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Which bacteria produce urease enzyme to neutralize stomach acid?
- A. Salmonella typhi
- B. Escherichia coli
- C. Helicobacter pylori
- D. Shigella flexneri
Correct Answer: C
Rationale: Rationale:
1. Helicobacter pylori is known for producing urease enzyme to neutralize stomach acid.
2. Urease enzyme converts urea into ammonia, buffering the acidic pH.
3. This adaptation allows H. pylori to survive in the acidic environment of the stomach.
4. Salmonella typhi, Escherichia coli, and Shigella flexneri do not produce urease.
5. Therefore, C is the correct answer based on the unique urease-producing capability of H. pylori.
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Decontamination is defined as the
- A. killing of all microorganisms in a given area.
- B. reduction or removal of unwanted chemical or biological agents.
- C. stopping of the growth of microorganisms in a given area.
- D. removal of all vegetative organisms.
Correct Answer: B
Rationale: Decontamination is the reduction or removal of unwanted chemical or biological agents to make an area safe. This includes cleaning, disinfecting, or sterilizing to eliminate harmful substances. Choice A is incorrect as decontamination doesn't necessarily involve killing all microorganisms. Choice C is incorrect as it focuses on stopping growth, not removing existing contaminants. Choice D is incorrect as it specifically mentions vegetative organisms, which may not cover all types of contaminants that need to be removed during decontamination. Thus, the correct answer is B as it accurately describes the process of decontamination.
Which of the following viruses does not belong to family Paramyxoviridae:
- A. Measles virus
- B. Respiratory syncytial virus
- C. Mumps virus
- D. Rubella virus
Correct Answer: D
Rationale: The correct answer is D: Rubella virus. Rubella virus does not belong to the family Paramyxoviridae because it belongs to the Togaviridae family. The other choices, A (Measles virus), B (Respiratory syncytial virus), and C (Mumps virus) are all members of the Paramyxoviridae family. This classification is based on the genetic and structural characteristics of the viruses. Rubella virus is distinct in its genetic composition and replication cycle compared to the Paramyxoviridae family, making it the correct choice.
Which one of the following statements about Rickettsiae is true?
- A. They do not form spores, capsules and flagella
- B. They have slim glycocalyx layer
- C. They have bipolar fimbriae
- D. All of the above
Correct Answer: D
Rationale: Rationale:
1. Rickettsiae are obligate intracellular bacteria, hence they do not form spores, capsules, or flagella.
2. They have a slim glycocalyx layer, aiding in attachment to host cells.
3. Bipolar fimbriae are structures that help in adhesion to host cells.
Therefore, all statements (A, B, and C) are true for Rickettsiae, making option D the correct answer. Other choices are incorrect as they do not accurately describe the characteristics of Rickettsiae.
A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-positive. What is the most likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.
A sputum smear from a patient with pneumonia revealed Gram-positive diplococci with a capsule. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Klebsiella pneumoniae
- C. Neisseria meningitidis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is a common cause of pneumonia and is characterized by Gram-positive diplococci with a capsule. The presence of a capsule helps the bacterium evade the immune system and contributes to its virulence. Klebsiella pneumoniae (B) is a Gram-negative bacterium and does not typically have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus and is associated with meningitis, not pneumonia. Staphylococcus aureus (D) is a Gram-positive bacterium, but it does not typically present as diplococci with a capsule in a sputum smear from a pneumonia patient.