A patient with a long history of chronic gastritis undergoes a gastroscopy, which detects an ulcer in the duodenum area. Microscopic examination of the tissue biopsy developed Gram-negative curved bacteria and the rapid urease activity test of the biopsy material was highly positive. The most likely cause of the disease is:

Correct Answer: D

Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.

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.

Correct Answer: D

Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.

Correct Answer: A

Rationale: The correct answer is A: Helicobacterial infection. This is the most probable leading mechanism of disease development in this case because the patient's symptoms, such as heartburn, epigastric pain, food intolerance, and presence of a duodenal ulcer with a positive urease test, are classic signs of Helicobacter pylori infection. This bacterium colonizes the stomach lining, leading to inflammation and ulcer formation. The exacerbations in spring and autumn could be due to seasonal variations in immune response. Choice B: Dietary allergy is incorrect because the symptoms and findings in the patient are more indicative of an infectious etiology rather than an allergic reaction to specific foods. Choice C: Autoantibody production is unlikely as there are no indications of an autoimmune process in this case. Choice D: Reduced prostaglandin synthesis is not the leading mechanism as the symptoms and findings are more consistent with an infectious cause rather than a deficiency in prostaglandin synthesis.

Correct Answer: B

Rationale: The function of bacterial pili is to aid in adhesion. Pili are hair-like structures on the bacterial surface that help the bacteria attach to surfaces or other cells. This adhesion is crucial for colonization and infection. Pili do not provide motility, as that is typically done by flagella. Bacteria form spores for survival under harsh conditions, and protein synthesis is carried out by ribosomes, not pili. Thus, the correct answer is B, aiding in adhesion.

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.

Correct Answer: A

Rationale: Osmosis is the correct answer because it is the process by which water molecules move across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. This movement occurs passively, driven by the concentration gradient. Facilitated diffusion (B) involves the transport of specific molecules with the help of carrier proteins, not water. Phagocytosis (C) is a process where cells engulf solid particles, not water molecules. Exocytosis (D) is the process of releasing substances from a cell by fusion of vesicles with the cell membrane, not the transport of water across the membrane.

Correct Answer: B

Rationale: The correct answer is B: Outer membrane containing lipopolysaccharides. Gram-negative bacteria have an outer membrane that contains lipopolysaccharides, which are important for protection and pathogenicity. This outer membrane is a unique feature of Gram-negative bacteria and is not present in Gram-positive bacteria, making it a key characteristic. A: Incorrect because Gram-negative bacteria have a thin peptidoglycan layer compared to Gram-positive bacteria. C: Incorrect because teichoic acids are a characteristic of Gram-positive bacteria, not Gram-negative bacteria. D: Incorrect because all bacteria, including Gram-negative bacteria, have a cell wall.

Correct Answer: C

Rationale: The correct answer is C, as Gram-negative bacteria have a cell wall containing lipopolysaccharides. This outer membrane structure is unique to Gram-negative bacteria and plays a critical role in pathogenicity and immune response. Teichoic acid (choice A) is found in Gram-positive bacteria. The cell wall of Gram-negative bacteria is thinner than that of Gram-positive bacteria (choice B). The cell wall of Gram-negative bacteria is not composed entirely of peptidoglycan (choice D), as it also contains other components like lipopolysaccharides.