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A smear of sputum from the patient with suspected lobar pneumonia was stained with the use of the following stains and reagents: solution of gentian violet, Lugol's solution, 96o alcohol, water-magenta. What staining method was applied in this case?

  • A. Gram
  • B. Ziehl-Nielsen
  • C. Romanovsky
  • D. Neisser
Correct Answer: A

Rationale: The correct answer is A: Gram staining method. This method involves staining with gentian violet, followed by Lugol's solution, 96% alcohol decolorization, and counterstaining with safranin or water-magenta. This staining sequence allows for the differentiation of bacteria based on their cell wall composition. In the case of lobar pneumonia, the causative agent is typically a bacterium with a cell wall that retains the crystal violet stain after decolorization with alcohol, indicating a Gram-positive bacterium.

Summary of Incorrect Choices:
B: Ziehl-Nielsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for lobar pneumonia.
C: Romanovsky staining is primarily used in the identification of blood cells and blood parasites, not for bacteria.
D: Neisser staining is not a commonly used staining method in microbiology for bacterial identification.

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Which of the following is not considered to be a vehicle transmission?

  • A. Airborne
  • B. Insect
  • C. Foodborne
  • D. Bodily fluid
Correct Answer: B

Rationale: The correct answer is B: Insect. A vehicle transmission refers to the mode by which a disease spreads from one host to another. Insects can transmit diseases, making them a vehicle for transmission. Airborne, foodborne, and bodily fluid transmissions are well-known modes of disease spread, while insects are also known vectors for diseases like malaria and Zika.

A patient with acute food poisoning had fecal cultures grown on Endo agar, resulting in colorless colonies. What microorganism is most likely responsible?

  • A. Salmonella
  • B. Escherichia coli
  • C. Staphylococcus
  • D. Shigella
Correct Answer: A

Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria.
Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation.
Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar.
Step 4: Therefore, the correct answer is A: Salmonella.
Summary:
B: Escherichia coli ferments lactose, producing pink colonies on Endo agar.
C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar.
D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.

A 47-year-old male patient consulted a dentist about difficult mouth opening (lockjaw or trismus). The patient has a history of a stab wound of the lower extremity. What infection can be manifested by these symptoms?

  • A. Tetanus
  • B. Brucellosis
  • C. Whooping cough
  • D. Anaerobic wound infection
Correct Answer: A

Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, commonly found in soil, dust, and animal feces. The patient's history of a stab wound increases the risk of tetanus infection as the bacterium can enter the body through the wound. Tetanus infection can lead to symptoms such as lockjaw or trismus, which are characterized by muscle stiffness and difficulty opening the mouth. This is due to the neurotoxin produced by Clostridium tetani affecting the muscles.

Summary of incorrect choices:
B: Brucellosis is a bacterial infection transmitted from animals to humans through consumption of unpasteurized dairy products. It does not typically manifest with symptoms of lockjaw.
C: Whooping cough (Pertussis) is a respiratory infection caused by Bordetella pertussis bacteria. It presents with severe coughing fits but does not cause lockjaw.
D: Anaerobic wound infection

The optimal PH for most pathogenic bacteria and viruses is:

  • A. 5.0-5.5
  • B. 8.0-9.6
  • C. 7.2-7.4
  • D. 4.2-4.4
Correct Answer: C

Rationale: The correct answer is C (7.2-7.4) because most pathogenic bacteria and viruses thrive in a neutral pH environment close to 7.0. This pH range is optimal for their growth and survival. Choice A (5.0-5.5) is too acidic for most pathogens. Choice B (8.0-9.6) is too alkaline, which is not conducive for their survival. Choice D (4.2-4.4) is also too acidic and would likely inhibit the growth of pathogenic bacteria and viruses. Thus, a pH range of 7.2-7.4 provides the most suitable conditions for their proliferation.

Specify the most commonly used parameters for autoclaving sterilization:

  • A. 1.0 atm., 120º C, 15-20min
  • B. 1.0 atm., 130º C, 10 hours
  • C. 1.5 atm., 135º C, 5min
  • D. 1.0 atm., 160º C, 1 hour
Correct Answer: A

Rationale: The correct answer is A because it specifies the commonly used parameters for autoclaving sterilization: 1.0 atm pressure, 120º C temperature, and 15-20 minutes duration. This combination ensures effective sterilization by providing the necessary heat and pressure for killing microorganisms.

Rationale:
1. Pressure of 1.0 atm: Standard atmospheric pressure commonly used in autoclaving.
2. Temperature of 120º C: Optimal temperature for sterilization without causing damage to heat-sensitive materials.
3. Duration of 15-20 minutes: Time required for heat and pressure to penetrate and kill microorganisms effectively.

Summary of Incorrect Choices:
B: Incorrect temperature and duration, too high and long, may damage materials.
C: Incorrect pressure and temperature, higher pressure and temperature not commonly used.
D: Incorrect temperature, too high, can damage materials, and duration is longer than necessary.

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