MDS PREP
What is the outcome of a positive oxidase test for neisseria colonies?
1) Deep purple coloration
2) Yellow coloration
3) No color change
4) Green coloration
A positive oxidase test for Neisseria colonies results in a deep purple coloration.
What is the primary mode of action of exotoxins?
1) Enzymatic
2) Non-enzymatic
3) Structural disruption
4) Inhibition of protein synthesis
General Microbiology Answer: 1
The primary mode of action of exotoxins is enzymatic, as they often act as enzymes that modify or damage host cell functions.
Dry heat sterilization of paper points without incineration is accomplished at
1. 160°C for 2hours
2. 120°C for l hour
3. 100°C for 2 hours
4. 200°C for 1 hour
Microbiology
Answer: 1
Dry heat sterilization of paper points without incineration is accomplished at 160°C for 2hours
What does one unit of antitoxin refer to in the context of diphtheria toxin?
1) The amount needed to neutralize 100 MLD of toxin
2) The amount of antitoxin that causes the toxin to flocculate
3) The amount that confers immunity to an individual
4) The amount of toxin that can cause disease in an average host
One unit of antitoxin refers to the amount needed to neutralize 100 MLD of diphtheria toxin.
Which of the following is a characteristic microscopic feature of amoebic dysentery that distinguishes it from bacillary dysentery?
1) Presence of RBCs in the stool
2) Presence of pus cells in the stool
3) Presence of Charcot-Leyden crystals
4) Presence of ghost cells
General Microbiology Answer: 3
Amoebic dysentery, caused by the protozoan parasite Entamoeba histolytica, is characterized by the presence of ghost cells in the stool. Ghost cells are the remnants of red blood cells that have been phagocytosed by the amoeba. These cells are ingested and their cytoplasm is removed, leaving only the cell membrane, which gives them a "ghost-like" appearance under the microscope. This feature helps distinguish amoebic dysentery from bacillary dysentery, which is caused by bacteria such as Shigella species. Bacillary dysentery typically shows the presence of white blood cells (pus cells) and red blood cells in the stool, but not ghost cells.
What type of antibodies are known as "coproantibodies"?
1) IgA
2) IgM
3) IgG
4) Antibodies found in feces
General Microbiology Answer: 4Copro antibodies are antibodies found in feces These are typically IgA antibodies that are produced in response to infections in the gastrointestinal tract, including typhoid fever. They can be detected in stool samples and are used in diagnostic tests.
Which of the following is true about the fermentation characteristics of Bacillus anthracis?
1) Ferments salicin
2) Produces H2S abundantly
3) Ferments glucose, maltose, lactose, and sucrose
4) All of the above
Bacillus anthracis ferments glucose, maltose, lactose, and sucrose, but does not ferment salicin or produce H2S abundantly.
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.