What is the role of coagulase in bacteria like Staphylococcus aureus?

Correct Answer: C

Rationale: The correct answer is C because coagulase helps bacteria like Staphylococcus aureus to form clots, allowing them to evade the host immune response. This mechanism helps the bacteria to hide from the immune system and establish infection. A. Adhesion to surfaces is usually facilitated by other factors like adhesins. B. Breaking down red blood cells is not a function of coagulase. D. Antibiotic resistance is typically mediated by other mechanisms like efflux pumps or enzymatic inactivation, not coagulase.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters, along with being catalase-positive and coagulase-negative, is indicative of Staphylococcus species. Staphylococcus epidermidis is commonly found on the skin, making it likely to cause wound infections. Summary: B: Staphylococcus aureus is catalase-positive and coagulase-positive. C: Streptococcus pyogenes is catalase-negative. D: Enterococcus faecalis is catalase-negative.

Correct Answer: C

Rationale: Rationale for Correct Answer (C - Immunity): 1. Immunity refers to the body's ability to defend against foreign agents. 2. Homeostasis is the state of steady internal conditions, not specifically related to defense. 3. Infection is the invasion and multiplication of pathogens, not the overall defense mechanism. 4. Commensalism is a symbiotic relationship where one organism benefits without harming the other.

Correct Answer: C

Rationale: Step 1: Actinomycotic granules are colonies of actinomycetes located in purulent secretions. Step 2: Actinomycosis is a disease caused by actinomycetes forming these granules. Step 3: Actinomycotic granules are typically found in tissue exudates or pus. Step 4: Therefore, choice C is correct as it accurately describes actinomycotic granules. Summary: Choice A is incorrect because actinomycotic granules are not a form of actinomycosis itself, but a characteristic of the disease. Choice B is incorrect as actinomycotic granules are not an additional outer membrane but rather colonies of actinomycetes. Choice D is incorrect as actinomycotic granules are not intracellular inclusions but extracellular colonies found in purulent secretions.

Correct Answer: D

Rationale: The correct answer is D because all three choices, Clostridium botulinum, Morbillivirus morbillorum, and Clostridium tetani, can cause infections of the CNS. Clostridium botulinum can lead to botulism, affecting the nervous system. Morbillivirus morbillorum can cause measles, which can lead to encephalitis. Clostridium tetani can cause tetanus, affecting the central nervous system. Therefore, all three choices can cause infections of the CNS. Choices A, B, and C are incorrect individually because each pathogen can cause CNS infections.

Correct Answer: C

Rationale: The correct answer is C: Candida albicans. Candida albicans is a common fungal organism that causes diaper rash in infants due to its ability to thrive in warm, moist environments. It can overgrow in the diaper area, leading to irritation and inflammation. Sporothrix schenckii (A) is a fungus that causes skin infections, but not typically diaper rash. Actinomyces (B) is a bacterium that is not commonly associated with diaper rash. Malassezia furfur (D) is a yeast that causes conditions like dandruff and seborrheic dermatitis, but not diaper rash in infants.

Correct Answer: C

Rationale: The correct answer is C: Reaction haemagglutination inhibition. This method is used to detect antibodies against influenza viruses by measuring the ability of the patient's serum to inhibit haemagglutination. This is a specific and sensitive technique for detecting influenza antibodies. A: Agglutination reaction is not specific for influenza viruses and may give false positives. B: Precipitation reaction in agar gel is not typically used for detecting influenza antibodies. D: Ration haemagglutination is not a standard method for detecting influenza antibodies.

Correct Answer: A

Rationale: Step 1: Clostridia of tetanus, botulism, anaerobic gas infection are spore-forming bacteria. Step 2: Spores are resistant structures that allow bacteria to survive in harsh conditions. Step 3: Feces contain these spore-forming bacteria due to contamination. Step 4: When feces are deposited on soil, the spores of these bacteria enter the soil. Step 5: Spores can remain dormant in soil for long periods. Summary: Choice A is correct as spore-forming bacteria enter soil through feces, which act as a source of contamination. Choices B, C, and D are incorrect as they do not involve the direct introduction of spores into soil like feces do.

Correct Answer: D

Rationale: Rationale: 1. Mycobacterium tuberculosis, Legionella pneumophila, Brucella melitensis can evade complete phagocytosis. 2. Mycobacterium tuberculosis inhibits phagosome-lysosome fusion. 3. Legionella pneumophila can prevent phagosome maturation. 4. Brucella melitensis can survive and replicate within phagocytes. 5. A + B + C together represent non-complete phagocytosis. Summary: - A, B, C individually cause incomplete phagocytosis. - Only when all three are present together (D) is non-complete phagocytosis observed.