Nokea
Gram-positive spore-forming bacilli were extracted in anoxic environment from the patient's wound contaminated with soil. Cultivation on a blood-glucose agar resulted in growth of the colonies surrounded with hemolysis zone. What agent was extracted from the wound?
- A. Clostridium perfringens
- B. Clostridium botulinum
- C. Staphylococcus aureus
- D. Pseudomonas aeruginosa
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is a gram-positive spore-forming bacillus commonly found in soil. It produces hemolysis on blood agar, as described in the question. Clostridium botulinum is also a gram-positive spore-forming bacillus, but it does not typically cause hemolysis. Staphylococcus aureus is a gram-positive cocci, not a bacillus. Pseudomonas aeruginosa is a gram-negative bacterium, not a gram-positive spore-forming bacillus.
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Which bacteria produce exotoxins that affect the nervous system?
- A. Clostridium botulinum and Clostridium tetani
- B. Escherichia coli and Salmonella
- C. Bacillus anthracis and Listeria monocytogenes
- D. Pseudomonas aeruginosa and Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium botulinum and Clostridium tetani. Both bacteria produce exotoxins that affect the nervous system. Clostridium botulinum produces botulinum toxin, causing botulism, leading to muscle paralysis. Clostridium tetani produces tetanospasmin, causing tetanus, leading to muscle stiffness and spasms.
Choice B (Escherichia coli and Salmonella) are known for causing gastrointestinal infections, not specifically affecting the nervous system. Choice C (Bacillus anthracis and Listeria monocytogenes) produce toxins that primarily affect other body systems, not the nervous system. Choice D (Pseudomonas aeruginosa and Staphylococcus aureus) are associated with skin and respiratory infections, not neurological effects.
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.
Which of the following bacteria is known for producing a biofilm on medical devices?
- A. Clostridium tetani
- B. Pseudomonas aeruginosa
- C. Salmonella enterica
- D. Staphylococcus aureus
Correct Answer: B
Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is known for producing biofilms on medical devices due to its ability to adhere and form a slimy layer that protects it from antibiotics and the host immune system. Pseudomonas aeruginosa is commonly associated with healthcare-associated infections.
Clostridium tetani (A) causes tetanus, not known for biofilm production on medical devices. Salmonella enterica (C) causes foodborne illnesses, not typically associated with medical device biofilms. Staphylococcus aureus (D) is a common pathogen in healthcare settings but is not specifically known for biofilm production on medical devices.
A 47-year-old patient came to see a doctor on the 7th day of disease. The disease developed very fast: after the chill body temperature rose to 40oC and lasted up to 7 hours, then dropped abruptly, which caused profuse sweat. There were three such attacks occur in once in two days. Two days ago the patient arrived from Africa. Objectively: pale skin, subicteric sclera, significantly enlarged liver and spleen. What is the cause of fever attacks in this disease?
- A. Erythrocytic schizogony
- B. Tissue schizogony
- C. Exotoxin of a causative agent
- D. Gametocytes
Correct Answer: A
Rationale: The correct answer is A: Erythrocytic schizogony. In this case, the patient most likely has malaria, specifically caused by Plasmodium falciparum. The fever attacks every 2 days (tertian fever) are characteristic of P. falciparum infection. The cycle of erythrocytic schizogony in P. falciparum is around 48 hours, leading to the recurring fever pattern. Choices B, C, and D are incorrect as tissue schizogony does not cause the characteristic fever pattern, exotoxins are not typically involved in malaria fever, and gametocytes do not directly cause fever attacks.
A child with diarrhea had stool microscopy revealing cysts with four nuclei. What is the most likely causative agent?
- A. Entamoeba histolytica
- B. Giardia lamblia
- C. Balantidium coli
- D. Trichomonas hominis
Correct Answer: A
Rationale: The correct answer is A: Entamoeba histolytica. This pathogen is known to cause amoebic dysentery, characterized by diarrhea with bloody or mucoid stools. The presence of cysts with four nuclei in the stool microscopy is a characteristic feature of Entamoeba histolytica. Other choices are incorrect because Giardia lamblia typically presents with binucleate cysts, Balantidium coli is a ciliated protozoan, and Trichomonas hominis is a non-pathogenic parasite found in the human intestine.