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A child presented with foul-smelling diarrhea. Stool microscopy revealed trophozoites with two nuclei and flagella. What is the causative agent?
- A. Giardia lamblia
- B. Entamoeba histolytica
- C. Trichomonas vaginalis
- D. Balantidium coli
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a protozoan parasite that causes foul-smelling diarrhea. The trophozoites of Giardia lamblia have two nuclei and flagella, which are characteristic features seen on stool microscopy. The presence of these specific features helps differentiate Giardia lamblia from the other options. Entamoeba histolytica (B) typically presents with one nucleus and lacks flagella. Trichomonas vaginalis (C) is a sexually transmitted parasite with a different morphology. Balantidium coli (D) is a ciliated parasite, not flagellated like Giardia lamblia.
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A persistent infection that is not lytic but productive is called a __________ infection.
- A. chronic
- B. latent
- C. slow
- D. transforming
Correct Answer: A
Rationale: The correct answer is A: chronic. A persistent infection that is not lytic but productive is characterized by ongoing viral replication without cell lysis. This type of infection is referred to as chronic, as it persists over an extended period. Latent infections involve periods of dormancy with intermittent reactivation. Slow infections typically have a prolonged incubation period before causing symptoms. Transforming infections lead to permanent alterations in host cell behavior. The key distinction for this question is the continuous viral replication without cell destruction, which aligns with the definition of a chronic infection.
The most common causative agent of bacterial meningitis are:
- A. E. Coli K1, Streptococcus group B (S. agalactiae), Listeria monocytogenes
- B. Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis
- C. Staphylococcus aureus, pseudomonas aeruginosa
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B because Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis are the most common causative agents of bacterial meningitis. Haemophilus influenzae is often seen in children, Streptococcus pneumoniae is the most common in adults, and Neisseria meningitidis is common in adolescents and young adults.
Choice A is incorrect because although Streptococcus group B and Listeria monocytogenes can cause meningitis, E. Coli K1 is not a common causative agent. Choice C is incorrect because Staphylococcus aureus and Pseudomonas aeruginosa are not typically associated with bacterial meningitis. Choice D is incorrect as there are known causative agents for bacterial meningitis.
Resident microflora is found in
- A. blood
- B. lung
- C. urethra
- D. cerebro-spinal fluid
Correct Answer: C
Rationale: The correct answer is C: urethra. Resident microflora refers to the normal, beneficial bacteria that inhabit a specific area of the body without causing harm. The urethra is one of the locations where resident microflora are commonly found. These bacteria play a vital role in maintaining a healthy balance and preventing harmful pathogens from colonizing the urethra. Blood (A), lung (B), and cerebro-spinal fluid (D) are not typical locations for resident microflora as these areas are usually sterile or have very limited microbial presence to prevent infections.
Which bacteria produce endotoxins that can cause septic shock?
- A. Escherichia coli
- B. Salmonella enterica
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D. Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa all produce endotoxins that can lead to septic shock. Endotoxins are part of the outer membrane of Gram-negative bacteria and can trigger a systemic inflammatory response if released into the bloodstream. E. coli and Salmonella are common causes of bacterial infections that can lead to septic shock, while P. aeruginosa is a known opportunistic pathogen that can produce endotoxins. Therefore, all three bacteria can cause septic shock by releasing endotoxins. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that contribute to the development of septic shock.
A child 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. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive cocci in pairs with a capsule is characteristic of Streptococcus pneumoniae.
Step 1: Gram-positive cocci in pairs indicate a Streptococcus species.
Step 2: The presence of a capsule suggests S. pneumoniae specifically.
Summary:
B: Staphylococcus aureus is a Gram-positive cocci but does not typically present in pairs with a capsule.
C: Neisseria gonorrhoeae is a Gram-negative diplococcus, not a Gram-positive cocci.
D: Klebsiella pneumoniae is a Gram-negative rod, not a cocci.