MDS PREP
What is the first X-linked immunodeficiency disease to have been recognized?
1) X-linked agammaglobulinemia
2) Severe combined immunodeficiency (SCID)
3) X-linked chronic granulomatous disease (CGD)
4) Wiskott-Aldrich syndrome
General Microbiology Answer: 1the first X-linked immunodeficiency disease to be recognized is X-linked agammaglobulinemia. It is a primary immunodeficiency disorder caused by a mutation in the X-chromosome-linked gene responsible for the production of antibodies (specifically, immunoglobulins), leading to a deficiency of B cells and impaired humoral immunity.
What is the characteristic appearance of Bacillus anthracis in gelatin stab culture?
1) Smooth liquefaction
2) Inverted fir tree appearance
3) No liquefaction
4) Uniform turbidity
The inverted fir tree appearance is characteristic of Bacillus anthracis in gelatin stab culture.
Which of the following is a characteristic of endotoxins that makes them distinct from exotoxins?
1) They are heat labile
2) They are actively secreted by bacterial cells
3) They are proteins
4) They are part of the bacterial cell wall
General Microbiology Answer: 4
Endotoxins are components of the outer membrane of Gram-negative bacteria and are released when the bacteria die or divide. This structural characteristic differentiates them from exotoxins, which are secreted by living bacteria.
Which of the following is a method for indirect diagnosis of tuberculosis?
1) Culture methods
2) Smear examination
3) Polymerase chain reaction
4) Latex agglutination
General Microbiology Answer: 4The polymerase chain reaction (PCR) is a molecular technique used to amplify DNA sequences. In the context of tuberculosis, PCR can be used to detect the presence of Mycobacterium tuberculosis DNA in clinical samples, making it a valuable tool for indirect diagnosis.
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.
What is the commonest subtype of Hepatitis B virus in Thailand?
1) Subtype A
2) Subtype B
3) Subtype C
4) Subtype E
General Microbiology Answer: 4
Subtype B is the most common subtype of Hepatitis B virus found in Thailand, linked to increased risks of chronic infection.
Which of the following describes the colony morphology of Bacillus anthracis on an agar plate?
1) Smooth and shiny
2) Irregularly round with a frosted glass appearance
3) Small and translucent
4) Large and mucoid
Bacillus anthracis colonies on an agar plate typically appear irregularly round with a frosted glass appearance.
What is the principle behind the Prausnitz and Kustner experiment demonstrating IgE-mediated type I hypersensitivity?
1) Injection of allergen into a non-allergic person causes an allergic reaction.
2) Transfer of serum containing allergen-specific IgE from an allergic person to a non-allergic person induces an allergic reaction.
3) Introduction of allergen-specific T cells into a non-allergic person induces an allergic reaction.
4) Exposure of a non-allergic person to high doses of an allergen induces tolerance.
General Microbiology Answer: 2the Prausnitz and Kustner experiment demonstrated Transfer of serum containing allergen-specific IgE from an allergic person to a non-allergic person induces an allergic reaction. This experiment showed that the allergic state is mediated by a serum component, which we now know is the immunoglobulin E (IgE), and that it can be passively transferred from one individual to another.