Nokea
Endotoxins are released upon:
- A. bacterial replication
- B. cell lysis of gram-negative bacteria
- C. antibody production
- D. formation of spores
Correct Answer: B
Rationale: The correct answer is B because endotoxins are part of the outer membrane of gram-negative bacteria. When these bacteria undergo cell lysis, the endotoxins are released, causing harmful effects. This process does not occur during bacterial replication (choice A), antibody production (choice C), or formation of spores (choice D). Bacterial replication involves the creation of new bacterial cells, not the release of endotoxins. Antibody production is the immune response to pathogens, not the direct cause of endotoxin release. Spores are dormant structures formed by some bacteria, which are not directly related to the release of endotoxins.
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Which bacteria is responsible for causing whooping cough?
- A. Bordetella pertussis
- B. Clostridium tetani
- C. Haemophilus influenzae
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Bordetella pertussis. This bacterium causes whooping cough by attaching to the respiratory tract and releasing toxins that lead to severe coughing fits. Clostridium tetani causes tetanus, not whooping cough. Haemophilus influenzae can cause respiratory infections but not specifically whooping cough. Staphylococcus aureus is known for causing skin infections and not respiratory diseases like whooping cough. Therefore, the presence of Bordetella pertussis and its specific mechanism of causing whooping cough makes it the correct answer.
Saprophytes are microorganisms which:
- A. Can induce typical infection
- B. Cannot induce infectious disease
- C. Can induce chronic infection
- D. Can induce mixed infection
Correct Answer: B
Rationale: The correct answer is B: Cannot induce infectious disease. Saprophytes are microorganisms that obtain nutrients from decaying organic matter and do not cause infectious diseases in humans. They play a vital role in the ecosystem by decomposing dead organisms. Choice A is incorrect because saprophytes do not cause typical infections. Choice C is incorrect because saprophytes do not cause chronic infections. Choice D is incorrect because saprophytes do not cause mixed infections involving multiple pathogens. Therefore, the correct answer is B as saprophytes do not induce infectious diseases.
A patient consulted a stomatologist about purulent inflammation of his gums. What drug will be the most effective if it is suspected that a causative agent is an anaerobe?
- A. Metronidazole
- B. Gentamicin C.Oxacillin D.Co-trimoxazole E.-
Correct Answer: A
Rationale: The correct answer is A: Metronidazole. Anaerobic bacteria are sensitive to metronidazole due to its mechanism of action targeting their DNA. Metronidazole is often the drug of choice for treating infections caused by anaerobic bacteria. Gentamicin, Oxacillin, and Co-trimoxazole are not effective against anaerobes. Gentamicin is an aminoglycoside mostly used for aerobic bacteria, Oxacillin is a beta-lactam antibiotic effective against gram-positive bacteria, and Co-trimoxazole is a combination of sulfamethoxazole and trimethoprim mainly used for urinary tract infections and some respiratory infections.
Specify the most commonly used parameters for autoclaving sterilization:
- A. 1.0 atm., 120º C, 15-20min
- B. 1.0 atm., 130º C, 10 hours
- C. 1.5 atm., 135º C, 5min
- D. 1.0 atm., 160º C, 1 hour
Correct Answer: A
Rationale: The correct answer is A because it specifies the commonly used parameters for autoclaving sterilization: 1.0 atm pressure, 120º C temperature, and 15-20 minutes duration. This combination ensures effective sterilization by providing the necessary heat and pressure for killing microorganisms.
Rationale:
1. Pressure of 1.0 atm: Standard atmospheric pressure commonly used in autoclaving.
2. Temperature of 120º C: Optimal temperature for sterilization without causing damage to heat-sensitive materials.
3. Duration of 15-20 minutes: Time required for heat and pressure to penetrate and kill microorganisms effectively.
Summary of Incorrect Choices:
B: Incorrect temperature and duration, too high and long, may damage materials.
C: Incorrect pressure and temperature, higher pressure and temperature not commonly used.
D: Incorrect temperature, too high, can damage materials, and duration is longer than necessary.
The presence of E. Coli, Klebsiella pneumoniae and Pseudomonas aeruginosa in the pharynx is
- A. Part of the normal resident flora
- B. colonization
- C. both A and B
- D. none of the listed
Correct Answer: B
Rationale: The correct answer is B: colonization. E. Coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa in the pharynx indicate colonization rather than being part of the normal resident flora. Colonization refers to the presence of these bacteria on body surfaces without causing harm. They are not considered normal flora in the pharynx but rather transient or opportunistic pathogens. Choice A is incorrect because these bacteria are not part of the normal resident flora of the pharynx. Choice C is incorrect as it implies that these bacteria are both normal flora and colonization, which is not accurate. Choice D is incorrect as there is evidence of bacterial presence, indicating colonization.