Nokea
In which of the following especially dangerous infections, the respiratory tract is not damaged:
- A. Tularemia
- B. Plague
- C. Anthrax
- D. Cholera
Correct Answer: D
Rationale: The correct answer is D, Cholera. Cholera is caused by the bacterium Vibrio cholerae and primarily affects the intestines, leading to severe watery diarrhea and dehydration. It does not damage the respiratory tract.
Choice A, Tularemia, affects the respiratory tract and other organs. Choice B, Plague, can cause respiratory symptoms like cough and difficulty breathing. Choice C, Anthrax, can affect the respiratory tract if inhaled in its spore form.
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Which of the following is likely to be the most frequently used portal of entry for pathogens?
- A. Skin
- B. Gastrointestinal tract
- C. Respiratory tract
- D. Conjunctiva
Correct Answer: C
Rationale: The correct answer is C: Respiratory tract. The respiratory tract is likely the most frequently used portal of entry for pathogens because it is constantly exposed to the external environment and has a large surface area lined with mucous membranes that can trap and facilitate the entry of pathogens. Additionally, the respiratory tract serves as a direct pathway for pathogens to reach the bloodstream and other organs. Skin (choice A) is a physical barrier that can prevent pathogen entry, while the gastrointestinal tract (choice B) has acidic pH and enzymes that can kill many pathogens. Conjunctiva (choice D) is a less common portal of entry compared to the respiratory tract due to its smaller surface area and protective mechanisms such as tears.
Botulism agent causes severe food toxicoinfection. Point out the most characteristic morphologic feature of botulism agent.
- A. Gram-positive spore-forming bacilli with subterminal spore
- B. Thick gram-positive non-sporeforming bacilli
- C. Gram-positive spore-forming bacilli with terminal spore
- D. Thin mobile spore-forming bacilli with central spore
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.
Bacteria that use organic compounds as the source of both carbon and energy are referred to as:
- A. photoautotrophs
- B. chemoautotrophs
- C. photoheterotrophs
- D. chemoheterotrophs
Correct Answer: D
Rationale: The correct answer is D: chemoheterotrophs. Chemoheterotrophs use organic compounds as both their carbon source and energy source. They obtain energy by breaking down organic molecules through cellular respiration. Photoautotrophs (A) use light energy to produce organic compounds, chemoautotrophs (B) use inorganic compounds for energy, and photoheterotrophs (C) use light energy but require organic compounds as a carbon source. Therefore, chemoheterotrophs best describe bacteria that obtain both carbon and energy from organic compounds.
A patient with fever, enlarged lymph nodes, and bacteremia was diagnosed with plague. The Gram-stained smear revealed bipolar-staining, Gram-negative rods. What is the causative agent?
- A. Yersinia pestis
- B. Francisella tularensis
- C. Brucella abortus
- D. Clostridium botulinum
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is the causative agent of plague, characterized by fever, enlarged lymph nodes, and bacteremia. The bipolar-staining, Gram-negative rods seen on Gram stain are typical of Y. pestis.
Incorrect choices:
B: Francisella tularensis causes tularemia, not plague.
C: Brucella abortus causes brucellosis, not plague.
D: Clostridium botulinum causes botulism, not plague.
In summary, the key features of the patient's presentation and the Gram stain findings align with Yersinia pestis as the correct causative agent of plague.
The immunity in syphilis is:
- A. Nonsterile (infectious)
- B. Antitoxic
- C. Humoral
- D. A + B + C
Correct Answer: A
Rationale: The correct answer is A because immunity in syphilis is nonsterile, meaning that individuals who have been infected may still carry the bacteria and be capable of transmitting the disease. This is due to the ability of the bacterium causing syphilis, Treponema pallidum, to evade the immune system by hiding within host cells.
Option B, antitoxic, is incorrect because syphilis is not caused by a toxin produced by the bacteria, but rather by the bacterium itself.
Option C, humoral, is also incorrect as syphilis immunity involves both humoral (antibody-mediated) and cell-mediated immune responses, not solely humoral immunity.
Option D is incorrect as it includes all three options, whereas in reality, the immunity in syphilis is primarily nonsterile.