Nokea
The process in which bacteria take up foreign DNA from the environment is called:
- A. Transformation
- B. Transduction
- C. Conjugation
- D. Binary fission
Correct Answer: A
Rationale: The correct answer is A: Transformation. During transformation, bacteria take up foreign DNA from the environment and incorporate it into their own genetic material. This process allows for genetic diversity and adaptation. Transduction (B) involves transfer of DNA via a virus, conjugation (C) involves direct transfer of DNA between bacterial cells, and binary fission (D) is a form of asexual reproduction in bacteria. Transformation is the only process specifically related to bacteria taking up foreign DNA.
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A stool sample from a patient with chronic diarrhea revealed 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 is because it is a protozoan parasite known to cause amoebic dysentery, presenting with chronic diarrhea and cysts with four nuclei in the stool sample. Giardia lamblia (B) causes giardiasis with trophozoites and cysts with two nuclei. Balantidium coli (C) is a ciliated parasite causing dysentery with large trophozoites. Trichomonas hominis (D) is a non-pathogenic flagellate often found in the human intestine. Thus, based on the specific characteristics of the cysts and clinical presentation, Entamoeba histolytica is the most likely causative agent.
Sanitary control is applied to monitor the quality of:
- A. Food, drinking water, restaurants, health care services and transport
- B. Food, drinking water
- C. Food, drinking water, restaurants and health care services
- D. Food, drinking water, and restaurants
Correct Answer: A
Rationale: The correct answer is A because sanitary control is crucial for monitoring the quality of a wide range of essential services to ensure public health and safety. Food safety, drinking water quality, cleanliness in restaurants, hygiene in healthcare settings, and transportation systems all fall under the purview of sanitary control. Therefore, option A is the most comprehensive and accurate choice.
Option B is incorrect because it does not include monitoring restaurants, health care services, and transport, which are important aspects of sanitary control. Option C is incorrect as it excludes transportation, an essential area that requires sanitary monitoring. Option D is incorrect as it does not cover health care services, which are critical for ensuring public health and safety.
A patient being treated for tuberculosis is suffering from hearing deterioration. What drug causes this complication?
- A. Streptomycin
- B. Isonicotinic acid hydrazide (Isoniazid)
- C. Rifampicin
- D. Ethionamide
Correct Answer: A
Rationale: The correct answer is A: Streptomycin. Streptomycin is an aminoglycoside antibiotic used to treat tuberculosis that can cause hearing loss as a side effect. It is known to damage the cochlear and vestibular organs in the inner ear. The other choices, B: Isoniazid, C: Rifampicin, and D: Ethionamide, are not associated with causing hearing deterioration as a side effect. Isoniazid can rarely cause peripheral neuropathy, Rifampicin can lead to hepatotoxicity, and Ethionamide may cause gastrointestinal disturbances, but none of these drugs are known to specifically cause hearing loss.
A patient with fever, enlarged lymph nodes, and bacteremia was diagnosed with plague. The Gram-stained smear revealed bipolar-staining, Gram-negative rods. What is the causative agent?
- A. Yersinia pestis
- B. Francisella tularensis
- C. Brucella abortus
- D. Clostridium botulinum
Correct Answer: A
Rationale: The correct answer is A: Yersinia pestis. Y. pestis is the causative agent of plague, characterized by fever, enlarged lymph nodes, and bacteremia. The bipolar-staining, Gram-negative rods seen on Gram stain are typical of Y. pestis.
Incorrect choices:
B: Francisella tularensis causes tularemia, not plague.
C: Brucella abortus causes brucellosis, not plague.
D: Clostridium botulinum causes botulism, not plague.
In summary, the key features of the patient's presentation and the Gram stain findings align with Yersinia pestis as the correct causative agent of plague.
Which bacteria are capable of producing exotoxins?
- A. Clostridium tetani
- B. Staphylococcus aureus
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Clostridium tetani, Staphylococcus aureus, and Escherichia coli are all capable of producing exotoxins. Exotoxins are proteins released by bacteria that can cause damage to the host. Clostridium tetani produces tetanospasmin, causing tetanus. Staphylococcus aureus produces toxins like enterotoxin and toxic shock syndrome toxin-1. Escherichia coli can produce Shiga toxin and heat-labile toxin. Therefore, all three bacteria listed can produce exotoxins, making choice D the correct answer. Choices A, B, and C are incorrect as they do not encompass all the bacteria capable of producing exotoxins.