Nokea
Viral capsomeres are composed of subunits called
- A. envelopes.
- B. protomeres.
- C. capsids.
- D. nucleoids.
Correct Answer: B
Rationale: The correct answer is B: protomeres. Viral capsomeres are the building blocks of viral capsids, which are protein coats that enclose and protect the viral genetic material. These capsomeres are made up of smaller subunits called protomeres. Envelopes (A) refer to a lipid membrane surrounding some viruses, not the subunits of capsomeres. Capsids (C) are the protein coats that capsomeres make up, not the subunits themselves. Nucleoids (D) are found in bacterial cells and refer to the region where the genetic material is located, not the subunits of viral capsomeres.
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The causative agent of the pertussis (also known as whooping cough) morphologically appears as:
- A. Gram positive bacillus
- B. Gram negative coccobacillus
- C. Long Gram-negative rod shaped bacterium
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Gram negative coccobacillus. Bordetella pertussis, the causative agent of pertussis, is a gram-negative coccobacillus. This is because it is a small, rod-shaped bacterium that appears both as a bacillus (rod-shaped) and a coccus (spherical) shape. It does not retain the crystal violet stain in the Gram staining process, indicating its negative gram nature. Choice A is incorrect because pertussis is not a gram-positive bacillus. Choice C is incorrect because pertussis is not a long gram-negative rod-shaped bacterium. Choice D is incorrect as the other options do not accurately describe the morphology of Bordetella pertussis.
A 16-year-old boy from the rural area entered the technical school. During a regular Mantoux test, it turned out that this boy had a negative reaction. What tactics should the doctor choose as the most rational in this case?
- A. Repeat the test in a month
- B. Serodiagnosis of tuberculosis
- C. Urgent isolation of the boy from his groupmates
- D. BCG vaccination
Correct Answer: D
Rationale: The correct answer is D: BCG vaccination. BCG vaccination is recommended for individuals with a negative Mantoux test result, especially in countries where tuberculosis is prevalent. This vaccination can help provide protection against tuberculosis.
Choice A is incorrect because repeating the Mantoux test in a month is unnecessary since the boy already had a negative reaction.
Choice B is incorrect as serodiagnosis of tuberculosis is not the first-line approach for diagnosis, especially in this scenario.
Choice C is incorrect because urgent isolation is not necessary based solely on the Mantoux test result. Isolation is typically reserved for individuals with active tuberculosis.
The only way to get energy in haematrophic bacteria is:
- A. Heat production
- B. Biological oxidation
- C. In biosynthetic reactions
- D. Cultivation in culture media
Correct Answer: B
Rationale: The correct answer is B: Biological oxidation. Haematrophic bacteria obtain energy through biological oxidation, where they break down organic compounds to generate ATP for cellular processes. This process involves the transfer of electrons from the substrate to an electron transport chain to produce energy. Heat production (A) is a byproduct of metabolism, not the primary way to obtain energy. In biosynthetic reactions (C), energy is utilized rather than generated. Cultivation in culture media (D) is a method of growing bacteria but does not directly provide energy. Therefore, the correct answer is B as it aligns with the metabolic process of haematrophic bacteria.
4 days after a patient received a gunshot wound of the middle third of the thigh soft tissues his condition suddenly began deteriorating. There are complaints of bursting pain in the wound; pain increases during the last 12 hours. Edema of skin and hypodermic tissue quickly grows. Body temperature is 38,2oC, heart rate is 102/min. The wound edges gape, are dull in color; the muscles, viable as of day before, now protrude into the wound, look boiled, are dull in color, have dirty-grey coating and fall apart when being held with forceps. What infection has developed in the wound?
- A. Anaerobic
- B. Aerobic gram-negative
- C. Putrid
- D. Aerobic gram-positive
Correct Answer: A
Rationale: The correct answer is A: Anaerobic infection. The sudden deterioration, bursting pain, edema, foul appearance of wound, and presence of gas are indicative of gas gangrene caused by anaerobic bacteria like Clostridium perfringens. These bacteria thrive in low oxygen environments, such as deep wound tissues. The symptoms align with the classic presentation of gas gangrene, necessitating immediate surgical intervention.
Choice B: Aerobic gram-negative, is incorrect because anaerobic bacteria, not aerobic gram-negative bacteria, are responsible for gas gangrene.
Choice C: Putrid, is incorrect as it is a general term referring to foul-smelling decay and does not specify the type of infection.
Choice D: Aerobic gram-positive, is incorrect as gas gangrene is typically caused by anaerobic bacteria, not aerobic gram-positive bacteria.
By what mechanism does MRSA achieve resistance to standard beta-lactam antibiotics?
- A. Extended spectrum beta-lactamases
- B. Penicillin efflux pump
- C. Altered peptide sequence in peptidoglycan
- D. Altered penicillin binding proteins
Correct Answer: D
Rationale: The correct answer is D: Altered penicillin binding proteins. MRSA (Methicillin-resistant Staphylococcus aureus) achieves resistance to beta-lactam antibiotics, such as penicillin, by producing altered penicillin binding proteins that have reduced affinity for these antibiotics. This alteration prevents the antibiotics from binding to their target sites on the bacterial cell wall, thus rendering them ineffective.
Choice A, extended spectrum beta-lactamases, are enzymes produced by some bacteria to break down beta-lactam antibiotics, but MRSA does not use this mechanism. Choice B, penicillin efflux pump, is a mechanism where bacteria pump out antibiotics from their cells, but this is not how MRSA develops resistance. Choice C, altered peptide sequence in peptidoglycan, does not directly relate to how MRSA resists beta-lactam antibiotics.