Nokea
The following spore-forming bacteria can be preserved in soil over a long period of time: clostridia of tetanus, botulism, anaerobic gas infection. Name the way with which these microorganisms get into soil.
- A. With feces
- B. With urine
- C. With water
- D. With industrial waters
Correct Answer: A
Rationale: Step 1: Clostridia of tetanus, botulism, anaerobic gas infection are spore-forming bacteria.
Step 2: Spores are resistant structures that allow bacteria to survive in harsh conditions.
Step 3: Feces contain these spore-forming bacteria due to contamination.
Step 4: When feces are deposited on soil, the spores of these bacteria enter the soil.
Step 5: Spores can remain dormant in soil for long periods.
Summary: Choice A is correct as spore-forming bacteria enter soil through feces, which act as a source of contamination. Choices B, C, and D are incorrect as they do not involve the direct introduction of spores into soil like feces do.
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Which of the following bacteria is known for producing a capsule that helps it avoid the immune system?
- A. Streptococcus pneumoniae
- B. Escherichia coli
- C. Salmonella enterica
- D. Bacillus subtilis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is known for producing a capsule that helps it evade the immune system. The capsule acts as a protective barrier, making it difficult for the immune system to recognize and attack the bacteria. Streptococcus pneumoniae is a common cause of pneumonia and meningitis.
Explanation for why other choices are incorrect:
B: Escherichia coli does not typically produce a capsule for immune evasion. It is more commonly associated with gastrointestinal infections.
C: Salmonella enterica also does not produce a capsule for immune evasion. It is known for causing foodborne illness.
D: Bacillus subtilis is a soil bacterium that is not known for producing a capsule to avoid the immune system.
A group of Ukrainian tourists returning from Samarqand was bringing with them gerbils. During examination in customs office ulcers were detected on the skin of the animals. What protozoa is the most likely to cause the disease in the animals, if mosquitoes are the carriers?
- A. Leishmania tropica major
- B. Balantidium coli
- C. P. falciparum
- D. T. cruzi
Correct Answer: C
Rationale: Rationale:
1. The presence of ulcers in animals suggests a parasitic infection.
2. Mosquitoes as carriers indicate a protozoan transmitted through insect bites.
3. Among the choices, Plasmodium falciparum causes malaria transmitted by mosquitoes.
4. Leishmania tropica major causes cutaneous leishmaniasis, not ulcers.
5. Balantidium coli causes intestinal infections, not skin ulcers.
6. Trypanosoma cruzi causes Chagas disease, not skin ulcers.
A man uses dentures. The dentist has noticed mucosal lecions with a white coating in his oral cavity. Microscopy of the coating detected large oval Gram-positive cells. What microorganisms have caused stomatitis in the patient?
- A. Yeast-like fungi of Candida genus
- B. Actinomycetes
- C. Streptococci
- D. Oral spirochetes
Correct Answer: A
Rationale: The correct answer is A: Yeast-like fungi of Candida genus. Candida is a common cause of oral thrush/stomatitis, characterized by mucosal lesions with white coating. The presence of large oval Gram-positive cells is indicative of Candida species. Actinomycetes (B) are filamentous bacteria and not oval Gram-positive cells. Streptococci (C) are spherical bacteria, not oval, and are not commonly associated with stomatitis. Oral spirochetes (D) are spiral-shaped bacteria and not oval Gram-positive cells typically seen in Candida infections. Thus, A is the correct choice based on the characteristic morphology and clinical presentation.
What is the function of bacterial ribosomes?
- A. DNA replication
- B. Protein synthesis
- C. Energy production
- D. Cell division
Correct Answer: B
Rationale: The correct answer is B: Protein synthesis. Bacterial ribosomes are responsible for translating the genetic information from mRNA into proteins. This process involves the binding of transfer RNA molecules carrying amino acids to the ribosome and the formation of peptide bonds between the amino acids to create proteins. DNA replication (A) is carried out by DNA polymerase enzymes, not ribosomes. Energy production (C) is primarily the function of mitochondria in eukaryotic cells, and cell division (D) is regulated by a complex network of proteins and signaling pathways, not ribosomes.
A patient with severe abdominal pain and diarrhea had a stool sample cultured. The bacteria were Gram-negative rods that did not ferment lactose. What is the most likely causative agent?
- A. Salmonella enterica
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: A
Rationale: The correct answer is A: Salmonella enterica. This is because Salmonella are Gram-negative rods that do not ferment lactose, which fits the description in the question. Additionally, Salmonella is a common cause of severe abdominal pain and diarrhea. Shigella dysenteriae is a Gram-negative rod that also causes severe diarrhea but it does not share the characteristic of not fermenting lactose. Escherichia coli is a Gram-negative rod that does ferment lactose. Proteus vulgaris is also a Gram-negative rod but it is not commonly associated with severe abdominal pain and diarrhea, making it an unlikely causative agent in this scenario.