MDS PREP
The bacterial population in the gingival sulcus or the pocket that influences the course of periodontal disease has been found to involve
1 bacteria indigenous to the oral cavity
2. essentially a pure culture
3. essentially the same organisms found in the healthy sulcus
4. mostly aerobic bacteria
Microbiology
Answer: 3
The bacterial population in the gingival sulcus or the pocket that influences the course of periodontal disease has essentially the same organisms found in the healthy sulcus
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 primary mechanism of action of the PCR test in diagnosing HIV infection?
1) Amplification of viral RNA or DNA
2) Detection of specific antibodies to HIV
3) Detection of the HIV virus directly
4) Measurement of the immune response to the virus
General Microbiology Answer: 1
The primary mechanism of action of the PCR test in diagnosing HIV infection is the amplification of viral RNA or DNA, allowing for the detection of the virus.
What is the typical color of Salmonella colonies on MacConkey agar, except for Sh. Sonnei?
1) Colorless
2) Pink
3) Red
4) Yellow
General Microbiology Answer: 1Salmonella species, excluding Shigella sonnei, which is lactose non-fermenting, will ferment lactose in MacConkey agar, turning the colonies pink due to the formation of acidic end-products
What reaction is tested by adding concentrated sulfuric acid to a 24-hour peptone water culture?
1) Indole reaction
2) Cholera red reaction
3) Nitrate reduction
4) Coproantibody reaction
General Microbiology Answer: 2The reaction tested by adding concentrated sulfuric acid to a 24-hour peptone water culture is Cholera red reaction, This reaction tests for the presence of cholera vibrios, which produce hydrogen sulfide gas when their culture is acidified with sulfuric acid. The gas reacts with the ferric chloride present in the medium to produce a characteristic red color.
Which of the following is a feature of the immune response involving HLA class I antigens?
1) They activate B cells
2) They present antigens to CD4+ T cells
3) They are involved in graft rejection
4) They are only present in the thymus
General Microbiology Answer: 3HLA (Human Leukocyte Antigen) class I antigens are crucial in the immune response to infections and also play a significant role in graft rejection. They present antigens to CD8+ T cells (cytotoxic T cells), which then target and destroy infected or foreign cells. While they do not directly activate B cells or CD4+ T cells, they are involved in the recognition of cells by the adaptive immune system and thus are important in the overall immune response.
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 name of the live oral vaccine for typhoid fever and what is its mechanism of action?
1) Typhoral, a Gal E mutant of S. typhi that "self-destructs" after a few cell divisions
2) CholeraVax, a killed whole-cell vaccine
3) Salmonellosis vaccine, a live attenuated strain of S. paratyphi
4) Shigellosis vaccine, a bacteriophage preparation
General Microbiology Answer: 1the live oral vaccine for typhoid fever is Typhoralx, which is a Gal E mutant of S. typhi. The mechanism of action involves the attenuated bacteria colonizing the intestinal mucosa and inducing an immune response that protects against subsequent infection with the pathogenic strain.