Nokea
What type of bacteria is responsible for the formation of acid in the stomach?
- A. Staphylococcus aureus
- B. Helicobacter pylori
- C. Bacillus cereus
- D. Clostridium botulinum
Correct Answer: B
Rationale: The correct answer is B: Helicobacter pylori. This bacterium is responsible for stomach acid formation by producing an enzyme called urease, which converts urea into ammonia and carbon dioxide, leading to an increase in stomach pH. Staphylococcus aureus (A) does not cause stomach acid formation. Bacillus cereus (C) and Clostridium botulinum (D) are not involved in stomach acid processes.
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The organisms to be identified have a nucleus surrounded by a nuclear membrane. Genetic material is concentrated predominantly in the chromosomes which consist of DNA strands and protein molecules. These cells divide mitotically. Identify these organisms:
- A. Eukaryotes
- B. Bacteriophages
- C. Prokaryotes
- D. Viruses
Correct Answer: A
Rationale: Step-by-step rationale:
1. The presence of a nucleus with a nuclear membrane indicates eukaryotic cells.
2. Eukaryotes have genetic material in chromosomes made of DNA and proteins.
3. Mitotic division is characteristic of eukaryotic cells.
4. Therefore, the organisms described are eukaryotes.
Summary:
- Bacteriophages (B) are viruses that infect bacteria.
- Prokaryotes (C) lack a nucleus and their genetic material is not organized into chromosomes.
- Viruses (D) are not considered living organisms and do not have a nucleus or chromosomes.
During sanitary and bacteriological testing of water with the membrane filter technique there were revealed two red colonies on a membrane filter (Endo agar) through which 500 ml of water was filtred. Calculate the coli index and coli titer of the analyzed water:
- A. 4 and 250
- B. 2 and 500
- C. 250 and 4
- D. 500 and 2
Correct Answer: C
Rationale: The correct answer is C (coli index of 250 and coli titer of 4). The coli index is calculated by multiplying the number of colonies by the reciprocal of the volume filtered, which gives 2 colonies x (1/0.5 L) = 4. The coli titer is obtained by dividing the volume filtered by the number of colonies, which gives 0.5 L / 2 colonies = 0.25 L or 250 ml. This indicates the concentration of coliform bacteria in the water sample.
Choice A (4 and 250) is incorrect because it has the correct coli index but the values are reversed for coli index and coli titer. Choice B (2 and 500) is incorrect as it provides the correct coli titer value but the values are reversed for coli index and coli titer. Choice D (500 and 2) is incorrect because it reverses the values for both coli index and coli titer.
All statements about plasmids are correct except:
- A. Many plasmids contain genes that confer resistance to one or more antibiotics
- B. Are smaller, circular, extrachromosomal DNAs
- C. Plasmids encode essential bacteria properties
- D. Plasmids are responsible for the bacterial conjugation
Correct Answer: C
Rationale: The correct answer is C because plasmids do not encode essential bacterial properties. They are non-essential, extra-chromosomal DNA molecules that can replicate independently within bacterial cells. Plasmids mainly contain genes for antibiotic resistance, genetic transfer, and other specific functions. Choice A is correct as many plasmids do carry antibiotic resistance genes. Choice B is also accurate as plasmids are indeed smaller, circular, and exist outside the bacterial chromosome. Choice D is true as plasmids can facilitate bacterial conjugation, allowing the transfer of genetic material between bacteria.
The bacteria that produces a thick pseudomembrane in the throat is:
- A. Corynebacterium diphtheriae
- B. Streptococcus pyogenes
- C. Neisseria meningitidis
- D. Bacillus cereus
Correct Answer: A
Rationale: Rationale:
1. Corynebacterium diphtheriae is the correct answer as it is the bacteria responsible for causing diphtheria, characterized by a thick pseudomembrane in the throat.
2. Streptococcus pyogenes causes strep throat but does not produce a pseudomembrane.
3. Neisseria meningitidis causes meningitis and septicemia, not a throat pseudomembrane.
4. Bacillus cereus causes food poisoning, not throat-related symptoms.
Patients with similar complaints applied to the doctor: weakness, pain in the intestines, disorder of GIT. Examination of the feces revealed that one patient with four nucleus cysts should be hospitalized immediately. For what protozoa are such cysts typical?
- A. Lamblia
- B. Dysenteric amoeba
- C. Balantidium
- D. Trichomonas
Correct Answer: B
Rationale: The correct answer is B: Dysenteric amoeba.
1. Dysenteric amoeba causes amoebiasis, which presents with symptoms like weakness, intestinal pain, and gastrointestinal disorders.
2. The presence of four-nucleus cysts in the feces indicates an infection with Entamoeba histolytica, the causative agent of amoebiasis.
3. Multiple-nucleus cysts are characteristic of Entamoeba histolytica, distinguishing it from other protozoa.
4. Lamblia (choice A), Balantidium (choice C), and Trichomonas (choice D) are not associated with four-nucleus cysts or the mentioned symptoms, making them incorrect choices.