Nokea
Endotoxins are composed of:
- A. proteins
- B. lipopolysaccharides
- C. teichoic acid
- D. peptidoglycan
Correct Answer: B
Rationale: The correct answer is B: lipopolysaccharides. Endotoxins are part of the outer membrane of Gram-negative bacteria, consisting of lipid A, core polysaccharides, and O antigen. Lipopolysaccharides are known to induce strong immune responses and can cause septic shock. Proteins (choice A) are components of exotoxins, not endotoxins. Teichoic acid (choice C) is found in Gram-positive bacteria, not Gram-negative bacteria. Peptidoglycan (choice D) is a major component of bacterial cell walls but is not considered an endotoxin.
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Which of the following bacteria produces a toxin that inhibits protein synthesis?
- A. Shigella dysenteriae
- B. Escherichia coli
- C. Clostridium tetani
- D. Staphylococcus aureus
Correct Answer: A
Rationale: Rationale: Shigella dysenteriae produces Shiga toxin, which inhibits protein synthesis by inactivating the 60S ribosomal subunit. This disrupts the translation process, leading to cell death. Escherichia coli (choice B) does not produce a toxin that inhibits protein synthesis. Clostridium tetani (choice C) produces tetanospasmin, which affects the nervous system. Staphylococcus aureus (choice D) produces toxins that cause food poisoning but do not inhibit protein synthesis.
A patient had been provisionally diagnosed with syphilis. A laboratory assistant took the blood serum for an immunologic test based on the detection of antibodies preventing the movement of treponemas and causing their death. What reaction was used for the diagnosis?
- A. Immobilization
- B. Complement binding
- C. Agglutination
- D. Precipitation
Correct Answer: A
Rationale: The correct answer is A: Immobilization. This technique is called the Treponema pallidum immobilization (TPI) test, used to diagnose syphilis. The rationale is as follows:
1. TPI test detects antibodies that prevent the movement of treponemas, causing their death.
2. By immobilizing the treponemas, it indicates the presence of specific antibodies against syphilis.
3. This test is highly specific for syphilis diagnosis as it directly targets the causative agent.
Other choices are incorrect:
B: Complement binding - Not specific to syphilis, more commonly used for other diseases.
C: Agglutination - Detects clumping of particles, not specific to treponemas or syphilis.
D: Precipitation - Involves the formation of a solid, not directly related to treponema movement or death.
Granulomas containing lymphocytes and macrophages were detected during analysis of skin biopsy material. Among macrophages there are large cells with fat inclusions, which contain microorganisms in spheric packages (Virchow's cells). The following disease is based on the described type of hypersensitivity:
- A. Leprosy
- B. Syphilis
- C. Tuberculosis
- D. Rhinoscleroma
Correct Answer: C
Rationale: The correct answer is C: Tuberculosis. Granulomas with lymphocytes and macrophages containing Virchow's cells (large cells with fat inclusions containing microorganisms) are classic findings in tuberculosis. Leprosy (A) typically presents with granulomas but with different histopathological features. Syphilis (B) does not usually form granulomas in the skin. Rhinoscleroma (D) is a chronic bacterial infection characterized by nodular lesions but does not typically involve Virchow's cells as seen in tuberculosis.
Which of the following bacteria can cause meningitis?
- A. Neisseria meningitidis
- B. Haemophilus influenzae
- C. Streptococcus pneumoniae
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, "All of the above." Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae are all bacteria known to cause meningitis. Neisseria meningitidis is a common cause of bacterial meningitis in young adults, Haemophilus influenzae type b is a common cause in children, and Streptococcus pneumoniae is a leading cause in adults and the elderly. Therefore, all three bacteria can potentially cause meningitis depending on the age group and other factors. The other choices are incorrect because each of the bacteria listed can cause meningitis, so selecting only one of them would be incorrect.
Bacteria that require low oxygen concentrations for growth are called:
- A. Facultative anaerobes
- B. Obligate aerobes
- C. Microaerophiles
- D. Obligate anaerobes
Correct Answer: C
Rationale: The correct answer is C: Microaerophiles. These bacteria grow best in environments with low oxygen levels. They require oxygen for respiration but at lower concentrations than what is present in the atmosphere. This allows them to thrive in conditions where oxygen is limited but not completely absent.
A: Facultative anaerobes can grow in both the presence and absence of oxygen.
B: Obligate aerobes require oxygen for growth.
D: Obligate anaerobes cannot survive in the presence of oxygen and typically grow in anaerobic environments.
In summary, microaerophiles are the correct choice as they specifically thrive in low oxygen environments, distinguishing them from the other options.