Nokea
Gram-negative rods producing blue-green pigment and a fruity odor were isolated from a wound infection. What is the causative agent?
- A. Pseudomonas aeruginosa
- B. Proteus mirabilis
- C. Klebsiella pneumoniae
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is known for producing a blue-green pigment called pyocyanin, which gives a characteristic color to the colonies. The fruity odor is due to the production of a compound called 2-aminoacetophenone by P. aeruginosa. These features are classic for P. aeruginosa and help differentiate it from other Gram-negative rods. Proteus mirabilis (B) typically does not produce blue-green pigment or fruity odor. Klebsiella pneumoniae (C) and Escherichia coli (D) also do not exhibit these specific characteristics associated with P. aeruginosa.
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The organisms to be identified have a nucleus surrounded by a nuclear membrane. Genetic material is concentrated predominantly in the chromosomes which consist of DNA strands and protein molecules. These cells divide mitotically. Identify these organisms:
- A. Eukaryotes
- B. Bacteriophages
- C. Prokaryotes
- D. Viruses
Correct Answer: A
Rationale: Step-by-step rationale:
1. The presence of a nucleus with a nuclear membrane indicates eukaryotic cells.
2. Eukaryotes have genetic material in chromosomes made of DNA and proteins.
3. Mitotic division is characteristic of eukaryotic cells.
4. Therefore, the organisms described are eukaryotes.
Summary:
- Bacteriophages (B) are viruses that infect bacteria.
- Prokaryotes (C) lack a nucleus and their genetic material is not organized into chromosomes.
- Viruses (D) are not considered living organisms and do not have a nucleus or chromosomes.
After 4 months of treatment for tuberculosis the patient began complaining of toes and fingers numbness, sensation of creeps. He was diagnosed with polyneuritis. What antituberculous drug might have caused these complications?
- A. Isoniazid
- B. Rifampicin
- C. Ciprofloxacin
- D. Sodium salt of benzylpenicillin
Correct Answer: A
Rationale: The correct answer is A: Isoniazid. Isoniazid is known to cause peripheral neuropathy as a side effect, especially with prolonged use. It can lead to symptoms such as numbness, tingling, and weakness in the toes and fingers due to its neurotoxic effects. Rifampicin (B) is less likely to cause neuropathy. Ciprofloxacin (C) is not typically associated with neuropathy. Sodium salt of benzylpenicillin (D) is an antibiotic but is not known to cause polyneuritis.
The enzyme used by bacteria to break down hydrogen peroxide is:
- A. Amylase
- B. Catalase
- C. Lipase
- D. Protease
Correct Answer: B
Rationale: The correct answer is B: Catalase. Catalase is the enzyme responsible for breaking down hydrogen peroxide into water and oxygen. This process helps protect the bacteria from oxidative damage caused by hydrogen peroxide. Amylase (A), Lipase (C), and Protease (D) are enzymes that are not involved in breaking down hydrogen peroxide. Amylase is involved in breaking down starch, Lipase breaks down lipids, and Protease breaks down proteins. Therefore, they are not the correct enzymes for the given question.
All are correct except:
- A. Spotted fevers can be caused by Rickettsia mooseri and Rickettsia provazekii
- B. The Q-fever is transmitted only after ticks bite
- C. The Mediterranean fever is present with maculopapular rash
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B because Q-fever is not transmitted only after ticks bite; it can also be transmitted through inhalation of contaminated aerosols. Rickettsia mooseri and Rickettsia provazekii can cause spotted fevers, making choice A correct. Mediterranean fever is associated with a recurrent pattern of fever, not maculopapular rash, making choice C incorrect. "None of the above" is not correct in this case as choice B is incorrect.
The six generally recognized types of H. Influenzae are: a,b,c,d,e and f. They are divided on the basis of their:
- A. Vi-antigen
- B. K-antigen
- C. O-antigen
- D. H-antigen
Correct Answer: B
Rationale: The correct answer is B: K-antigen. H. Influenzae types are classified based on their capsular polysaccharides, which are known as K-antigens. The K-antigen is a major virulence factor and plays a crucial role in the pathogenicity of H. Influenzae. The other options (A, C, D) are not used to classify H. Influenzae types. Vi-antigen is related to Salmonella serotyping, O-antigen is characteristic of gram-negative bacteria such as Escherichia coli and Salmonella, and H-antigen is typically associated with flagellar antigens of bacteria like Salmonella and E. coli.