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In a bacteriology lab, bacteria cultured from fecal samples produced red colonies on Endo agar. What is the most likely microorganism?
- A. Escherichia coli
- B. Salmonella
- C. Shigella
- D. Proteus vulgaris
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli typically produces red colonies on Endo agar due to its ability to ferment lactose. This results in the production of acid, causing the colonies to appear red. Salmonella and Shigella are non-lactose fermenters, so they would appear colorless or transparent on Endo agar. Proteus vulgaris is not commonly associated with red colonies on Endo agar. Therefore, based on the characteristic lactose fermentation pattern, E. coli is the most likely microorganism in this scenario.
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The main virulence factor of Neisseria meningitidis is?
- A. The polysaccharide capsule
- B. The beta lactamase
- C. The erythrogenic toxin
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host.
Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis.
Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis.
Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.
Humoral factors of the natural resistance are:
- A. Macrophages and macrophages
- B. Lysozyme, lactoferrin, interferon, complement
- C. B and T lymphocytes, NK cells
- D. Immunoglobulins A, G and M
Correct Answer: B
Rationale: The correct answer is B because lysozyme, lactoferrin, interferon, and complement are all humoral factors involved in natural resistance. Lysozyme and lactoferrin are antimicrobial proteins that help defend against pathogens. Interferon is a signaling protein that inhibits viral replication, while complement is a group of proteins that enhance the immune response by promoting inflammation and opsonization.
Choices A, C, and D are incorrect:
- Choice A mentions only macrophages, which are not humoral factors but rather phagocytic cells.
- Choice C lists immune cells involved in adaptive immunity (B and T lymphocytes, NK cells) rather than humoral factors of natural resistance.
- Choice D includes immunoglobulins, which are part of adaptive immunity, not natural resistance.
A patient with a sore throat had a throat smear revealing Gram-positive cocci in pairs with a capsule. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Neisseria meningitidis
- C. Haemophilus influenzae
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: Rationale:
1. Gram-positive cocci in pairs indicate Streptococcus pneumoniae.
2. Presence of a capsule points to S. pneumoniae as it has a polysaccharide capsule.
3. S. pneumoniae commonly causes sore throat.
4. Neisseria meningitidis, Haemophilus influenzae, and Klebsiella pneumoniae are not typically associated with sore throat.
In Transmissive infections, the vector is:
- A. Air
- B. Objects
- C. Medical devices
- D. Water
Correct Answer: A
Rationale: The correct answer is A: Air. In transmissive infections, the vector refers to the means by which the infectious agent is transmitted from one host to another. Air can carry pathogens such as viruses and bacteria, leading to respiratory infections like the flu or tuberculosis. Airborne transmission occurs when droplets containing the pathogens are inhaled. Objects (B), medical devices (C), and water (D) can also transmit infections, but they are not specifically related to transmissive infections. Objects and medical devices can harbor pathogens, while waterborne infections are transmitted through contaminated water sources. However, in the context of transmissive infections, the primary vector is the air due to its ability to carry infectious agents over distances.
A female patient consulted a doctor about a sense of epigastric discomfort, nausea and anorexia. A duodenal content analysis revealed lamblia. What drug should be prescribed?
- A. Metronidazole B.Chingamin C.Rifampicin D.Isoniazid E.Acyclovir
Correct Answer: A
Rationale: The correct answer is A: Metronidazole. Metronidazole is the drug of choice for treating Giardiasis caused by Giardia lamblia, which presents with symptoms such as epigastric discomfort, nausea, and anorexia. Metronidazole effectively targets and eliminates the parasite. Chingamin, Rifampicin, Isoniazid, and Acyclovir are not effective against Giardia lamblia and are used to treat other infections caused by different pathogens. Therefore, Metronidazole is the most appropriate choice in this scenario.