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A patient with a sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes.
1. Gram-positive cocci in chains suggest streptococci.
2. Catalase-negative indicates it's not staphylococci.
3. Beta-hemolytic points towards Group A Streptococcus (S. pyogenes).
Summary:
B. Streptococcus pneumoniae is not beta-hemolytic.
C. Enterococcus faecalis is not typically chains.
D. Staphylococcus aureus is catalase-positive.
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When examining a patient with a suspicion of food toxicoinfection, a doctor on duty has detected symptoms characteristic of botulism. The patient named the meals he had eaten the day before. What is the most probable cause of infection?
- A. Homemade canned meat
- B. Custard pastry from private bakery
- C. Sour cream from local dairy factory
- D. Strawberries from suburban vegetable garden
Correct Answer: A
Rationale: The correct answer is A: Homemade canned meat. Botulism is often caused by consuming improperly canned or preserved foods, particularly meats. The spores of the Clostridium botulinum bacteria can grow in anaerobic conditions, such as those found in improperly canned foods, leading to the production of the botulinum toxin. The symptoms of botulism align with those characteristic of the patient's condition.
Explanation of why the other choices are incorrect:
B: Custard pastry from private bakery - Unlikely to be the cause of botulism as this type of food is not typically associated with the growth of Clostridium botulinum.
C: Sour cream from local dairy factory - While dairy products can sometimes be sources of foodborne illness, botulism is not commonly associated with sour cream.
D: Strawberries from suburban vegetable garden - Botulism is not typically transmitted through fresh fruits or vegetables, making this an unlikely source of infection.
Which bacteria are known for causing food poisoning due to their production of enterotoxins?
- A. Clostridium botulinum
- B. Salmonella enterica
- C. Staphylococcus aureus
- 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. Salmonella enterica can produce enterotoxins causing food poisoning. Staphylococcus aureus also produces enterotoxins leading to food poisoning. Therefore, all three options can cause food poisoning due to their production of enterotoxins.
The typical site for replication of DNA viruses is:
- A. Nucleus
- B. Cytoplasm
- C. Endoplasmic Reticulum
- D. Golgi Apparatus
Correct Answer: A
Rationale: The correct answer is A: Nucleus. DNA viruses replicate in the host cell's nucleus because they require access to the host cell's DNA replication machinery. The nucleus contains the necessary enzymes and factors for DNA replication to occur accurately. The DNA viruses need to utilize these host cell components to replicate their own genetic material.
Summary of why other choices are incorrect:
B: Cytoplasm - Cytoplasm lacks the necessary enzymes and machinery for accurate DNA replication.
C: Endoplasmic Reticulum - ER is involved in protein synthesis and processing, not DNA replication.
D: Golgi Apparatus - Golgi apparatus is responsible for processing and packaging proteins, not DNA replication.
Enriched growth media:
- A. Belong to the minimal media and inhibit the development of gram+ cocci
- B. Support the development of the target bacteria groups without suppressing the growth of other microorganisms
- C. Are intended for the cultivation of only one microbial species
- D. Support the development of target bacteria groups and suppress the development of other microorganisms
Correct Answer: B
Rationale: The correct answer is B because enriched growth media provide essential nutrients that support the growth of target bacteria groups without inhibiting the growth of other microorganisms. This allows for the selective cultivation of specific microbes while still allowing for the growth of other organisms present in the sample. Choice A is incorrect because enriched media do not belong to minimal media and do not inhibit the development of gram+ cocci. Choice C is incorrect because enriched media can support the growth of multiple microbial species. Choice D is incorrect because enriched media do not suppress the development of other microorganisms but rather provide nutrients to support their growth alongside the target bacteria groups.
Which bacteria is known for causing a disease characterized by a pseudomembrane in the throat?
- A. Clostridium tetani
- B. Bordetella pertussis
- C. Corynebacterium diphtheriae
- D. Streptococcus pyogenes
Correct Answer: C
Rationale: The correct answer is C: Corynebacterium diphtheriae. This bacterium causes diphtheria, a disease characterized by a pseudomembrane in the throat. This pseudomembrane is a result of the bacterial exotoxins causing inflammation and necrosis of the throat tissues. Clostridium tetani (A) causes tetanus, characterized by muscle stiffness, not a pseudomembrane in the throat. Bordetella pertussis (B) causes whooping cough, with symptoms of severe coughing fits but no pseudomembrane. Streptococcus pyogenes (D) causes strep throat, but does not produce a pseudomembrane.