Nokea
Poxviruses are DNA viruses that replicate in the Cytoplasm
- A. TRUE
- B. FALSE
- C. Both answers can be correct depending on the given situation
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: TRUE. Poxviruses are indeed DNA viruses that replicate in the cytoplasm. This is due to their complex structure that allows them to carry out their replication process in the cytoplasm of the host cell. Other choices are incorrect because poxviruses specifically replicate in the cytoplasm and do not require the nucleus for replication, ruling out choice B. Choice C is incorrect because poxviruses consistently replicate in the cytoplasm regardless of the situation. Choice D is incorrect as the correct answer is A.
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Microscopic examination of a smear from a chancre revealed spiral microorganisms. The bacteria were thin and mobile with 8-12 regular coils. What is the likely diagnosis?
- A. Syphilis
- B. Leptospirosis
- C. Lyme disease
- D. Relapsing fever
Correct Answer: A
Rationale: The correct diagnosis is A: Syphilis. The spiral microorganisms described are characteristic of Treponema pallidum, the causative agent of syphilis. The thin and mobile bacteria with 8-12 regular coils match the morphology of Treponema pallidum. Leptospirosis is caused by Leptospira interrogans, which are thicker and have hook-like ends, different from the described bacteria. Lyme disease is caused by Borrelia burgdorferi, which has a different appearance than the thin, coiled bacteria in the smear. Relapsing fever is caused by Borrelia recurrentis, which typically have irregular coils, unlike the regular coils seen in the smear.
Elementary and reticular bodies are morphological?
- A. Mycoplasma genitalium
- B. Chlamydia trachomatis
- C. Rickettsia prowazekii
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Chlamydia trachomatis. Elementary bodies (EBs) and reticular bodies (RBs) are two distinct forms of Chlamydia trachomatis, a bacterium causing various infections. EBs are the infectious form, while RBs are the replicative form within host cells. Mycoplasma genitalium (choice A) lacks a cell wall and does not have these specific morphological forms. Rickettsia prowazekii (choice C) is an obligate intracellular bacterium but does not exhibit the elementary and reticular body forms characteristic of Chlamydia trachomatis. Therefore, the correct answer is B, as only Chlamydia trachomatis exhibits the elementary and reticular bodies.
All statements about plasmids are correct except:
- A. Many plasmids contain genes that confer resistance to one or more antibiotics
- B. Are smaller, circular, extrachromosomal DNAs
- C. Plasmids encode essential bacteria properties
- D. Plasmids are responsible for the bacterial conjugation
Correct Answer: C
Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.
Gram-negative rods producing blue-green pigment and a fruity odor were isolated from a wound infection. What is the causative agent?
- A. Pseudomonas aeruginosa
- B. Proteus mirabilis
- C. Klebsiella pneumoniae
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is known for producing a blue-green pigment called pyocyanin, which gives a characteristic color to the colonies. The fruity odor is due to the production of a compound called 2-aminoacetophenone by P. aeruginosa. These features are classic for P. aeruginosa and help differentiate it from other Gram-negative rods. Proteus mirabilis (B) typically does not produce blue-green pigment or fruity odor. Klebsiella pneumoniae (C) and Escherichia coli (D) also do not exhibit these specific characteristics associated with P. aeruginosa.
Erysipelas is a bacterial infection characterised by well-defined areas of bright-red, inflamed and rough or leathery skin. Which one is the causative agent:
- A. Pseudomonas aeruginosa
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Candida albicans
Correct Answer: C
Rationale: Step-by-step rationale for Choice C (Streptococcus pyogenes) being the correct answer:
1. Erysipelas is a skin infection characterized by well-defined red, inflamed skin areas.
2. Streptococcus pyogenes is a common causative agent of erysipelas.
3. This bacterium produces enzymes that break down skin proteins, leading to the characteristic symptoms of erysipelas.
4. Streptococcus pyogenes is known for causing skin infections, including erysipelas.
Summary of why the other choices are incorrect:
A. Pseudomonas aeruginosa: Typically causes opportunistic infections, but not commonly associated with erysipelas.
B. Staphylococcus aureus: Can cause skin infections, but not typically associated with erysipelas.
D. Candida albicans: Fungal infection, not a bacterium, and not known to cause erysipelas.