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The bacteria that produces a thick pseudomembrane in the throat is:
- A. Corynebacterium diphtheriae
- B. Streptococcus pyogenes
- C. Neisseria meningitidis
- D. Bacillus cereus
Correct Answer: A
Rationale: Rationale:
1. Corynebacterium diphtheriae is the correct answer as it is the bacteria responsible for causing diphtheria, characterized by a thick pseudomembrane in the throat.
2. Streptococcus pyogenes causes strep throat but does not produce a pseudomembrane.
3. Neisseria meningitidis causes meningitis and septicemia, not a throat pseudomembrane.
4. Bacillus cereus causes food poisoning, not throat-related symptoms.
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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.
A patient with a long history of chronic gastritis undergoes a gastroscopy, which detects an ulcer in the duodenum area. Microscopic examination of the tissue biopsy developed Gram-negative curved bacteria and the rapid urease activity test of the biopsy material was highly positive. The most likely cause of the disease is:
- A. Vibrio cholerae
- B. Campylobacter fetus
- C. Acinetobacter baumannii
- D. Helicobacter pylori
Correct Answer: D
Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.
A patient has food poisoning. Laboratory analysis revealed a culture of anaerobic gram-positive spore-forming bacteria. What is the most likely kind of the isolated causative agent?
- A. C. perfringens
- B. Proteus vulgaris
- C. P. mirabilis
- D. Vibrio parahemolyticus
Correct Answer: A
Rationale: The correct answer is A: C. perfringens. This is because Clostridium perfringens is a gram-positive, anaerobic, spore-forming bacterium commonly associated with food poisoning. It produces toxins that cause gastrointestinal symptoms. Proteus vulgaris (B) and P. mirabilis (C) are gram-negative bacteria not typically associated with food poisoning. Vibrio parahemolyticus (D) is a gram-negative bacterium causing seafood-related gastroenteritis, not spore-forming or anaerobic.
The enzyme used by bacteria to break down hydrogen peroxide is:
- A. Amylase
- B. Catalase
- C. Lipase
- D. Protease
Correct Answer: B
Rationale: The correct answer is B: Catalase. Catalase is the enzyme responsible for breaking down hydrogen peroxide into water and oxygen. This process helps protect the bacteria from oxidative damage caused by hydrogen peroxide. Amylase (A), Lipase (C), and Protease (D) are enzymes that are not involved in breaking down hydrogen peroxide. Amylase is involved in breaking down starch, Lipase breaks down lipids, and Protease breaks down proteins. Therefore, they are not the correct enzymes for the given question.
Ionizing radiation involves all of the following except
- A. UV light
- B. Gamma rays
- C. Electron beams
- D. X-rays
Correct Answer: A
Rationale: Ionizing radiation has enough energy to remove tightly bound electrons from atoms, creating charged particles (ions). UV light does not have enough energy to ionize atoms, making choice A the correct answer. Gamma rays, electron beams, and X-rays all have sufficient energy to cause ionization. Gamma rays are very high-energy electromagnetic radiation, electron beams are streams of high-energy electrons, and X-rays are high-energy electromagnetic radiation as well.