Nokea
A patient has wound abscess. Bacteriological examination of the wound content revealed a gram- negative bacillus which forms semi-transparent mucous colonies of blue-green color with a pearlescent appearance on the beef-extract agar. Culture has a specific odor of violets or jasmine. What type of pathogen was isolated from the patient's wound?
- A. P. aeruginosa
- B. P. vulgaris
- C. S. aureus
- D. S. pyogenes
Correct Answer: A
Rationale: Step 1: Gram-negative bacillus indicates P. aeruginosa, known for causing wound infections.
Step 2: Semi-transparent mucous colonies of blue-green color with a pearlescent appearance are characteristic of P. aeruginosa.
Step 3: Specific odor of violets or jasmine is a unique feature of P. aeruginosa.
Therefore, the correct answer is A: P. aeruginosa.
Summary:
- B: P. vulgaris typically forms yellow colonies and doesn't have the characteristic odor.
- C: S. aureus forms creamy white colonies, not blue-green, and has a distinct odor.
- D: S. pyogenes forms grayish-white colonies and doesn't have the unique characteristics described.
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Microscopy of sputum revealed acid-fast bacilli stained red against a blue background using Ziehl-Neelsen staining. What disease does this finding suggest?
- A. Tuberculosis
- B. Diphtheria
- C. Pneumonia
- D. Leprosy
Correct Answer: A
Rationale: The presence of acid-fast bacilli stained red against a blue background indicates mycobacteria, specifically Mycobacterium tuberculosis in this case. Ziehl-Neelsen staining is commonly used to detect tuberculosis. Diphtheria is caused by Corynebacterium diphtheriae, which does not stain with Ziehl-Neelsen. Pneumonia is a general term for lung infections caused by various pathogens. Leprosy is caused by Mycobacterium leprae, which requires special staining methods different from Ziehl-Neelsen.
In 8 days after a surgery the patient develops tetatus. The surgeon suspects this condition to be caused by suture material contaminated by tetanus agent. The material is delivered to a bacteriological laboratory. What nutrient medium is required for primary inoculation of the suture material?
- A. Sabouraud agar
- B. Endo agar
- C. Hiss medium
- D. Kitt-Tarozzi medium
Correct Answer: D
Rationale: The correct answer is D, Kitt-Tarozzi medium. This medium is specifically designed for the isolation and cultivation of Clostridium tetani, the bacteria responsible for tetanus. The other options, Sabouraud agar, Endo agar, and Hiss medium, are not suitable for the growth of Clostridium tetani. Sabouraud agar is used for fungal cultures, Endo agar is a selective medium for enteric bacteria, and Hiss medium is used for the cultivation of anaerobic bacteria other than Clostridium tetani. Therefore, the Kitt-Tarozzi medium is the most appropriate choice for isolating and identifying the tetanus agent in this scenario.
A worker of a cattle farm consulted a surgeon about fever up to 40oC, headache, weakness. Objective examination of his back revealed hyperaemia and a dark red infiltration up to 5 cm in diameter with black bottom in the center and some pustules. What disease are these presentations typical for?
- A. Anthrax
- B. Plaque
- C. Tularemia
- D. Furuncle
Correct Answer: A
Rationale: The correct answer is A: Anthrax. The symptoms of fever, headache, weakness, and the skin lesion described (hyperemic with a dark red infiltration, black center, and pustules) are characteristic of cutaneous anthrax. The black center is known as an eschar. Anthrax is caused by the bacterium Bacillus anthracis, commonly found in cattle. Plague (choice B) typically presents with swollen lymph nodes (buboes) and is caused by Yersinia pestis. Tularemia (choice C) presents with fever, ulcer at the site of infection, and lymphadenopathy, caused by Francisella tularensis. Furuncle (choice D) is a localized skin infection typically caused by Staphylococcus aureus, presenting as a red, swollen, and painful bump.
The causative agent of the pertussis (also known as whooping cough) morphologically appears as:
- A. Gram positive bacillus
- B. Gram negative coccobacillus
- C. Long Gram-negative rod shaped bacterium
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Gram negative coccobacillus. Bordetella pertussis, the causative agent of pertussis, is a gram-negative coccobacillus. This is because it is a small, rod-shaped bacterium that appears both as a bacillus (rod-shaped) and a coccus (spherical) shape. It does not retain the crystal violet stain in the Gram staining process, indicating its negative gram nature. Choice A is incorrect because pertussis is not a gram-positive bacillus. Choice C is incorrect because pertussis is not a long gram-negative rod-shaped bacterium. Choice D is incorrect as the other options do not accurately describe the morphology of Bordetella pertussis.
Bacterial transformation involves:
- A. Transfer of plasmids through pili
- B. Uptake of naked DNA from the environment
- C. Transfer of DNA via bacteriophages
- D. Binary fission
Correct Answer: B
Rationale: The correct answer is B: Uptake of naked DNA from the environment. Bacterial transformation is a process where bacteria take up free DNA from their surroundings and incorporate it into their own genome. This process is essential for genetic recombination and the acquisition of new traits. Plasmids are small DNA molecules that can be transferred between bacteria, but not necessarily through pili. Bacteriophages are viruses that infect bacteria and transfer their DNA, but this is not the primary mechanism of bacterial transformation. Binary fission is a method of bacterial reproduction, not related to the uptake of DNA.