Agglutination reaction is one of the following

Correct Answer: A

Rationale: The correct answer is A: Ascoli ring test. Agglutination reaction in the Ascoli ring test is characterized by the formation of a visible ring at the interface of antigen and antibody. This reaction specifically tests for the presence of specific antibodies against antigens in serum, indicating a recent or current infection. The other options, Western blot, ELISA, and Reaction type Gruber, do not involve the agglutination reaction. Western blot and ELISA are immunoassay techniques that detect specific antibodies or antigens, while Reaction type Gruber is not a recognized method in immunology. Therefore, the Ascoli ring test is the correct choice for a test involving agglutination reaction.

Correct Answer: A

Rationale: The correct answer is A: Cytopathic effect. This is because polioviruses cause visible changes in infected cells, leading to cell damage and death, known as cytopathic effect. This is a key characteristic of viral infection. Choice B (Cytotoxic effect) is incorrect as it refers to the toxicity of a substance to cells, not the specific effect of polioviruses. Choice C (Cytolytic effect) is incorrect as it specifically refers to cell lysis, which is not the primary mechanism of poliovirus infection. Choice D (They Don't Change The Cell Cultures) is incorrect because polioviruses do indeed cause changes in cell cultures due to their cytopathic effect.

Correct Answer: A

Rationale: Step-by-step rationale for why choice A is correct: 1. Helicobacter pylori, the bacteria causing helicobacteriosis, is microaerophilic, requiring low oxygen levels. 2. Cultivation conditions must mimic the natural environment of the bacteria. 3. Failure to provide a microaerophilic environment can hinder bacterial growth. 4. Thus, the ability to cultivate these bacteria requires consideration of their microaerophilic nature. Summary: - Choice A is correct because Helicobacter pylori is a microaerophilic bacteria. - Choice B (Presence of urease) is incorrect as it is a characteristic used for diagnosis, not cultivation. - Choice C (Absence of spores and capsules) is incorrect as it does not relate to cultivation requirements. - Choice D (Colonization of gastral cells) is incorrect as it pertains to bacterial behavior, not cultivation needs.

Correct Answer: B

Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.

Correct Answer: D

Rationale: The thin microorganisms described with 12-14 equal ringlets and pale-pink sharp points are characteristic of Borrelia spirochetes, the causative agent of relapsing fever. The ringlet appearance corresponds to the characteristic coiled structure of Borrelia spirochetes. The length of 10-13 mkm falls within the typical size range of Borrelia spirochetes. This pathogen is commonly identified in Romanovsky-Giemsa stained samples from patients with relapsing fever. Summary of other choices: A: Leishmaniasis - Leishmania parasites are larger and do not have the described ringlets or pale-pink sharp points. B: Leptospirosis - Leptospira bacteria are not described as having ringlets or pale-pink sharp points. C: Surra - Surra is caused by Trypanosoma evansi, and the description does not match the characteristics of this parasite.

Correct Answer: A

Rationale: The correct answer is A: Type 1 hypersensitivity reaction. In this type of reaction, allergens trigger the production of IgE antibodies, leading to mast cell and basophil degranulation and release of inflammatory mediators like histamine. This causes immediate allergic symptoms. Seafood and eggs are common allergens that can elicit this response. B: Type 2 hypersensitivity reaction involves antibodies targeting cell surface or extracellular matrix antigens, leading to cell destruction or dysfunction. This is not the mechanism in seafood or egg allergies. C: Type 3 hypersensitivity reaction involves immune complex deposition in tissues, leading to inflammation and tissue damage. This is not the mechanism in seafood or egg allergies. D: Type 4 hypersensitivity reaction is cell-mediated and involves T cells causing inflammation and tissue damage. This is not the mechanism in seafood or egg allergies.

Correct Answer: C

Rationale: Rationale: 1. Vaccinia is a laboratory product used in smallpox vaccination. 2. Variola is the virus that causes smallpox, not a laboratory product. 3. Monkeypox is a naturally occurring virus, not a laboratory product. 4. Cowpox can be found in nature and is used in vaccine production, but it is not a laboratory product like Vaccinia.

Correct Answer: A

Rationale: The correct answer is A: Clostridia. Fusiform spore-forming microorganisms that stain violet-blue with Gram's stain are characteristic of Clostridia. Clostridia are anaerobic, rod-shaped bacteria known for their ability to form spores and cause diseases such as tetanus and botulism. Summary of other choices: B: Streptococci are spherical, not fusiform, and typically do not form spores. C: Spirochaete are spiral-shaped bacteria and do not typically form spores. D: Actinomycete are filamentous bacteria that do not typically form spores and do not stain violet-blue with Gram's stain.

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. Enteropathogenic E. coli (EPEC) attach to enterocytes via a type III secretion system. 2. Once attached, they form attaching and effacing lesions on the microvilli, leading to microvillus destruction. 3. This mechanism allows EPEC to cause diarrhea by disrupting the normal absorptive function of the intestines. Summary: - B (They are invasive and produce enterotoxin) is incorrect because EPEC are non-invasive and do not produce enterotoxins. - C (Cause disease clinically similar to bacterial) is vague and does not provide specific information about EPEC pathogenesis. - D (None of the above) is incorrect as A is the correct explanation for EPEC pathogenicity.