MDS PREP
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.
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 most efficient method of sterilization in dental practice is
1. ultraviolet radiation
2. moist heat at 121°C for 20 min
3. boiling for 20 mm
4. dry heat at 40° C for 2 hours
Microbiology
Answer: 2
The most efficient method of sterilization in dental practice is moist heat at 121°C for 20 min
What is the recommended storage condition for both recombinant and plasma-derived hepatitis B vaccines?
1) At room temperature
2) In a refrigerator
3) In a freezer
4) At 4°C to 8°C
General Microbiology Answer: 4
oth recombinant and plasma-derived hepatitis B vaccines should be stored at temperatures between 4°C and 8°C to maintain their efficacy and stability. Proper storage is crucial to ensure the vaccines remain effective when administered.
The period from disease initiation to disease detection in non-infectious disease is called -
1. Incubation period
2. Serial interval
3. Latent period
4. Lag time
Microbiology
Answer: 3
Incubation period: This term is typically used for
infectious diseases and refers to the time between exposure to the
infectious agent and the onset of symptoms.
Serial interval: This refers to the time between
successive cases in a chain of transmission, specifically in infectious
diseases.
Latent period: This is the time from the initiation of
the disease process (or exposure to a risk factor) until the disease is
detectable or until symptoms appear. In non-infectious diseases, this period
can be significant, as the disease may be developing without any noticeable
symptoms.
Lag time: This term can refer to various delays in
processes but is not specifically defined in the context of disease
initiation and detection.
What is the principle behind the oxidase test used to identify bacteria?
1) The presence of specific antigens
2) The activity of certain bacterial oxidases
3) The growth of bacteria on selective media
4) The presence of enzymes that hydrolyze certain sugars
General Microbiology Answer: 2
The oxidase test is based on the presence of cytochrome c oxidase in bacteria. This enzyme catalyzes the oxidation of certain substrates, leading to a color change in the test medium, which indicates a positive result for oxidase activity.
What is the typical stool color in bacillary dysentery?
1) Dark red
2) Bright red
3) Yellow
4) Green
General Microbiology Answer: 2Bacillary dysentery, primarily caused by Shigella species, is known for producing stool that is typically bright red in color due to the presence of blood and inflammatory cells. The intense red color is a result of the invasive nature of the bacteria, which damage the intestinal lining leading to bloody diarrhea.
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