Nokea
Giardiasis is a waterborne gastrointestinal disease caused by Giardia intestinalis, which is a:
- A. protozoan
- B. bacterium
- C. fungus
- D. virus
Correct Answer: A
Rationale: Step 1: Giardiasis is caused by Giardia intestinalis, which is a well-known protozoan parasite.
Step 2: Protozoans are single-celled eukaryotic organisms commonly found in water sources.
Step 3: Giardia intestinalis infects the intestine, causing symptoms like diarrhea and abdominal cramps.
Step 4: Bacteria (Choice B) are prokaryotic organisms, different from protozoans.
Step 5: Fungi (Choice C) are also eukaryotic but are not responsible for causing Giardiasis.
Step 6: Viruses (Choice D) are not cellular and cannot independently cause Giardiasis.
In summary, the correct answer is A (protozoan) because Giardia intestinalis is a protozoan parasite specifically known to cause Giardiasis, while the other choices (Bacterium, Fungus, Virus) do not match the characteristics of the
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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.
The nucleocapsid of viruses consists of
- A. genome and envelop
- B. genome and capsid
- C. capsid and spikes
- D. capsid and envelop
Correct Answer: B
Rationale: The correct answer is B because the nucleocapsid of viruses is composed of the genome (genetic material) and the capsid (protein coat). The genome contains the viral genetic information, while the capsid protects the genome and helps in viral attachment and entry into host cells.
Choice A is incorrect because the envelope is not part of the nucleocapsid but surrounds the capsid in some viruses. Choice C is incorrect as spikes are surface proteins on the viral envelope, not part of the nucleocapsid. Choice D is also incorrect because the envelope is external to the capsid and genome in many viruses.
A patient with pulmonary tuberculosis is prescribed the most effective antituberculosis antibiotic. Name this drug:
- A. Tetracycline
- B. Furasolidone
- C. Rifampicin
- D. Bactrim (Co-trimoxazole)
Correct Answer: C
Rationale: Rifampicin is the correct answer because it is a first-line antibiotic for treating pulmonary tuberculosis. It has excellent bactericidal activity and penetrates well into lung tissues where the infection is located. Rifampicin is also known for preventing the development of resistance. Tetracycline (A) and Furasolidone (B) are not commonly used for tuberculosis treatment. Bactrim (D) is a combination of sulfamethoxazole and trimethoprim, not effective for tuberculosis treatment.
Which of the following bacteria are capable of producing an exotoxin that causes severe diarrhea?
- A. Clostridium botulinum
- B. Vibrio cholerae
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria mentioned (Clostridium botulinum, Vibrio cholerae, and Escherichia coli) are capable of producing exotoxins that cause severe diarrhea. Clostridium botulinum produces botulinum toxin leading to botulism, Vibrio cholerae produces cholera toxin causing cholera, and some strains of Escherichia coli produce enterotoxins causing severe diarrhea. Choices A, B, and C alone are incorrect because each of them can produce exotoxins that cause severe diarrhea.
Which of the following best describes the role of bacterial plasmids?
- A. Regulation of bacterial growth
- B. Carrying antibiotic resistance genes
- C. Producing toxins
- D. Facilitating endospore formation
Correct Answer: B
Rationale: The correct answer is B: Carrying antibiotic resistance genes. Bacterial plasmids are small, circular DNA molecules that can carry genes, including those for antibiotic resistance. This allows bacteria to survive exposure to antibiotics. Plasmids do not directly regulate bacterial growth (A), produce toxins (C), or facilitate endospore formation (D). Plasmids play a crucial role in the spread of antibiotic resistance among bacteria.