Nokea
Which of the following bacteria is known for causing Lyme disease?
- A. Borrelia burgdorferi
- B. Clostridium difficile
- C. Streptococcus pneumoniae
- D. Mycobacterium tuberculosis
Correct Answer: A
Rationale: The correct answer is A: Borrelia burgdorferi. This bacterium is known for causing Lyme disease, which is transmitted through tick bites. Borrelia burgdorferi is specifically associated with Lyme disease due to its ability to infect and spread within the body, leading to a range of symptoms if left untreated.
Summary of incorrect choices:
B: Clostridium difficile - Known for causing gastrointestinal infections, not Lyme disease.
C: Streptococcus pneumoniae - Commonly causes pneumonia and other respiratory infections, not Lyme disease.
D: Mycobacterium tuberculosis - Causes tuberculosis, a respiratory disease, not Lyme disease.
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A patient with abdominal pain had a stool culture revealing non-lactose-fermenting, Gram-negative rods that produced gas in a nutrient broth. What is the most likely causative agent?
- A. Salmonella typhi
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: D
Rationale: The correct answer is D: Proteus vulgaris. This is because Proteus species are non-lactose-fermenting Gram-negative rods that are known to produce gas in nutrient broths. Proteus vulgaris is commonly associated with urinary tract infections and can also cause abdominal infections.
A: Salmonella typhi typically causes typhoid fever and is not known to produce gas in nutrient broths.
B: Shigella dysenteriae is a causative agent of dysentery and does not typically produce gas in nutrient broths.
C: Escherichia coli is a lactose-fermenting bacterium and does not fit the description of the organism in the stool culture.
The generation time of Escherichia coli is
- A. 20 min
- B. 60 min
- C. 20 hours
- D. 24 hours
Correct Answer: A
Rationale: The correct answer is A (20 min) because Escherichia coli typically has a generation time of around 20 minutes, meaning the time it takes for a bacterial population to double. This rapid reproduction rate is a key characteristic of E. coli. Option B (60 min) is incorrect as it is longer than the usual generation time. Option C (20 hours) is too long for E. coli's generation time. Option D (24 hours) is also incorrect as it is much longer than the typical generation time of E. coli.
A patient presents with diarrhea and dehydration. A fecal smear stained by Gram's method revealed Gram-negative, comma-shaped bacteria. What is the causative agent?
- A. Vibrio cholerae
- B. Salmonella typhi
- C. Shigella dysenteriae
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. Vibrio cholerae is the causative agent of cholera, which presents with severe watery diarrhea leading to dehydration. The characteristic comma-shaped (curved rod) appearance of Gram-negative bacteria is typical of Vibrio cholerae. This bacterium produces the cholera toxin, leading to the excessive secretion of fluid into the intestines. Salmonella typhi causes typhoid fever with symptoms like sustained fever, not watery diarrhea. Shigella dysenteriae causes bloody diarrhea and abdominal cramps. Escherichia coli can cause various types of infections, but typically not severe watery diarrhea like cholera.
Which of the following bacteria is known for producing a neurotoxin that causes paralysis?
- A. Clostridium botulinum
- B. Clostridium perfringens
- C. Escherichia coli
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum. This bacterium produces the botulinum neurotoxin, which causes paralysis by blocking the release of acetylcholine at neuromuscular junctions. Clostridium perfringens causes gas gangrene, not paralysis. Escherichia coli is associated with gastrointestinal infections, not paralysis. Staphylococcus aureus produces enterotoxins causing food poisoning, not paralysis. Therefore, Clostridium botulinum is the correct choice based on its well-known association with paralysis due to botulinum neurotoxin production.
Which one is true for the bacterial cell?
- A. The oxidative phosphorylation takes place in the mitochondria
- B. Capsules are essential organelles
- C. Has only DNA but not RNA
- D. Multiplies by binary fission
Correct Answer: D
Rationale: The correct answer is D: Multiplies by binary fission. Bacterial cells reproduce through binary fission, where a single cell divides into two identical daughter cells. This process is essential for bacterial growth and multiplication.
A: The oxidative phosphorylation does not take place in the mitochondria of bacterial cells but in the cell membrane.
B: Capsules are not organelles but outer protective layers found in some bacterial cells.
C: Bacterial cells contain both DNA and RNA, essential for their genetic information and protein synthesis.