MDS PREP
In the context of tetanus, which statement is INCORRECT?
1) The primary antibody response is dominated by IgM.
2) The secondary antibody response is dominated by IgG.
3) Passive immunization is achieved through injection of tetanus antitoxin.
4) Adoptive immunization involves transfer of tetanus toxoid.
General Microbiology Answer: 4
Adoptive immunization involves the transfer of readymade immune cells, such as antibodies, from a donor to a recipient. Tetanus immunization is typically achieved through active immunization with the tetanus toxoid, which induces the body to produce its own antibodies against the tetanus toxin. Passive immunization, on the other hand, is achieved by injecting tetanus antitoxin, which provides immediate but temporary protection by neutralizing the toxin in the recipients body. The statement is incorrect because tetanus toxoid is used for active immunization, not adoptive immunization.
What is the correct color coding for bio-medical waste that requires incineration or deep burial?
1) Red
2) Yellow
3) Blue/white translucent
4) Black
General Microbiology Answer: 2
Yellow is the designated color for bio-medical waste that is considered hazardous and requires incineration or deep burial. This classification helps in the proper disposal of infectious and potentially harmful materials.
What is the significance of "Rose spots" in typhoid fever?
1) They indicate the presence of a complication such as intestinal perforation.
2) They are a diagnostic sign of typhoid fever.
3) They indicate the patient is no longer infectious.
4) They indicate the patient has developed antibodies to the bacterium.
General Microbiology Answer: 2The presence of "Rose spots" can
help in diagnosing typhoid fever, as they are relatively specific to this
illness. They typically appear in the trunk and are not a result of increased
sensitivity to the touch or pressure.
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 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.
What is the primary target of antibodies in neutralizing the action of exotoxins?
1) Cell wall components
2) Lipopolysaccharides
3) Protein components of the toxin
4) Enzymes involved in toxin production
General Microbiology Answer: 3
Antibodies neutralize exotoxins by binding to their protein components, preventing them from interacting with host cells and causing damage. This immune response is critical for protecting the host from the harmful effects of these toxins.
Selective medium for streptococcus mutans?
1 mac conkey medium
2 mitis salivarius bacitracin agar
3 neutrient agar
4 tellurite medium
Microbiology
Answer: 2
Colonies of E. coli serotype O157:H7 appear on Mac Conkey Sorbitol Agar as colourless colonies non-sorbitol fermenter. Others E. coli, sorbitol fermenters, give red colonies and gram-negative non-sorbitol fermenters appear translucent.
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.