mastering microbiology test bank

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters that are catalase-positive and coagulase-negative points towards coagulase-negative staphylococci like Staphylococcus epidermidis. Staphylococcus aureus is catalase-positive and coagulase-positive. Streptococcus pyogenes is catalase-negative. Enterococcus faecalis is catalase-negative and not typically seen in clusters. Therefore, the most likely causative agent in this scenario is Staphylococcus epidermidis.

Correct Answer: A

Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis. Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria. Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment. Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.

Correct Answer: B

Rationale: The correct answer is B: protein synthesis. Bacterial ribosomes are responsible for translating messenger RNA into proteins through a process called translation. Ribosomes are composed of both protein and RNA molecules and facilitate the binding of transfer RNA to the messenger RNA to assemble the amino acids in the correct order to form a protein. DNA replication (A) is carried out by enzymes such as DNA polymerase, not ribosomes. Cell wall synthesis (C) is a process involving enzymes that build the structure of the cell wall in bacteria. RNA splicing (D) is a eukaryotic process that involves removing introns from pre-mRNA molecules, which is not a function of bacterial ribosomes.

Correct Answer: C

Rationale: The Baltimore classification system categorizes viruses based on their genome type and replication strategy. It divides viruses into seven groups: Group I (dsDNA), Group II (ssDNA), Group III (dsRNA), Group IV (ssRNA(+)), Group V (ssRNA(-)), Group VI (ssRNA-RT), and Group VII (dsDNA-RT). Each group represents a distinct viral genome and replication method. Therefore, the correct answer is C. The other choices are incorrect because the Baltimore classification system specifically identifies viruses into seven groups, not four, five, or nine.

Correct Answer: D

Rationale: The correct answer is D: All of the above. - Streptococcus pneumoniae is a common cause of community-acquired pneumonia. - Mycobacterium tuberculosis can cause pulmonary tuberculosis, which can present as pneumonia-like symptoms. - Pseudomonas aeruginosa is an opportunistic pathogen that can cause pneumonia in immunocompromised individuals. Therefore, all three bacteria can cause pneumonia, making option D the correct choice. Options A, B, and C are incorrect because they each represent a bacterium that can cause pneumonia, so only selecting one of them would not encompass all common causes of pneumonia.