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Which of the following bacteria produce endotoxins that can lead to septic shock?
- A. Staphylococcus aureus
- B. Escherichia coli
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria listed (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) can produce endotoxins that can lead to septic shock. Endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria like E. coli and P. aeruginosa. Staphylococcus aureus, a Gram-positive bacterium, can also produce endotoxins called superantigens that can trigger a massive immune response leading to septic shock. Therefore, all of the above choices are correct. Choices A, B, and C alone are incorrect because they do not account for the fact that all three bacteria listed produce endotoxins that can cause septic shock.
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A smear of a patient's sputum suspected for tuberculosis was prepared and stained. The smear showed red bacilli against a blue background. What staining method was used?
- A. Ziehl-Neelsen
- B. Gram
- C. Giemsa
- D. Neisser
Correct Answer: A
Rationale: The correct answer is A: Ziehl-Neelsen staining method. This method is used to detect acid-fast bacteria like Mycobacterium tuberculosis. Step-by-step rationale: 1. Acid-fast bacteria resist decolorization with acid-alcohol. 2. The red bacilli seen in the smear indicate acid-fast bacteria. 3. Ziehl-Neelsen stain uses carbol fuchsin to stain acid-fast bacteria red. 4. The blue background is likely the counterstain methylene blue. Incorrect choices: B: Gram stain is for categorizing bacteria into Gram-positive or Gram-negative, not specific for acid-fast bacteria. C: Giemsa stain is used for blood films and detecting parasites, not acid-fast bacteria. D: Neisser stain is not a standard microbiological staining method.
Sanitary-biologic examination of air in a drugstore revealed a sanitary-indicative microorganism. Name it:
- A. Staphylococcus aureus
- B. Colon bacillus
- C. Fecal enterococcus
- D. α-haemolytic streptococcus
Correct Answer: C
Rationale: The correct answer is C: Fecal enterococcus. In a drugstore setting, finding a fecal-indicative microorganism like fecal enterococcus indicates a potential contamination from fecal matter, which poses a significant health risk. Staphylococcus aureus (Choice A) and α-haemolytic streptococcus (Choice D) are not typically indicative of fecal contamination. Colon bacillus (Choice B) is a common bacterium found in the gut but is not specifically indicative of fecal contamination. Therefore, choice C, fecal enterococcus, is the most appropriate microorganism indicating unsanitary conditions in a drugstore.
Which of the following is a disease caused by a protozoan?
- A. Cat scratch disease
- B. Toxoplasmosis
- C. Relapsing fever
- D. Plague
Correct Answer: B
Rationale: The correct answer is B: Toxoplasmosis. Toxoplasmosis is caused by the protozoan Toxoplasma gondii. The rationale for this is that protozoa are single-celled organisms that can cause diseases in humans. Cat scratch disease (A) is caused by a bacterium, Bartonella henselae. Relapsing fever (C) is caused by the bacterium Borrelia recurrentis. Plague (D) is caused by the bacterium Yersinia pestis. Therefore, the only choice caused by a protozoan is toxoplasmosis, making it the correct answer.
Infections of the reproductive tract resulting from the introduction of microorganisms through a medical procedure are called:
- A. chronic infections
- B. endogenous infections
- C. systemic infections
- D. iatrogenic infections
Correct Answer: D
Rationale: The correct answer is D: iatrogenic infections. Iatrogenic infections refer to infections caused by medical or surgical treatment, including procedures that introduce microorganisms into the body. In this case, infections of the reproductive tract caused by medical procedures fall under this category.
A: Chronic infections do not specifically refer to infections caused by medical procedures.
B: Endogenous infections arise from organisms already present in or on the body, not introduced through medical procedures.
C: Systemic infections affect the entire body, not specific to infections caused by medical procedures.
Therefore, the term "iatrogenic infections" is the most appropriate choice in this context.
Which enzyme is one of the most important and constant criteria for pathogenicity of staphylococcus aureus?
- A. beta lactamase
- B. plasma coagulase
- C. catalase
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: plasma coagulase. This enzyme is essential for the pathogenicity of Staphylococcus aureus as it can convert fibrinogen to fibrin, forming a protective barrier around the bacteria. This helps the bacteria evade the host's immune system. Beta lactamase (A) is not directly related to pathogenicity but rather resistance to beta-lactam antibiotics. Catalase (C) is produced by many bacteria, including Staphylococcus aureus, but it is not a specific indicator of pathogenicity. Choice D is incorrect as plasma coagulase is indeed an important criterion for the pathogenicity of Staphylococcus aureus.