Virology Quiz Questions

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Questions and Answers

How is sterilization in an autoclave achieved?

Radiation

Dry heat

Moist heat (correct)

Filtration

What is the purpose of an antibiogram?

To assess the sensitivity of bacteria to antibiotics (correct)

To study the ability of bacteria to produce antibiotics

To examine the harmfulness of antibiotics

To measure the weight of antibiotics

How do bacteria primarily divide?

Binary fission (correct)

Mitosis

Transduction

Meiosis

What is symbiosis?

Living together in a community of two or more different organisms Signup and view all the answers

From a clinical perspective, how are bacteria classified?

Extracellular parasites Signup and view all the answers

Which of the following is true for enveloped viruses?

All icosahedral and some spherical viruses Signup and view all the answers

Viruses are primarily classified into several large groups based on:

Nucleic acid characteristics Signup and view all the answers

Viruses can be purified based on their size and density using:

Density gradient Signup and view all the answers

The most commonly used method of indirect virus counting is:

Plaque counting Signup and view all the answers

For virus isolation, embryos of the following are most commonly used:

Chickens Signup and view all the answers

Adhesion of the influenza virus to the target cell surface is enabled by the presence of:

Hemagglutinin Signup and view all the answers

In an infected cell, viruses can do everything except:

Degrade host cell DNA Signup and view all the answers

The 'holes' formed in tissue culture due to virus replication are called:

Plaques Signup and view all the answers

Which statement is not true:

Viruses replicate extracellularly Signup and view all the answers

Conquistadors conquered the Aztec Empire with the help of an epidemic of:

Smallpox Signup and view all the answers

Anthracis appears as:

clusters Signup and view all the answers

Gram-positive lancet-shaped or flame-shaped diplococci suggest a diagnosis of:

Streptococcus pneumoniae Signup and view all the answers

Choose the correct sentence:

An important criterion for diagnosing diseases caused by Enterococcus faecalis is a fourfold rise in complement-fixing antibody titer Signup and view all the answers

Swarming on agar is a cultural characteristic significant for the identification of:

Proteus sp. Signup and view all the answers

Which of the following statements about typhoid fever is correct:

after immunization with the TAB vaccine, the titer of O antibodies rises rapidly and remains elevated for several years Signup and view all the answers

Cholera enterotoxin:

causes the excretion of sodium and water into the intestinal lumen Signup and view all the answers

In a direct Gram stain preparation, how are meningococci and gonococci differentiated?

Can be differentiated Signup and view all the answers

The causative agents of bacterial vaginosis include all bacteria except:

Chlamydia trachomatis Signup and view all the answers

How long does M.tuberculosis form visible colonies on solid nutrient medium before a negative result is issued?

2-3 weeks Signup and view all the answers

The exotoxin of Corynebacterium diphtheriae is:

antigenically different and labeled with letters A, B, C, and D Signup and view all the answers

Which exoproduct is considered a virulence factor of Staphylococcus aureus?

Coagulase Signup and view all the answers

The presence of neutralizing antibodies to diphtheria toxin can be demonstrated by:

Elek test Signup and view all the answers

What type of bacterial species is Staphylococcus epidermidis?

Conditionally pathogenic Signup and view all the answers

Which selective medium is used for the isolation of Corynebacterium diphtheriae?

Tinsdale agar Signup and view all the answers

Where does E.coli most commonly cause pyogenic infections?

Urinary tract Signup and view all the answers

Which sentence is correct?

The main reservoir of group B streptococcus (Streptococcus agalactiae) is the vaginal mucosa Signup and view all the answers

Does S.typhi reproduce in macrophages?

Yes, by inhibiting the formation of phagolysosomes and oxidative bursts Signup and view all the answers

What is typhus?

A generalized infection accompanied by high fever and intoxication Signup and view all the answers

Infections with S.Arizonae are common in which group?

Patients treated in Arizona Signup and view all the answers

Is cholera toxin an AB toxin that activates adenylate cyclase?

No Signup and view all the answers

Which DNA viruses include Influenza A and hepatitis B virus?

Influenza A and hepatitis B virus Signup and view all the answers

What does not cause Gastroenteritis?

Adenoviruses Signup and view all the answers

Which infection does not result in a chronic carrier state?

None of the provided answers is correct Signup and view all the answers

Which viruses are transmitted via respiratory transmission?

Correct answers are a and c Signup and view all the answers

Which viruses have negative RNA?

Picornaviruses and rhabdoviruses Signup and view all the answers

What is true about Hepatitis C infection?

All of the provided answers are correct Signup and view all the answers

What is true about Measles virus?

Undergoes antigenic drift and antigenic shift Signup and view all the answers

Which of the following is NOT a viral zoonosis?

Rubella Signup and view all the answers

What is true about Hepatitis A?

Can be prevented by giving immunoglobulin Signup and view all the answers

What is true about Hepatitis B infection?

All of the provided answers are correct Signup and view all the answers

Which of these statements about Prions is true?

Have a long incubation period Signup and view all the answers

Which diseases are caused by 'slow viruses'?

Creutzfeldt-Jakob disease and progressive multifocal leukoencephalopathy Signup and view all the answers

What does Herpes simplex labialis NOT cause?

Genital herpes Signup and view all the answers

Which virus causes a vesicular rash?

Varicella-zoster virus Signup and view all the answers

What is true about Respiratory syncytial virus?

Can cause bronchiolitis Signup and view all the answers

During the incubation period of HIV infection, what is NOT true?

Anti-gp120 antibodies are not produced Signup and view all the answers

Study Notes

Here are the study notes:

Virus Classification

Viruses are primarily classified into several large groups based on: • Nucleic acid characteristics • Capsid symmetry • Type of host • Virus diameter

Virus Structure

Viruses have: • A protein coat (capsid) • Genetic material (either DNA or RNA) • Sometimes, a lipid envelope (enveloped viruses)
Enveloped viruses include: • Some icosahedral viruses • Some spherical viruses

Virus Replication

Viruses can replicate: • In the host's cytoplasm • In the host's nucleus
Viral RNA replicates in the host's: • Cytoplasm
Intracellular structures formed by viral replication are: • Inclusion bodies

Bacterial Cell Structure

The primary function of the capsule (as a bacterial cell envelope) is: • Protection of the bacterial cell
Bacterial cell walls are composed of: • Peptidoglycan (in Gram-positive bacteria)
The periplasmic space is located between: • The cell wall and the cytoplasmic membrane
The cytoplasmic membrane is a: • Double-layer membrane

Bacteriology

Bacteria are: • Prokaryotes
Bacteria have: • A nucleoid (no true nucleus)
The primary sterile region is: • The upper respiratory tract

Antimicrobial Agents

Antimicrobial agents are substances that: • Kill or prevent the multiplication of microorganisms in a living organism
Mechanisms of resistance include: • Enzymatic destruction or inactivation of the drug • Modification of the target enzyme • Alteration of cell wall permeability

Microbiology

Sterilization is: • The method by which all living microorganisms are killed or removed
Disinfection is: • The method by which the number of live microorganisms is reduced by killing or removing them
The minimum inhibitory concentration is: • The minimum concentration sufficient to inhibit bacterial growth### Microbiology
Bacteremia is a condition that occurs after the invasion of pathogenic microorganisms.
Septicemia is the invasion of the blood by pathogenic microorganisms.
Signs of inflammation include:
- Rubor (redness)
- Calor (heat)
- Tumor (swelling)
Adherence occurs between receptors on the surface of microorganisms and target tissue.
L-forms of bacteria:
- Are not found in nature
- Can occur in vitro conditions
- Are significant in antibiotic resistance
Pathogenicity is the ability of bacteria to damage tissue and cause disease.
Infectivity is the ability of a microorganism to establish an initial site of infection.
Bacterial resistance to antibiotics:
- Exists
- Is a result of inadequate antibiotic use
Invasiveness is the ability of a microorganism to establish an initial site of infection, proliferate, and spread.

Bacterial Structure and Function

Peptidoglycan is a chemical compound present only in bacterial cells.
Gram-positive and Gram-negative bacteria differ in terms of the composition of the cell wall.
Not all bacteria have a cell wall (e.g., Mycoplasma).
The cessation of growth in some bacteria leads to sporulation.

Toxins

Endotoxins:
- Are lipopolysaccharides
- Are highly toxic
- Are found in the cell wall of bacteria
Exotoxins:
- Are produced by bacteria
- Can cause disease
- Examples: diphtheria toxin, cholera toxin

Bacterial Diseases

Typhoid fever:
- Is caused by Salmonella typhi
- Is transmitted through contaminated water and food
- Can be diagnosed with the Widal test
Diphtheria:
- Is caused by Corynebacterium diphtheriae
- Is transmitted through respiratory droplets
- Can be diagnosed with the Elek test
Tuberculosis:
- Is caused by Mycobacterium tuberculosis
- Is transmitted through respiratory droplets
- Can be diagnosed with the tuberculin test
Cholera:
- Is caused by Vibrio cholerae
- Is transmitted through contaminated water and food
- Can be diagnosed with the cholera toxin test
Anthrax:
- Is caused by Bacillus anthracis
- Is transmitted through contact with contaminated animals or their products
- Can be diagnosed with the culture of the bacterium

Virulence Factors

Capsule:
- Is a polysaccharide structure
- Is a virulence factor
- Examples: Streptococcus pneumoniae, Haemophilus influenzae
Pilus:
- Is a protein structure
- Is involved in adherence
- Examples: E. coli, Neisseria gonorrhoeae
Endotoxin:
- Is a lipopolysaccharide structure
- Is a virulence factor
- Examples: Gram-negative bacteria
Exotoxin:
- Is a protein structure
- Is a virulence factor
- Examples: diphtheria toxin, cholera toxin

Bacterial Classification

Enterobacteriaceae:
- Includes E. coli, Salmonella, Shigella, Klebsiella
- Are Gram-negative
- Are commonly found in the gut
Staphylococcaceae:
- Includes Staphylococcus aureus, Staphylococcus epidermidis
- Are Gram-positive
- Are commonly found on the skin
Streptococcaceae:
- Includes Streptococcus pyogenes, Streptococcus pneumoniae
- Are Gram-positive
- Are commonly found in the respiratory tract
Mycobacteriaceae:
- Includes Mycobacterium tuberculosis, Mycobacterium bovis
- Are Gram-positive
- Are commonly found in the respiratory tract

Bacterial Vaccines

BCG vaccine:
- Is used to prevent tuberculosis
- Is composed of attenuated Mycobacterium bovis
- Is administered immediately after birth
Diphtheria vaccine:
- Is used to prevent diphtheria
- Is composed of inactivated Corynebacterium diphtheriae
- Is administered in childhood
Typhoid vaccine:
- Is used to prevent typhoid fever
- Is composed of inactivated Salmonella typhi
- Is administered in childhood
Anthrax vaccine:
- Is used to prevent anthrax
- Is composed of inactivated Bacillus anthracis
- Is administered in high-risk individuals### Chlamydia
Elementary bodies and reticulate bodies of chlamydia do not differ in RNA/DNA ratio, size, structure of the main protein of the cell membrane, or infectivity for the host cell.
Chlamydiae are obligate intracellular parasites.
They do not possess either DNA or RNA, but rather both nucleic acids together.

Mycoplasmas

Mycoplasmas differ from other bacteria in that they do not have cell walls.
They are part of the normal flora of the urogenital tract.

Tetanus

Tetanus toxin causes spastic paralysis of skeletal muscles.
Neonatal tetanus occurs if the mother is not properly protected against tetanus.
A typical tetanus-prone wound is a puncture wound.
Tetanus toxin is a neurotoxin.

Bacillus anthracis

Bacillus anthracis is a sporogenic bacterium of spherical shape.
It is a nonmotile bacterium.
Neisser staining of Bacillus anthracis can reveal metachromatic granules.
Anthrax can be transmitted through vectors, from domestic animals, or from wild animals.

Diphtheria

Diphtheroids can cause sepsis.
The vaccine against diphtheria is an anatoxin.
The pathogenesis of diphtheria involves the production of exotoxin, which inhibits protein synthesis.

Intestinal Bacteria

Virulence factors of intestinal bacteria include capsules, endotoxin (lipid A), and adhesins.
The normal bacterial flora of the digestive tract includes E. coli, Enterobacter sp., and Proteus sp.
The normal bacterial flora of the urogenital tract includes E. coli, Enterobacter sp., and Proteus sp.

Botulism

Botulism is caused by Clostridium botulinum.
Prevention of botulism is carried out by thermal processing of food and administration of hyperimmune gamma globulin.
Clostridium botulinum produces a powerful neurotoxin.

Pneumococcal Capsule

The pneumococcal capsule contributes to virulence by reducing the efficiency of phagocytosis.

Meningococci

Meningococcal carriage refers to the presence of N. meningitidis on the mucous membrane of the nasopharynx.
Meningococci and gonococci can be differentiated in a direct Gram stain preparation.

Mycobacteria

Mycobacteria are acid-alcohol resistant and have a slow growth rate.
They are stained with special staining using Ziehl-Neelsen stain.
Mycobacteria are cultured on Lowenstein-Jensen medium.
Tuberculin-positive individuals are resistant to tuberculosis infection.

Helicobacter pylori

Helicobacter pylori plays a role in the development of gastritis and duodenal ulcers.
It is a common cause of diarrhea.

Rickettsiae

Rickettsiae are Gram-negative bacteria.
They are transmitted through vectors, such as ticks, mites, or human body lice.

Epidemic Typhus

Epidemic typhus is transmitted through human body lice.
Rickettsiae are the causative agents of epidemic typhus.

Botulinum Toxin

Botulinum toxin is a neurotoxin that inhibits the release of acetylcholine.

Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae is transmitted to humans from domestic animals.

Coagulase

Coagulase is a virulence factor of Staphylococcus aureus.

Penicillinase

Penicillinase is a virulence factor of Staphylococcus aureus.

Enterotoxin

Enterotoxin is a virulence factor of Staphylococcus aureus.

Collagenase

Collagenase is a virulence factor of Clostridium perfringens.

Streptococci

Streptococci are catalase-negative cocci.
Group B streptococci (Streptococcus agalactiae) have a polysaccharide antigen in the cell wall that antigenically differs from the polysaccharide of group A beta-hemolytic streptococci (Streptococcus pyogenes).

Salmonellae

Salmonellae are divided into more than 2000 serotypes based on group O and type H antigens.
Gastroenteritis caused by salmonellae is transmitted by contaminated food, water, or infected animal products.

Shigellae

Shigellae move through enterocytes using a "comet tail" mechanism.
Shigellae cause bacillary dysentery.
The infectious dose of Shigellae is less than 200 bacteria.

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Description

Multiple choice questions about viruses, their classification, and purification methods. Covers topics such as enveloped viruses, capsid symmetry, and nucleic acid characteristics.