Nokea
The flagellar antigen of the bacteria is known as:
- A. D antigen
- B. H antigen
- C. K antigen
- D. F antigen
Correct Answer: B
Rationale: The correct answer is B: H antigen. Flagellar antigen is typically referred to as the H antigen in bacteria. Flagella are the whip-like structures used for movement in bacteria, and the H antigen is specifically associated with the flagella. The other choices (A: D antigen, C: K antigen, D: F antigen) are not related to flagella in bacteria and are commonly associated with other types of antigens in bacterial classification.
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A patient with a deep tissue infection had Gram-negative rods isolated from the wound culture. The bacteria were oxidase-positive and non-lactose fermenters. What is the most likely causative agent?
- A. Pseudomonas aeruginosa
- B. Escherichia coli
- C. Klebsiella pneumoniae
- D. Shigella dysenteriae
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas is a Gram-negative rod, oxidase-positive, and non-lactose fermenter. These characteristics are typical of Pseudomonas species.
B: Escherichia coli is a Gram-negative rod but is lactose fermenter and usually oxidase-negative.
C: Klebsiella pneumoniae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative.
D: Shigella dysenteriae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative and is more associated with causing shigellosis rather than deep tissue infections.
Malaria is caused by a:
- A. virus
- B. bacterium
- C. helminth
- D. protozoan
Correct Answer: D
Rationale: The correct answer is D: protozoan. Malaria is caused by Plasmodium parasites transmitted through the bite of infected female Anopheles mosquitoes. These parasites belong to the protozoa kingdom, not viruses (choice A), bacteria (choice B), or helminths (choice C). Protozoa have complex life cycles involving both mosquito and human hosts, leading to the development of malaria in humans. Other choices are incorrect as they do not align with the known etiology and characteristics of malaria.
A child is ill with diphtheria. A smear of the affected mucous membrane revealed blue rods with thickenings at the poles. What staining method was used?
- A. Neisser
- B. Gram
- C. Ziehl-Neelsen
- D. Loeffler
Correct Answer: A
Rationale: The correct answer is A: Neisser staining method. Neisser staining method is used to stain diphtheria bacilli, which appear as blue rods with thickenings at the poles. The rationale is that Neisser staining specifically targets and highlights the characteristics of the diphtheria bacilli.
Incorrect choices:
B: Gram staining is not specific for diphtheria bacilli and does not show the characteristic blue rods with thickenings at the poles.
C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for diphtheria bacilli.
D: Loeffler staining is used for diphtheria bacilli but does not produce blue rods with thickenings at the poles as seen in this case.
Which of the following bacteria is known for causing dental caries (cavities)?
- A. Streptococcus mutans
- B. Streptococcus pneumoniae
- C. Bacillus anthracis
- D. Clostridium botulinum
Correct Answer: A
Rationale: Step 1: Streptococcus mutans is known for its ability to produce acids that contribute to the demineralization of tooth enamel, leading to dental caries.
Step 2: Streptococcus pneumoniae is a common cause of respiratory infections, not dental caries.
Step 3: Bacillus anthracis causes anthrax, a serious bacterial infection, not dental caries.
Step 4: Clostridium botulinum causes botulism, a severe form of food poisoning, not dental caries.
Summary: Streptococcus mutans is the correct answer as it is specifically associated with causing dental caries, while the other choices are linked to different diseases.
Which of the following statements is not correct with regard to Mycobacterium tuberculosis and/or the disease it caused?
- A. The pathogen contains mycolic acid in the cell wall
- B. The pathogen can live intracellularly in macrophages
- C. The antibodies formed are protective
- D. None of the above
Correct Answer: C
Rationale: Rationale:
C is the correct answer because antibodies formed against Mycobacterium tuberculosis are not protective. They do not efficiently clear the infection due to the bacterium's ability to evade the immune response by residing intracellularly in macrophages. Antibodies play a minimal role in controlling tuberculosis compared to cell-mediated immunity.
Summary:
A is incorrect because Mycobacterium tuberculosis does contain mycolic acid in its cell wall. B is incorrect because the pathogen can indeed live intracellularly in macrophages. D is incorrect as C is the correct answer.