Foundations in Microbiology Test Bank

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A 60-year-old patient was hospitalized to the surgical department because of infection caused by blue pus bacillus (Pseudomonas aeruginosa) which is sensative to penicillin antibiotics. Indicate which of the given penicillins has marked activity to the Pseudomonas aeruginosa?

  • A. Carbenicillin disodium
  • B. Benzylpenicillin
  • C. Methicillin
  • D. Oxacillin
Correct Answer: A

Rationale: The correct answer is A: Carbenicillin disodium. Carbenicillin is a semisynthetic penicillin that has marked activity against Pseudomonas aeruginosa. This is due to its extended spectrum of activity and increased stability against beta-lactamases produced by Pseudomonas aeruginosa. Carbenicillin is commonly used to treat infections caused by this bacterium.

Choice B: Benzylpenicillin (Penicillin G) has limited activity against Pseudomonas aeruginosa.
Choice C: Methicillin is not effective against Pseudomonas aeruginosa.
Choice D: Oxacillin also has limited activity against Pseudomonas aeruginosa.

In summary, Carbenicillin is the correct choice due to its marked activity against Pseudomonas aeruginosa compared to the other penicillins listed.

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For family Rhabdoviridae is true that:

  • A. They are enveloped viruses
  • B. They cause plague
  • C. They have spherical shape
  • D. They infect only humans
Correct Answer: A

Rationale: The correct answer is A: They are enveloped viruses. Rhabdoviridae family consists of enveloped viruses, which means they have a lipid envelope surrounding their protein coat. This envelope helps the virus in infecting host cells and evading the immune system. The other choices are incorrect because B: They cause plague is not true as Rhabdoviridae family typically causes diseases like rabies in mammals. C: They have spherical shape is incorrect as rhabdoviruses have a bullet-shaped structure. D: They infect only humans is also incorrect as Rhabdoviridae viruses can infect a wide range of hosts beyond just humans.

A journalist's body temperature has sharply increased in the morning three weeks after his mission in India, it was accompanied with shivering and bad headache. A few hours later the temperature decreased. The attacks began to repeat in a day. He was diagnosed with tropical malaria. What stage of development of Plasmodium is infective for anopheles-female?

  • A. Gametocytes
  • B. B.Shizontes
  • C. C.Merozoites
  • D. E.Sporozoites
Correct Answer: D

Rationale: The correct answer is D: Sporozoites. Sporozoites are the infective stage of Plasmodium for the female Anopheles mosquito. Here's the rationale: After being transmitted to a human host through a mosquito bite, the sporozoites travel to the liver where they mature and reproduce asexually as merozoites (not the infective stage for mosquitoes). The merozoites then infect red blood cells, leading to symptoms like fever, headache, and shivering. During the blood stage, some merozoites develop into male and female gametocytes, which are not infective to mosquitoes. When a mosquito bites an infected person, it ingests gametocytes, which then develop into male and female gametes and fuse to form ookinetes. Ookinetes develop into oocysts in the mosquito's gut, releasing sporozoites that migrate to the salivary glands, ready to infect a new human host when the mosquito bites

Patients planned for treatment with monoclonal antibodies are tested for:

  • A. HBV
  • B. HCV
  • C. M. tuberculosis
  • D. All are correct
Correct Answer: D

Rationale: The correct answer is D: All are correct. Patients planned for treatment with monoclonal antibodies should be tested for HBV, HCV, and M. tuberculosis due to the risk of reactivation of these infections during treatment. HBV and HCV reactivation can lead to severe liver damage, while M. tuberculosis reactivation can cause serious respiratory complications. Testing for all three infections helps in identifying and managing any pre-existing infections to ensure patient safety during monoclonal antibody treatment. Choices A, B, and C are incorrect because each of these infections presents specific risks that need to be assessed before initiating monoclonal antibody therapy.

Which of the following transport mechanisms transports water across the plasma membrane?

  • A. osmosis
  • B. facilitated diffusion
  • C. phagocytosis
  • D. exocytosis
Correct Answer: A

Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.

Which of the following organisms produces aflatoxin, a carcinogenic substance?

  • A. Candida albicans
  • B. Claviceps purpurea
  • C. Aspergillus flavus
  • D. Staphylococcus aureus
Correct Answer: C

Rationale: Step-by-step rationale:
1. Aspergillus flavus is a fungus known to produce aflatoxin.
2. Aflatoxin is a potent carcinogen found in contaminated food.
3. Candida albicans is a yeast species not associated with aflatoxin production.
4. Claviceps purpurea is a fungus that produces ergot alkaloids, not aflatoxin.
5. Staphylococcus aureus is a bacterium known for causing food poisoning, not aflatoxin production.

Summary: Aspergillus flavus is the correct answer as it is the organism known to produce aflatoxin, a carcinogenic substance. Other choices are incorrect as they are not associated with aflatoxin production.

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