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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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When growing in artificial media, the number of bacteria increases in geometric progression via:
- A. Logarithmic phase
- B. Death (decline) phase
- C. Stationary phase
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Logarithmic phase. During this phase, bacteria multiply exponentially due to abundant nutrients and favorable conditions. The growth is rapid and follows a geometric progression. In contrast, the Death phase (choice B) occurs when nutrients are depleted, leading to a decline in bacterial numbers. The Stationary phase (choice C) is when growth equals death rates, resulting in a stable population size. Choice D is incorrect because the Logarithmic phase accurately describes the exponential growth pattern of bacteria in artificial media.
A patient was admitted to the hospital on the 7th day of the disease with complaints of high temperature, headache, pain in the muscles, especially in calf muscles. Dermal integuments and scleras are icteric. There is hemorrhagic rash on the skin. Urine is bloody. The patient was fishing two weeks ago. What is the most likely diagnosis?
- A. Leptospirosis
- B. Yersiniosis
- C. Salmonellosis
- D. Brucellosis
Correct Answer: A
Rationale: The most likely diagnosis is A: Leptospirosis. Leptospirosis is caused by the spirochete Leptospira interrogans and is commonly transmitted through contact with water contaminated by animal urine, such as in this case of fishing. The symptoms described match those of leptospirosis, including high fever, headache, muscle pain, jaundice, hemorrhagic rash, and bloody urine. The calf muscle pain is a characteristic symptom of leptospirosis known as "Weil's disease." Yersiniosis (B) typically presents with abdominal symptoms, Salmonellosis (C) with gastrointestinal symptoms, and Brucellosis (D) with flu-like symptoms. Therefore, based on the symptoms and history provided, Leptospirosis is the most likely diagnosis.
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.
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.
Which bacteria is known for causing the disease tetanus?
- A. Clostridium tetani
- B. Clostridium perfringens
- C. Neisseria gonorrhoeae
- D. Bacillus anthracis
Correct Answer: A
Rationale: Step-by-step rationale for why A is correct:
1. Clostridium tetani is known to produce tetanus toxin.
2. The tetanus toxin causes muscle rigidity and spasms characteristic of tetanus.
3. Clostridium perfringens is associated with gas gangrene, not tetanus.
4. Neisseria gonorrhoeae causes gonorrhea, not tetanus.
5. Bacillus anthracis causes anthrax, not tetanus.
In summary, Clostridium tetani is the correct answer as it is specifically associated with causing tetanus, while the other choices are associated with different diseases.