Nokea
The technique that combines freezing and drying to preserve microbes and other cells is
- A. desiccation.
- B. lyophilization.
- C. pasteurization.
- D. radiation.
Correct Answer: B
Rationale: The correct answer is B: lyophilization. This technique involves freezing the sample and then removing the ice through sublimation, preserving the cells in a dry state. Desiccation (A) simply involves drying without freezing. Pasteurization (C) is a heat treatment to kill pathogens, not used for preservation. Radiation (D) can sterilize but doesn't involve freezing and drying like lyophilization.
You may also like to solve these questions
A patient with an abscess had Gram-positive cocci in clusters isolated from a wound culture. The organism was catalase-positive and coagulase-positive. What is the likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step-by-step rationale:
1. Gram-positive cocci in clusters suggest Staphylococcus or Streptococcus.
2. Catalase-positive and coagulase-positive narrow it down to Staphylococcus.
3. Staphylococcus aureus is catalase-positive and coagulase-positive.
Therefore, the likely causative agent is Staphylococcus aureus.
Summary:
A: Correct - Staphylococcus aureus fits all the characteristics.
B: Incorrect - Staphylococcus epidermidis is catalase-negative and coagulase-negative.
C: Incorrect - Streptococcus pyogenes is catalase-negative and coagulase-negative.
D: Incorrect - Enterococcus faecalis is catalase-negative and coagulase-negative.
Which of the following organisms belongs in the group I category?
- A. Francisella tularensis
- B. Clostridium difficile
- C. Helicobacter pylori
- D. Bacillus anthracis
Correct Answer: C
Rationale: The correct answer is C: Helicobacter pylori. Group I organisms are classified based on their low infectious doses and potential for bioterrorism. H. pylori is known to cause gastric ulcers and is categorized as a Group I organism due to its ability to cause disease at low doses.
A: Francisella tularensis is a Group A bioterrorism agent, not Group I.
B: Clostridium difficile is not typically classified as a Group I organism.
D: Bacillus anthracis is a Group A bioterrorism agent, not Group I.
Which one is FALSE:
- A. Tissue samples and aspirations are better specimens than the swabs for diagnosis of skin and soft tissue infections
- B. To prove anaerobic agents. The specimen should be collected from the surface of the wound.
- C. The skin rash in some infections is due to the excessive production
- D. Healthy skin is an impenetrable barrier for the microorganisms
Correct Answer: B
Rationale: The correct answer is B because collecting specimens from the surface of a wound does not provide adequate samples for anaerobic agent detection. Anaerobic agents thrive in deep tissue environments with low oxygen levels, making surface specimens unreliable. Tissue samples and aspirations (choice A) are superior for diagnosing skin infections. Excessive production of toxins, not skin rash (choice C), causes symptoms in some infections. While healthy skin provides some protection, it is not completely impenetrable to microorganisms (choice D).
A patient with bacterial endocarditis had Gram-positive cocci in chains isolated from blood cultures. The organism was catalase-negative. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This is because Streptococcus pyogenes is a Gram-positive cocci in chains bacterium that is catalase-negative, making it the most likely causative agent in this scenario. Streptococcus pyogenes is a common pathogen causing bacterial endocarditis.
Summary of other choices:
B: Staphylococcus aureus is a Gram-positive cocci bacterium but is catalase-positive, so it is unlikely in this case.
C: Enterococcus faecalis is a Gram-positive cocci bacterium, but it is catalase-negative, which is not consistent with the given information.
D: Micrococcus luteus is a Gram-positive cocci bacterium but is catalase-positive, making it an unlikely causative agent.
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.