Nokea
At a bacteriological laboratory animal skins are analyzed by means of Ascoli precipitaion test. What is detected if the reaction is positive?
- A. Anthrax agent antigens
- B. Brucellosis agent
- C. Anaerobic infection toxin
- D. Plague agent
Correct Answer: A
Rationale: The Ascoli precipitation test is specifically used to detect anthrax agent antigens. The test involves mixing a patient's serum with a solution containing anthrax antigens, leading to precipitation if the antigens are present. Therefore, a positive reaction in this test indicates the presence of anthrax agent antigens. The other choices (B: Brucellosis agent, C: Anaerobic infection toxin, D: Plague agent) are incorrect because the Ascoli precipitation test is not designed to detect these specific agents or toxins.
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A child with foul-smelling diarrhea had trophozoites with two nuclei and flagella identified in stool microscopy. 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 with trophozoites having two nuclei and flagella in stool microscopy. The presence of flagella and two nuclei is characteristic of Giardia lamblia. Entamoeba histolytica (Choice B) causes amoebic dysentery with trophozoites containing ingested RBCs. Trichomonas vaginalis (Choice C) is a sexually transmitted protozoan causing vaginitis with a distinctive pear-shaped trophozoite. Balantidium coli (Choice D) is a ciliated protozoan causing diarrhea with trophozoites containing a single nucleus.
What differentiates facultative anaerobes from obligate anaerobes?
- A. Facultative anaerobes require oxygen for survival
- B. Facultative anaerobes can grow with or without oxygen
- C. Obligate anaerobes can grow with oxygen
- D. Obligate anaerobes can tolerate small amounts of oxygen
Correct Answer: B
Rationale: Facultative anaerobes can switch between aerobic and anaerobic metabolism based on oxygen availability. This flexibility enables them to grow in both oxygen-rich and oxygen-poor environments, making choice B correct. Choice A is incorrect because facultative anaerobes do not require oxygen for survival. Choice C is incorrect as obligate anaerobes cannot grow in the presence of oxygen. Choice D is incorrect because obligate anaerobes cannot tolerate any amount of oxygen.
Bacteriophages reproduce by:
- A. Division
- B. Mitosis
- C. Meiosis
- D. None of them
Correct Answer: D
Rationale: Bacteriophages are viruses that infect bacteria, not living organisms. They do not reproduce through division, mitosis, or meiosis because they lack the cellular machinery for these processes. Instead, bacteriophages replicate by inserting their genetic material into a host bacterium and hijacking its cellular machinery to produce new viral particles. Therefore, the correct answer is D - None of them. Division and mitosis involve cellular division in living organisms, while meiosis is a specialized process for sexual reproduction in eukaryotic organisms, none of which apply to bacteriophages.
Which one is true about sexually transmitted infections?
- A. An example of sexually transmitted infection is the soft chancre
- B. Entry portal is only the mucus of the urogenital tract
- C. After the syphilis infection the developed immunity is life-lasting
- D. The sexually transmitted infections are typical for developing countries with low social status and low hygiene.
Correct Answer: A
Rationale: The correct answer is A because a soft chancre is a type of sexually transmitted infection caused by the bacterium Haemophilus ducreyi. It presents as a painless ulcer on the genitals. The other choices are incorrect. B is incorrect because STIs can enter the body through various routes, not only the urogenital tract mucosa. C is incorrect because immunity to syphilis is not lifelong; reinfection is possible. D is incorrect because STIs can occur in any country regardless of social status or hygiene levels.
Which of the following statements concerning Neisseria Meningitidis is correct?
- A. Has no capsules
- B. It causes epidemic meningitis
- C. Grow on differential media
- D. Gram-positive rods
Correct Answer: B
Rationale: The correct answer is B: It causes epidemic meningitis. Neisseria Meningitidis is a bacterium that can cause meningitis, an infection of the protective membranes covering the brain and spinal cord. This bacterium is known to cause outbreaks or epidemics of meningitis, especially in crowded or close-contact settings. The other choices are incorrect because:
A: Neisseria Meningitidis does have a capsule, which helps it evade the immune system.
C: Neisseria Meningitidis grows on selective media like Thayer-Martin agar, not differential media.
D: Neisseria Meningitidis is a Gram-negative diplococcus, not a Gram-positive rod.