and bicarbonate.

Q2: The toxins produced by bacteria

A kill viruses

B encourage bacterial reproduction

C interfere with physiological processes in the body

D all of the above

ANS:C - interfere with physiological processes in the body

No answer description is available.

Q3: Fatalities following influenza infection are usually due to the

A dehydration

B bacterial superinfection

C damage to the heart muscle

D formation of granulomas in the lung

ANS:B - bacterial superinfection

No answer description is available.

Q4: Each of the 3 virulence factors of Bacillus anthracis i.e. the capsule, edema toxin and lethal toxin can affect the activity of

A B cells

B macrophages

C ciliated epithelial cells

D M cells

ANS:B - macrophages

No answer description is available.

Q5: Which of the following disease is not caused by microbial protein toxin?

A Botulism

B Diphtheria

C Shigella dysentery

D Tuberculosis

ANS:D - Tuberculosis

No answer description is available.

Q6: Which of the following disease is caused by DNA viruses?

A Poliomyelitis

B Yellow fever

C Measles

D Small pox

ANS:D - Small pox

No answer description is available.

Q7: The agent responsible for causing mad cow disease is thought to be a

A fungus

B protozoan

C prion

D virus

ANS:C - prion

No answer description is available.

Q8: Which of the following is true regarding anthrax?

A Anthrax is caused by a virus

B Anthrax is highly contagious

C Inhalation anthrax and cutaneous anthrax are caused by separate strains of Bacillus anthracis

D Inhalation Anthrax requires infection with a large number of spores

ANS:D - Inhalation Anthrax requires infection with a large number of spores

Bacillus anthracis (Ba) - A Gram positive aerobic spore forming bacillus.

Q9: Which of these cytokines is also known under the name cachectin?

A Interferon gamma

B Interleukin 2

C Tumor necrosis factor (TNF)

D None of the above

ANS:C - Tumor necrosis factor (TNF)

No answer description is available.

Q10: Which of the following statements is not true regarding Mycobacterium tuberculosis and/or the disease it causes?

A The pathogen contains mycolic acid in its cell wall

B The pathogen can live inside macrophages

C Antibodies to the pathogen are protective

D None of these

ANS:C - Antibodies to the pathogen are protective

No answer description is available.

Q11: The "A" subunit of diphtheria toxin

A binds host cell receptors found on heart cells

B cause ADP ribosylation of a factor involved in protein synthesis

C forms cAMP that leads to fluid accumulation

D lysis macrophages with the release of cytokines

ANS:B - cause ADP ribosylation of a factor involved in protein synthesis

Corynebacterium diphtheria _ a Gram Positive, club-shaped rod often occurring in V-and L-shaped arrangements ("Chinese characters"). Human respiratory bacterium.

Single potent exotoxin damages the pharyngeal mucosal and also circulates in the blood. The toxin is only produced by the strains of C. Diphtheriae that are lysogenized by bacteriophage carrying the tox positive gene.

Diphtheria toxin is a potent ADP ribosyl transferase that ADP-ribosylates EF-2 shutting down Eukaryota protein synthesis in mucosa, heart, and nerves.

Q12: Pseudomembraneous colitis is

A precipitated by the use of certain antibiotics

B caused by a gram-positive bacterium

C caused by a spore-forming bacterium

D all of the above

ANS:D - all of the above

Clostridium difficile is a Gram-positive, spore-forming, anaerobic rod, manifests first as diarrhea and develops into "pseudomemranous colitis" also known as "antibiotic-associated colitis" because it follows antibiotic therapy to treat other bacterial infections.

Produce 2 toxins: Toxin A (an enterotoxin) causes fluid accumulation and damage the mucosa of the large bowel.

Toxin B: A cytotoxin that causes cytoskeltel changes and then kills mucosal cells.

Q13: Which of the following characteristic of the Rotavirus was important for the construction of the Rotashield vaccine?

A The possession of a segmented RNA genome

B A limited number of capsule types

C The ability of monkey Rotavirus strains to cause serious illness (diarrhea) in human beings

D The ability of the Rotavirus to be transmitted faster

ANS:A - The possession of a segmented RNA genome

Rotavirus is a genus of double-stranded RNA viruses in the family Reoviridae. Rotaviruses are the most common cause of diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus at least once by the age of five. Immunity develops with each infection, so subsequent infections are less severe; adults are rarely affected.

Q14: Which of the following is common in the disease caused by Coryne-bacterium diphtheriae and Bacillus anthracis?

A Both organisms are gram-positive spore formers

B Diphtheria toxin and edema toxin are ADP ribosylating toxins

C The most serious disease symptoms are the direct result of toxin action

D Both organisms cause skin and respiratory tract infections

ANS:C - The most serious disease symptoms are the direct result of toxin action

No answer description is available.

Q15: Lactoferrin helps to protect against pathogens by

A sequestering Iron

B blocking sebum production

C lowering the pH

D facilitating the growth of normal flora

ANS:A - sequestering Iron

No answer description is available.

Q16: The nature of the poliovirus gives for oral vaccination (satin vaccine) as part of the eradication programme is

A heat killed virus

B live attenuated strains of all three immunological types

C small dosage of wild-type live viruses

D formalin-inactivated viruses

ANS:B - live attenuated strains of all three immunological types

No answer description is available.

Q17: In the human disease cholera, what is it that actually ends up killing the victim?

A Faulty carrier proteins

B Dehydration and loss of nutrients

C Too little water in the food stream

D
the toxin produced by the bacterium

ANS:B - Dehydration and loss of nutrients

No answer description is available.

Q18: Both Mycobacterium tuberculosis and Streptococcus pneumoniae

A are acquired by inhalation

B have cell walls that contain a high content of mycolic acids

C have polysaccharide capsules

D stay in the lung and rarely, if ever, enter the bloodstream

ANS:A - are acquired by inhalation

No answer description is available.

Q19: What is common in catheters and ventilators?

A They bypass important defenses of the body

B Bacteria responsible for associated infections are usually susceptible to antibiotics

C They predispose patients to viral rather than bacterial infections

D They are used primarily in neonatal intensive care units

ANS:A - They bypass important defenses of the body

No answer description is available.

Q20: Prontosil is

A an effective antibacterial when used in animals

B an effective antibacterial when used in in-vitro cultures

C an effective antibacterial both in animals as well as in in-vitro cultures

D not used as an antibacterial agent

ANS:C - an effective antibacterial both in animals as well as in in-vitro cultures

No answer description is available.

Q21: All infections do not cause fever and all fevers are not due to infections which of the following is an example of non-infections cause of fever?

A Typhoid

B Chicken pox

C Rheumatic disease

D Malaria

ANS:C - Rheumatic disease

No answer description is available.

Q22: Type III secretion systems are used to inject "effector" proteins directly into a host cell. Salmonella uses a type III secretion system to help the pathogen to

A survive the acid pH of the stomach

B secrete LT (heat labile toxin) and ST (heat stable toxin) into the lumen of the intestine

C survive within macrophages

D activate T cells to proliferate and secrete cytokines

ANS:C - survive within macrophages

Most of the gram negative bacteria having the needle like structure on surface which directly inject and secrete the effector proteins into host cell. The secreted proteins helps the pathogen survival and to escape from immune response.

Q23: A major difference between EHEC and EPEC is

A EHEC secretes a Shiga-like toxin and EPEC does not

B EHEC possesses a type III secretion system and EPEC does not

C EPEC rearranges host cell actin and EHEC does not

D EPEC passes through the placenta to infect the fetus and EHEC does not

ANS:A - EHEC secretes a Shiga-like toxin and EPEC does not

No answer description is available.

Q24: Plastic implants can pose a serious nosocomial infection problem because

A phagocytes have trouble moving on the plastic surface

B phagocytes have trouble engulfing bacteria embedded in a biofilm

C infected implants usually have to be surgically removed

D all of the above

ANS:D - all of the above

No answer description is available.

Q25: Mucus helps in protecting against pathogens by

A lowering the pH

B facilitating the growth of normal flora

C blocking access and attachment of pathogens to mucosal surfaces

D sequestering Iron

ANS:C - blocking access and attachment of pathogens to mucosal surfaces

No answer description is available.

Q26: Which is not a major defense mechanism in the stomach?

A Proteolytic enzymes

B Low pH

C Dense normal flora

D All of these

ANS:C - Dense normal flora

No answer description is available.

Q27: The influenza vaccine is administered each year because

A mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines

B it is a polysaccharide vaccine that does not confer long-term protection

C the vaccine is sufficiently toxic to make it necessary to administer only a small amount at any one time

D none of the above

ANS:A - mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines

No answer description is available.

Q28: Coxsackie virus B3, a subgroup of enteroviruses, commonly causes

A acute hemorrhagic conjunctivitis

B muscular dystrophy

C myocarditis

D gastroenteritis

ANS:C - myocarditis

No answer description is available.

Q29: Immunization with which of the following toxoid induces high titer serum antibody, but does not protect from the corresponding disease?

A Tetanus

B Botulism

C Diphtheria

D Shigellosis

ANS:B - Botulism

No answer description is available.

Q30: An important host defense of human beings is a dense resident microbiota associated with

A lungs

B bladder

C uterus

D vagina

ANS:D - vagina

Why not lungs?



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