MDS PREP
The main tool for detection of "cases" of tuberculosis is -
1. Sputum examination
2. Mantoux test
3. Chest X-ray
4. All of the above
Microbiology
Answer: 1
The main tool for the detection of "cases" of tuberculosis is 1.
Sputum examination.
Explanation of Each Option:
Sputum examination: This is the primary method for
diagnosing active pulmonary tuberculosis. Sputum samples are collected and
examined for the presence of Mycobacterium tuberculosis through
microscopy (e.g., acid-fast bacilli staining) and culture methods. It is
considered the gold standard for confirming active TB cases.
Mantoux test: Also known as the tuberculin skin test,
this test is used to determine if a person has been exposed to the
tuberculosis bacteria. However, it does not diagnose active TB; rather, it
indicates whether a person has been infected with the bacteria at some
point.
Chest X-ray: While chest X-rays are important for
identifying lung abnormalities associated with tuberculosis and can support
the diagnosis, they are not definitive for detecting the bacteria itself.
They are often used in conjunction with sputum examination.
The chemical nature of bacterial exotoxins is, a
1. low molecular weight polypeptide
2. lipopolysaccharide complex
3. protein
4. complex carbohydrate
Microbiology
Answer: 2
The chemical nature of bacterial exotoxins is, a
lipopolysaccharide complex
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 diameter of prions?
1) 2-4 nm
2) 4-6 nm
3) 10-12 nm
4) 20-25 nm
General Microbiology Answer: 2Prions are extremely small infectious agents, typically measuring between 4 to 6 nanometers in diameter. Their small size contributes to their ability to evade the immune system and resist conventional sterilization methods.
Two important factors for initiation of caries by oral streptococci are
1 production of glucosyl transferase and synthesis of insoluble dextran
2. production of acid and production or protease
3. production of collagenase and pro- duct ion of hyaluronidase
4. fermentation of mannitol and sorbitol and production of protease.
Microbiology
Answer: 1
Two important factors for initiation of caries by oral streptococci are production of glucosyl transferase and synthesis of insoluble dextran
The biologic standard used to test the efficiency of sterilization involves the use of
1. spores of Clostridium tetani
2. streptococcus pneumoniae
3 spores of a harmless bacillus
4. infectious hepatitis virus
Microbiology
Answer: 3
The biologic standard used to test the efficiency of sterilization typically
involves the use of spores of a harmless bacillus. This method is widely
recognized in the scientific community and is based on the principle that if a
sterilization process can effectively destroy the most heat-resistant
microorganisms, it is assumed to be capable of killing all other less resistant
microbes.
The choice of using spores of a harmless bacillus is rooted in the fact that
bacterial spores are the most heat-resistant forms of microbial life. Spores are
metabolically inactive, which makes them very hardy and capable of surviving in
adverse environmental conditions for extended periods. For sterilization
validation, scientists often employ a biological indicator that contains spores
of a known heat-resistant bacterium, such as Geobacillus stearothermophilus
(formerly Bacillus stearothermophilus) or Bacillus subtilis. These organisms are
chosen because they have well-characterized resistance profiles, and their
destruction indicates that the sterilization process has achieved the necessary
lethality to eradicate all microbial life forms, including vegetative bacteria,
fungi, and viruses.
Let's examine the other options provided:
1. Spores of Clostridium tetani: While C. tetani is a spore-forming bacterium,
its spores are not commonly used as a biological indicator for sterilization
efficiency. C. tetani is a pathogen that causes tetanus, a serious disease.
However, it is not typically used for this purpose because there are safer and
more universally accepted biological indicators available.
2. Streptococcus pneumoniae: S. pneumoniae is a bacterium that can cause
pneumonia and other infections, but it is not a spore-former. Moreover, it is
generally less resistant to heat and sterilization methods compared to
spore-forming bacteria. Thus, it is not suitable as a standard for testing
sterilization efficiency.
3. Spores of a harmless bacillus: As previously mentioned, this is the most
appropriate choice for a biologic standard in sterilization testing. These
spores serve as reliable and safe indicators of sterilization efficacy because
they mimic the resistance of pathogenic spores without posing the actual risk of
infection.
4. Infectious hepatitis virus: While viruses can be highly resistant to some
sterilization methods, they are generally more sensitive to heat than bacterial
spores. Moreover, using infectious viruses as biological indicators poses
significant biosafety risks and is not a standard practice in routine
sterilization testing. For viral resistance testing, specific viruses or
virus-like particles may be used, but these are not typically employed as the
primary biological indicators for sterilization validation due to the complexity
and high containment requirements of such testing.
Which of the following is a characteristic of amoebic dysentery?
1) More than 10 motions a day
2) Small, odorless stools
3) Dark red, copious stools
4) Presence of Charcot-Leyden crystals
Amoebic dysentery is characterized by more than 10 motions a day and the presence of Charcot-Leyden crystals.
Which of the following is NOT a type of C1. Perfringens that can cause food poisoning?
1) C1. Perfringens type A
2) C1. Perfringens type B
3) C1. Perfringens type C
4) C1. Perfringens type D
General Microbiology Answer: 4
C1. Perfringens types A, B, and C are capable of producing toxins that cause food poisoning. Type D, however, is not associated with foodborne illness. It is primarily involved in diseases such as gas gangrene and other infections due to the production of different types of toxins.