Nokea
Which staining method is used for proving the formation of spores
- A. Klett and Gins
- B. Ziehl-Neelsen
- C. Gram and Loeffler's
- D. Moeller
Correct Answer: D
Rationale: The correct answer is D: Moeller. Moeller staining method is specifically designed to detect spores due to its ability to differentiate between the spore and the vegetative cell. It involves applying multiple stains such as malachite green, safranin, and heat to visualize the endospore structure. This method is essential for proving the formation of spores as it highlights the resistant spore structures within the bacterial cell.
A: Klett and Gins is not used for spore staining.
B: Ziehl-Neelsen is used for acid-fast staining, not spore staining.
C: Gram and Loeffler's are used for gram staining, not spore staining.
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A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-positive. What is the most likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.
Transduction is:
- A. Transformation
- B. Transfer of genetic material between donor and recipient bacterial cells with the help of latent phage
- C. Transfer of large plasmids from a donor cell to a recipient cell
- D. None of the above
Correct Answer: B
Rationale: Transduction is the transfer of genetic material between bacterial cells with the help of a phage (virus). This process involves a phage infecting a bacterial cell, replicating inside it, and then transferring bacterial DNA along with phage DNA to another bacterial cell. This is different from transformation (choice A) which involves the uptake of naked DNA by a bacterial cell and plasmid transfer (choice C) which involves the transfer of small, circular DNA molecules. Therefore, the correct answer is B because it specifically describes the process of transduction in bacteria, while choices A and C describe different mechanisms of genetic transfer.
What are the two main targets currently used in anti-HIV therapy?
- A. Reverse transcriptase and something integrase
- B. Reverse transcriptase and protease
- C. Protease and integrase
- D. Viral glycoproteins gp120 and gp41
Correct Answer: B
Rationale: The correct answer is B: Reverse transcriptase and protease. Reverse transcriptase converts viral RNA into DNA, a crucial step in viral replication. Protease is responsible for cleaving viral polyproteins into functional proteins. Targeting both enzymes disrupts viral replication. Choice A is incorrect as integrase is not a main target in current therapy. Choice C is incorrect because protease is targeted along with reverse transcriptase, not integrase. Choice D is incorrect as targeting viral glycoproteins is not a main strategy in anti-HIV therapy.
A 4 year old child had Mantoux test. 60 hours after tuberculin introduction a focal skin hardening and redness 15 mm in diameter appeared. It was regarded as positive test. What type of hypersensitivity reaction is this test based upon?
- A. Delayed-type hypersensitivity
- B. Immune complex-mediated hypersensitivity
- C. Complement-mediated cytotoxic hypersensitivity
- D. Immediate hypersensitivity
Correct Answer: A
Rationale: The correct answer is A: Delayed-type hypersensitivity. The Mantoux test is a type IV hypersensitivity reaction, which is also known as delayed-type hypersensitivity. This reaction typically occurs 48-72 hours after exposure to an antigen, such as tuberculin in this case. The focal skin hardening and redness that appeared 60 hours after tuberculin introduction align with the timeline and characteristics of a delayed-type hypersensitivity reaction.
Summary:
- Choice A (Delayed-type hypersensitivity): Correct, as explained above.
- Choice B (Immune complex-mediated hypersensitivity): Incorrect, as this reaction involves immune complexes and typically presents with tissue damage and inflammation.
- Choice C (Complement-mediated cytotoxic hypersensitivity): Incorrect, as this reaction involves the activation of complement proteins leading to cell lysis.
- Choice D (Immediate hypersensitivity): Incorrect, as this reaction, such as in allergies, occurs within minutes to hours of exposure to an antigen and involves IgE-mediated mast
Specify the microbiological characteristic of the air:
- A. Contaminated
- B. Within the permissible limits
- C. Almost pure
- D. Pure
Correct Answer: A
Rationale: The correct answer is A: Contaminated. The air is never completely free of microorganisms, so it is considered contaminated. Microorganisms are ubiquitous in the environment. Permissible limits (B) imply a specific standard, which is not relevant to the general microbiological characteristic of air. Almost pure (C) and pure (D) are not accurate as air always contains some level of microorganisms.