Microbiology An Introduction 12th Edition Test Bank

Correct Answer: C

Rationale: The correct answer is C: Quinine. Quinine is known for its destructive effect on erythrocytic forms of malarial plasmodia and dysenteric amoebae. It is commonly used for the treatment and prevention of diseases such as malaria, amebiasis, and interstitial disease. Quinine works by interfering with the parasite's ability to break down hemoglobin in red blood cells, ultimately leading to their destruction. Incorrect choices: A: Chingamin - Chingamin is not typically used to treat malaria, amebiasis, or interstitial disease. B: Emetine hydrochloride - Emetine hydrochloride is primarily used for treating amoebic dysentery and is not commonly used for malaria treatment. D: Erythromycin - Erythromycin is an antibiotic used to treat bacterial infections, not parasitic infections like malaria or amebiasis.

Correct Answer: A

Rationale: The correct answer is A: Triatomine bug. Triatomine bugs, also known as "kissing bugs," are the specific carrier of the trypanosomes that cause Chagas disease. These bugs transmit the parasite through their feces, which contain the infectious forms of the trypanosomes. When the bug bites a human or animal, it defecates near the bite wound, allowing the parasites to enter the bloodstream through the broken skin. Mosquitoes (B) transmit diseases like malaria and dengue fever, not Chagas disease. Tsetse flies (C) are known for transmitting African trypanosomiasis (sleeping sickness), not Chagas disease. Cockroaches (D) are not known to transmit Chagas disease.

Correct Answer: B

Rationale: The correct answer is B: Coxiella burnetii. Q-fever is caused by the bacterium Coxiella burnetii. It is not caused by viruses like Bunyaviridae or Filoviridae. Rickettsia conorii causes Mediterranean spotted fever, not Q-fever. Coxiella burnetii is the only bacterium among the choices known to be the etiological agent of Q-fever.

Correct Answer: B

Rationale: The correct answer is B: Klebsiella pneumoniae. This bacterium is gram-negative, capsulated, and forms lactose-positive colonies. It was first isolated in pneumonia but is more commonly associated with urinary infections, otitis, meningitides, sepsis, and nosocomial infections. Klebsiella pneumoniae fits all the characteristics mentioned in the question, making it the correct choice. Incorrect choices: A: Staphylococcus aureus is gram-positive and does not have a capsule. C: Streptococcus pneumoniae is also gram-positive and does not fit the description given. D: Mycobacterium tuberculosis is an acid-fast bacterium associated with tuberculosis, but it is neither gram-negative nor lactose-positive.

Correct Answer: B

Rationale: The correct answer is B: Thick gram-positive non-sporeforming bacilli. In botulism, the causative agent, Clostridium botulinum, is a thick gram-positive bacilli that does not form spores. This is a key characteristic morphologic feature. A: Gram-positive spore-forming bacilli with subterminal spore - This is incorrect as Clostridium botulinum does not have subterminal spores. C: Gram-positive spore-forming bacilli with terminal spore - Incorrect because Clostridium botulinum does not form spores. D: Thin mobile spore-forming bacilli with central spore - Incorrect because Clostridium botulinum is not thin, mobile, or spore-forming. In summary, the most characteristic morphologic feature of the botulism agent is being thick, gram-positive, and non-sporeforming, making choice B the correct answer.