Nokea
Which bacteria produce exotoxins that damage host tissues?
- A. Clostridium tetani and Bacillus anthracis
- B. Escherichia coli and Pseudomonas aeruginosa
- C. Streptococcus pneumoniae and Listeria monocytogenes
- D. Salmonella typhi and Mycobacterium tuberculosis
Correct Answer: A
Rationale: The correct answer is A: Clostridium tetani and Bacillus anthracis. Both bacteria produce exotoxins that damage host tissues. Clostridium tetani produces tetanospasmin, which causes muscle rigidity in tetanus. Bacillus anthracis produces anthrax toxins, leading to tissue damage and systemic effects.
Explanation:
- Choice B (Escherichia coli and Pseudomonas aeruginosa) primarily cause infections through other mechanisms and do not produce exotoxins that damage host tissues.
- Choice C (Streptococcus pneumoniae and Listeria monocytogenes) are known for causing infections but not primarily through exotoxins that damage host tissues.
- Choice D (Salmonella typhi and Mycobacterium tuberculosis) cause diseases through different mechanisms and do not produce exotoxins that directly damage host tissues.
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Which of the following is a key feature of Mycobacterium tuberculosis?
- A. Produces spores
- B. Gram-negative
- C. Acid-fast cell wall
- D. Produces toxins
Correct Answer: C
Rationale: The correct answer is C: Acid-fast cell wall. Mycobacterium tuberculosis is characterized by its unique cell wall composition, containing high levels of mycolic acids which make it acid-fast. This property allows it to resist decolorization during acid-fast staining procedures. This distinguishes it from other bacteria.
A: Producing spores is not a key feature of Mycobacterium tuberculosis. Spore formation is more commonly associated with bacterial species such as Bacillus and Clostridium.
B: Mycobacterium tuberculosis is not Gram-negative. It is classified as acid-fast Gram-positive.
D: Mycobacterium tuberculosis does not produce toxins as a key feature. Its pathogenicity is more closely related to its ability to evade host immune responses and persist in host tissues.
What is the function of bacterial flagella?
- A. Protein synthesis
- B. Motility
- C. Adhesion to surfaces
- D. DNA replication
Correct Answer: B
Rationale: The correct answer is B: Motility. Bacterial flagella function in providing motility to bacteria, allowing them to move towards nutrients or away from harmful substances. Flagella are long, whip-like appendages that rotate to propel the bacteria through their environment.
Incorrect choices:
A: Protein synthesis - Bacterial flagella are not involved in protein synthesis.
C: Adhesion to surfaces - While some bacteria use flagella for attachment, their main function is not adhesion.
D: DNA replication - Flagella do not play a role in DNA replication, which occurs in the bacterial cell's nucleus.
An outbreak of food poisoning was recorded in an urban settlement. The illness was diagnosed as botulism on the grounds of clinical presentations. What foodstuffs should be chosen for analysis in the first place in order to confirm the diagnosis?
- A. Tinned food
- B. Potatoes
- C. Pasteurized milk
- D. Boiled meat
Correct Answer: A
Rationale: The correct answer is A: Tinned food. Botulism is often caused by the botulinum toxin produced by the bacterium Clostridium botulinum, which can be present in improperly canned foods. Analyzing tinned food allows for direct detection of the toxin or bacteria, confirming the diagnosis. Potatoes, pasteurized milk, and boiled meat are less likely sources of botulism compared to tinned food, making them less suitable for initial analysis in this case.
A patient with pneumonia had sputum cultured, revealing Gram-negative diplococci. The bacteria were oxidase-positive and fermentative. What is the most likely causative agent?
- A. Neisseria meningitidis
- B. Neisseria gonorrhoeae
- C. Moraxella catarrhalis
- D. Haemophilus influenzae
Correct Answer: A
Rationale: The correct answer is A: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococcus that is oxidase-positive and fermentative. Neisseria gonorrhoeae is also a Gram-negative diplococcus, but it is not fermentative. Moraxella catarrhalis is oxidase-positive but not fermentative. Haemophilus influenzae is Gram-negative but is not a diplococcus, and it is not fermentative. Therefore, based on the characteristics provided in the question, Neisseria meningitidis is the most likely causative agent.
Which bacteria are known for producing toxins that can cause severe gastrointestinal illness?
- A. Clostridium botulinum
- B. Vibrio cholerae
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, "All of the above." Clostridium botulinum produces botulinum toxin causing botulism, Vibrio cholerae produces cholera toxin leading to severe diarrhea, and certain strains of Escherichia coli produce toxins causing gastrointestinal illness. Therefore, all three bacteria are known for producing toxins that can cause severe gastrointestinal illness. Choices A, B, and C individually represent bacteria known for producing toxins that can cause severe gastrointestinal illness, making them incorrect individual choices.