MDS PREP
Which of the following statements is true regarding Bacillus anthracis?
1) It is motile.
2) It is capsulated.
3) It grows in short chains.
4) It is susceptible to chloral hydrate.
Bacillus anthracis is capsulated, which is a key feature of its virulence.
Which of the following is a distinguishing feature of orthomyxoviruses?
1) Single linear RNA
2) 80-120 nm in size
3) Hemolysin present
4) Cytoplasmic replication
General Microbiology Answer: 2Orthomyxoviruses, which include the influenza viruses, are characterized by their single-stranded RNA genome. This feature distinguishes them from other virus families that may have different types of genetic material. Orthomyxoviruses are distinguished by their single linear RNA genome, which is essential for their replication and pathogenicity.
What is the role of the Vi antigen in the pathogenesis of typhoid fever?
1) It aids in colonization of the intestinal mucosa.
2) It confers resistance to antibiotics.
3) It is involved in the production of toxins.
4) It allows the bacteria to evade the host's immune response by inhibiting phagocytosis.
General Microbiology Answer: 4The role of the Vi antigen in the pathogenesis of typhoid fever is it allows the bacteria to evade the hosts immune response by inhibiting phagocytosis: The Vi antigen is a polysaccharide capsule found in some strains of S. typhi that helps the bacteria avoid phagocytosis by host immune cells. This contributes to the bacterias ability to survive and proliferate within the human body.
Which of the following bacteriophage types of diphtheria bacilli are associated with avirulent strains?
1) Type I and II
2) Type IV and VI
3) Type III
4) Type VII
Type VII bacteriophage types of diphtheria bacilli are associated with avirulent strains.
The destruction of microorganisms on living tissues, as long as there is contact between the tissues and the antimicrobial agent, denotes
1. sterilization
2. antisepsis
3. sanitization
4. none of the above
Microbiology
Answer: 2
The destruction of microorganisms on living tissues, as long as there is contact between the tissues and the antimicrobial agent, denotes antisepsis (option 2). Antisepsis refers to the application of antimicrobial agents to living tissues to reduce the possibility of infection, sepsis, or putrefaction.
Sterilization:
This is the process of completely eliminating all forms of microbial
life, including bacteria, viruses, fungi, and spores, from an object or
surface. Sterilization is typically achieved through methods such as
autoclaving (steam under pressure), dry heat, chemical sterilants, or
radiation. Sterilization is used for medical instruments, laboratory
equipment, and other items that must be free of all microorganisms.
Antisepsis:
Antisepsis refers to the application of antimicrobial agents to
living tissues to reduce the risk of infection, sepsis, or putrefaction.
Antiseptics are used on skin and mucous membranes to prevent infection
during surgical procedures, wound care, and other medical interventions.
Common antiseptics include alcohol, iodine solutions, and chlorhexidine.
Sanitization:
Sanitization is the process of reducing the number of microorganisms
on surfaces or objects to a level considered safe by public health
standards. This does not necessarily eliminate all microorganisms but
reduces them to a level that minimizes the risk of infection or disease.
Sanitization is commonly used in food service, public restrooms, and
other environments where hygiene is important.
Which of the following is a feature of HLA class I antigens?
1) Found on red blood cells
2) Involved in humoral immunity
3) Present on all nucleated cells
4) Only present in lymphocytes
HLA class I antigens are present on all nucleated cells, playing a crucial role in the immune response.
What disease is associated with inhalation of dust from infected wool?
1) Cutaneous anthrax
2) Pulmonary anthrax
3) Gastrointestinal anthrax
4) None of the above
Pulmonary anthrax is associated with inhalation of dust from infected wool.
Example Test for type IV hypersensitivity:
1) Coagulase test
2) Mantoux test
3) Schick test
4) Elek’s test
Microbiology Answer: 2
A classic example of delayed type IV hypersensitivity is the Mantoux tuberculin test in which skin induration indicates exposure to tuberculosis.
This reaction is called "delayed hypersensitivity" because it is mediated by sensitized CD4+ T lymphocytes which process antigens in association with class II HLA molecules and release lymphokines.
The lymphokines promote a reaction (especially mediated through macrophages) beginning in hours but reaching a peak in 2 to 3 days.
Hypersensitivity reactions with this mode of action include:
Granulomatous diseases (mycobacteria, fungi)
Tuberculin skin reactions
Transplant rejection
Contact dermatitis
Cytotoxic T lymphocyte (CTL) mediated responses: CD8+ T cells are generated and lyse specific cells. Class I HLA molecules play a role. Reactions with this mode include:
Neoplastic cell lysis
Transplant rejection
Virus-infected cell lysis