During fibergastroscopy a patient with ulcer disease of the stomach, the mucosal biopsy is taken from the area of an ulcer. Impression smear is prepared from biopsy material and stained by Gram method; the rest of biopsy material is tested for urease activity. Microscopy of the impression smear revealed gram- negative spiral-shaped microorganisms, urease activity test is positive. What bacteria were detected?

Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. Rationale: 1. Gram-negative spiral-shaped microorganisms match the morphology of Helicobacter pylori. 2. Positive urease activity is a characteristic feature of Helicjsonacter pylori. 3. Helicobacter pylori is specifically associated with gastric ulcers and is a common pathogen in the gastrointestinal tract. Summary: Choice B, Campilobacter jejuni, is a gram-negative curved bacterium but is not typically associated with gastric ulcers or urease activity. Choice C, Treponema pallidum, is a spirochete bacterium causing syphilis, which is not related to gastric ulcers. Choice D, Spirilla minor, is a generic term for spiral-shaped bacteria and is not a specific pathogen associated with gastric ulcers or urease activity.

Correct Answer: C

Rationale: The correct answer is C: Erysipelas. Erysipelas is a type of acute infection caused by group A Streptococcus bacteria. This bacteria infects the upper dermis and superficial lymphatics, leading to a distinct raised, well-demarcated, erythematous skin lesion. The other choices are incorrect because: A Carbuncle is a deep skin infection involving hair follicles, B Impetigo is a superficial skin infection caused by Staphylococcus or Streptococcus bacteria, and D Acne is a chronic inflammatory skin condition not typically caused by group A Streptococcus.

Correct Answer: B

Rationale: The correct answer is B: caliciviruses. Caliciviruses are known to be (+) ssRNA viruses that cause gastroenteritis in a wide range of animals, including birds, cats, dogs, pigs, sheep, cows, and humans. These viruses are highly contagious and can spread through contaminated food or water. Rotaviruses (A) are also a common cause of gastroenteritis, but they are not exclusively isolated from the mentioned animals. Adenoviruses (C) typically cause respiratory or eye infections, not gastroenteritis. Noroviruses (D) are also a major cause of gastroenteritis in humans, but they are not commonly found in animals other than humans.

Correct Answer: D

Rationale: The correct answer is D: Loefler. This staining method is used for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. It involves using methylene blue and basic fuchsin to stain the bacteria. The yellow bacilli with blue grains at their ends indicate the characteristic appearance of C. diphtheriae when stained using the Loefler method. Choice A: Ziehl-Nielsen is used for acid-fast bacteria like Mycobacterium tuberculosis. Choice B: Kozlovsky is not a standard staining method in microbiology. Choice C: Romanovsky is used for blood smears to identify malaria parasites.

Correct Answer: B

Rationale: The correct answer is B: Clostridium tetani. This bacterium produces tetanospasmin toxin, causing tetanus. Clostridium botulinum (choice A) produces botulinum toxin, leading to botulism. Bacillus anthracis (choice C) causes anthrax, not tetanus. Staphylococcus aureus (choice D) can cause various infections, but not tetanus. Therefore, only Clostridium tetani is the causative agent of tetanus.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a flagellated protozoan with two nuclei, known as the "falling leaf" appearance. It causes diarrhea in humans through ingestion of contaminated water or food. Entamoeba histolytica causes amoebic dysentery, characterized by bloody diarrhea and colitis. Trichomonas vaginalis is a sexually transmitted protozoan causing vaginal discharge but is not found in stool. Balantidium coli is a ciliated protozoan causing diarrhea but does not have flagellated forms.

Correct Answer: A

Rationale: Rationale: 1. Thin, pale pink microorganisms with spiral coils suggest Treponema pallidum, the causative agent of syphilis. 2. Staining with Romanovsky-Giemsa method highlights the characteristic morphology of T. pallidum. 3. Syphilis presents with various stages and symptoms, correlating with the lymph node involvement. 4. Leptospirosis is caused by Leptospira interrogans, presenting with different clinical features. 5. Relapsing fever is caused by Borrelia species, which do not match the description. 6. Trypanosomiasis is caused by Trypanosoma species, which have distinct morphology and staining properties.

Correct Answer: A

Rationale: The correct answer is A: vectors. Vectors are animals that transmit infectious diseases from one host to another, typically through biting or contact. They do not cause the disease themselves but serve as intermediaries. Pathogens (B) are the microorganisms that cause diseases. Carriers (C) are individuals who harbor a pathogen without showing symptoms. Parasites (D) are organisms that live on or inside another organism and may or may not transmit diseases. Therefore, the term "vectors" specifically refers to animals that transmit infectious diseases, making it the correct choice in this context.

Correct Answer: A

Rationale: The correct answer is A: Helicobacter pylori. Rationale: 1. Gram-negative spiral-shaped microorganisms match the morphology of Helicobacter pylori. 2. Positive urease activity is a characteristic feature of Helicjsonacter pylori. 3. Helicobacter pylori is specifically associated with gastric ulcers and is a common pathogen in the gastrointestinal tract. Summary: Choice B, Campilobacter jejuni, is a gram-negative curved bacterium but is not typically associated with gastric ulcers or urease activity. Choice C, Treponema pallidum, is a spirochete bacterium causing syphilis, which is not related to gastric ulcers. Choice D, Spirilla minor, is a generic term for spiral-shaped bacteria and is not a specific pathogen associated with gastric ulcers or urease activity.