Nokea
The role of adhesins in gram positive bacteria is carried out by:
- A. Lipoteichoic acids
- B. Fimbriae
- C. Flagella
- D. Short chain mycolic chains
Correct Answer: A
Rationale: Adhesins in gram positive bacteria are typically carried out by surface structures such as lipoteichoic acids. These molecules help the bacteria adhere to host cells or tissues. Lipoteichoic acids are specific to gram positive bacteria and play a crucial role in initiating infections. Fimbriae, flagella, and short chain mycolic acids are not primarily responsible for adhesion in gram positive bacteria. Fimbriae are more commonly found in gram negative bacteria, flagella are involved in motility, and short chain mycolic acids are specific to mycobacteria. Therefore, the correct answer is A, lipoteichoic acids.
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For serological diagnostics of the whooping cough it was made large-scale reaction with parapertussis and pertussis diagnosticums. At the bottom of the test-tubes with diagnosticum of Bordetella parapertussis grain-like sediment formed. What antibodies have this reaction revealed?
- A. Bacteriolysins
- B. Precipitins
- C. Antitoxins
- D. Opsonins
Correct Answer: B
Rationale: Rationale:
1. The grain-like sediment indicates a precipitation reaction.
2. Precipitins are antibodies that cause precipitation reactions.
3. In serological diagnostics, precipitation reactions are used to detect specific antibodies.
4. Therefore, the reaction revealed in this scenario is due to the presence of precipitins.
Summary:
A: Bacteriolysins - These antibodies cause bacterial lysis, not precipitation.
C: Antitoxins - These antibodies neutralize toxins, not involved in precipitation reactions.
D: Opsonins - These antibodies enhance phagocytosis, not related to precipitation reactions.
During the skill-building session in microbiology the students need to stain the prepared and fixed sputum smears obtained from a tuberculosis patient. What staining technique should be used in this case?
- A. Gram
- B. Giemsa
- C. Ziehl-Neelsen
- D. Burri
Correct Answer: C
Rationale: The correct staining technique for sputum smears obtained from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses carbol fuchsin dye to stain the acid-fast bacteria, such as Mycobacterium tuberculosis, red. Here's a step-by-step rationale:
1. Ziehl-Neelsen staining is specifically designed to detect acid-fast bacteria like Mycobacterium tuberculosis.
2. Carbol fuchsin dye is used to penetrate the mycolic acid layer in the cell wall of the bacteria, making them resistant to decolorization.
3. Acid-alcohol is used as a decolorizer to remove the stain from non-acid-fast bacteria.
4. Methylene blue is used as a counterstain to visualize non-acid-fast bacteria in blue.
Therefore, Ziehl-Neelsen staining is the most appropriate technique for identifying Mycobacterium tuberculosis in sputum smears.
Other choices like Gram, Giemsa, and
The main function of siderophores in bacteria is:
- A. to enhance antibiotic resistance
- B. to sequester iron from the environment
- C. to form capsules
- D. to perform oxidative phosphorylation
Correct Answer: B
Rationale: The correct answer is B: to sequester iron from the environment. Siderophores are molecules produced by bacteria to chelate and acquire iron, an essential nutrient for their growth and survival. By sequestering iron, bacteria can compete with host cells and other microbes for this vital resource. This enhances their ability to thrive and establish infections. Choices A, C, and D are incorrect because siderophores do not directly enhance antibiotic resistance, form capsules, or perform oxidative phosphorylation. These functions are unrelated to the primary role of siderophores in iron acquisition.
A 43-year-old cattle farm worker is brought to the surgeon with fever, malaise, and inflamed lesions on his hands and arms. He reports that about 2 weeks before his presentation at the hospital he noticed small, painless, pruritic papules that quickly enlarged and developed a central vesicle. The vesicles developed into erosion and left painless necrotic ulcers with black, depressed eschar. Gram's staining of the ulcer reveals gram-positive spore-forming bacilli. Which of the following diseases is the most likely cause of these findings?
- A. Anthrax
- B. Chickenpox
- C. Syphilis
- D. Tularemia
Correct Answer: A
Rationale: The correct answer is A: Anthrax. The clinical presentation of painless necrotic ulcers with black eschar, along with the gram-positive spore-forming bacilli seen on Gram's staining, is classic for cutaneous anthrax. Anthrax is caused by Bacillus anthracis, which produces spores and can lead to skin lesions in individuals working with animals or animal products. Choice B, Chickenpox, typically presents with vesicular rash all over the body. Choice C, Syphilis, is caused by Treponema pallidum and does not present with the characteristic eschar seen in the patient. Choice D, Tularemia, caused by Francisella tularensis, presents with ulceroglandular lesions but lacks the black eschar characteristic of anthrax.
A patient with fever and enlarged lymph nodes had a blood smear examined under the microscope. Spiral microorganisms with pointed ends were detected. What is the likely diagnosis?
- A. Syphilis
- B. Leptospirosis
- C. Lyme disease
- D. Relapsing fever
Correct Answer: A
Rationale: Rationale: The correct answer is A: Syphilis. Spiral microorganisms with pointed ends are characteristic of Treponema pallidum, the causative agent of syphilis. This bacterium is known for its corkscrew shape. Other choices are incorrect because Leptospirosis, Lyme disease, and Relapsing fever are caused by different pathogens and do not exhibit spiral microorganisms on blood smears. Syphilis should be suspected in the presence of these specific spiral microorganisms.