Microbiology Chapter 14 Test Bank

Correct Answer: A

Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is caused by the protozoan Toxoplasma gondii, which can be transmitted from mother to fetus during pregnancy leading to stillbirth and malformations. This parasite can cross the placenta and infect the fetus, causing severe complications. Leishmaniasis (B), Malaria (C), and Amebiasis (D) are not known to cause intrauterine death or malformations in the same way as Toxoplasmosis. Leishmaniasis is transmitted by sandflies, Malaria by mosquitoes, and Amebiasis by contaminated food or water.

Correct Answer: A

Rationale: The correct answer is A: Leptospira. The key features pointing to Leptospira are the presence of convoluted bacteria resembling C and S letters, which is characteristic of Leptospira species. Leptospirosis presents with fever, jaundice, haemorrhagic rash, and acute renal insufficiency. The other choices (B: Treponema, C: Spirilla, D: Borrelia) do not match the histological description or the clinical presentation of the case. Treponema is associated with syphilis, Spirilla with genus Spirochaeta, and Borrelia with Lyme disease, none of which match the given scenario.

Correct Answer: C

Rationale: The correct answer is C: Fecal enterococcus. In a drugstore setting, finding a fecal-indicative microorganism like fecal enterococcus indicates a potential contamination from fecal matter, which poses a significant health risk. Staphylococcus aureus (Choice A) and α-haemolytic streptococcus (Choice D) are not typically indicative of fecal contamination. Colon bacillus (Choice B) is a common bacterium found in the gut but is not specifically indicative of fecal contamination. Therefore, choice C, fecal enterococcus, is the most appropriate microorganism indicating unsanitary conditions in a drugstore.

Correct Answer: A

Rationale: The correct answer is A because Staphylococcus aureus can develop resistance to penicillin over time due to the production of beta-lactamase enzymes. This resistance mechanism makes it no longer susceptible to penicillin. The other choices are correct: B) S. aureus can produce beta hemolysis, C) it produces various toxins like hemolysins, leucocidins, and enterotoxins, and D) it shows a positive catalase reaction due to the presence of catalase enzyme that converts hydrogen peroxide to water and oxygen.

Correct Answer: D

Rationale: The correct answer is D: rRNA. Bacterial ribosomes consist mainly of ribosomal RNA (rRNA), which plays a crucial role in protein synthesis. Ribosomes are composed of rRNA and proteins, with rRNA being the major component. rRNA serves as the structural and catalytic component of the ribosome, aiding in the binding of mRNA and tRNA during translation. Carbohydrates (A) and lipids (B) are not primary components of ribosomes, and DNA (C) is not found in ribosomes as they are involved in storing genetic information, not in protein synthesis.