What type of immune reaction is most common in identification of vibrio cholerae

Correct Answer: A

Rationale: The correct answer is A: Agglutination. Agglutination is commonly used to identify Vibrio cholerae by clumping together the bacteria with specific antibodies. This reaction occurs when antibodies bind to antigens on the bacterial surface, leading to visible clumps. In contrast, Precipitation, Western blot, and ELISA are not typically used to identify Vibrio cholerae. Precipitation involves antigen-antibody complexes becoming insoluble, Western blot is used for protein detection, and ELISA is commonly used for detecting specific antigens or antibodies in a sample. Agglutination is the most appropriate choice for identifying Vibrio cholerae due to its specific interaction with the bacteria's surface antigens.

Correct Answer: C

Rationale: The correct answer is C: Rickettsia. Rickettsia is a host-dependent bacterium because it requires living cells of a host organism to survive and replicate. This bacterium is an obligate intracellular pathogen, meaning it cannot grow outside of a host cell. A: Mycoplasma and B: Ureaplasma are not host-dependent as they can grow and reproduce in cell-free environments due to possessing their own unique cell wall structures. D: Micrococcus is a free-living bacterium that can survive and reproduce independently without relying on a host organism.

Correct Answer: A

Rationale: The correct answer is A: Tuberculin. The Mantoux test involves injecting tuberculin, a protein derivative of Mycobacterium tuberculosis, under the skin to check for a delayed hypersensitivity reaction in individuals exposed to TB. B: BCG vaccine is a live attenuated vaccine used for TB prevention, not for diagnostic testing. C: DTP vaccine is for diphtheria, tetanus, and pertussis, not TB. D: Tularinum is not a standard immunobiological preparation used for TB testing. Therefore, A is the correct choice for the Mantoux test.

Correct Answer: B

Rationale: Rationale: 1. Enteropathogenic E.coli (EPEC) adheres to the intestinal wall using bundle-forming pili. 2. EPEC produces toxins that disrupt cell structure and function, leading to diarrhea. 3. Shigella spp. invade intestinal cells, Salmonella spp. invade and multiply within cells, and Vibrio cholerae produces cholera toxin causing profuse watery diarrhea. Summary: A, C, and D choices are incorrect because they do not specifically adhere to the intestine wall and produce toxins like EPEC does.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This is because it is the only choice that matches the description of cysts with four nuclei, characteristic of Entamoeba histolytica. Entamoeba histolytica is a protozoan parasite that causes amoebiasis, leading to symptoms like persistent diarrhea. The other choices can be eliminated for the following reasons: B: Balantidium coli - It is a ciliated protozoan that causes dysentery in humans but does not produce cysts with four nuclei. C: Giardia lamblia - It is a flagellated protozoan that causes giardiasis, but it forms cysts with only two nuclei. D: Trichomonas hominis - It is a flagellated protozoan found in the human intestine, but it does not produce cysts with four nuclei. Therefore, based on the description of cysts with four nuclei in the stool sample,

Correct Answer: D

Rationale: Rationale: 1. Rickettsiae are obligate intracellular bacteria, hence they do not form spores, capsules, or flagella. 2. They have a slim glycocalyx layer, aiding in attachment to host cells. 3. Bipolar fimbriae are structures that help in adhesion to host cells. Therefore, all statements (A, B, and C) are true for Rickettsiae, making option D the correct answer. Other choices are incorrect as they do not accurately describe the characteristics of Rickettsiae.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is a common cause of pneumonia and is characterized by Gram-positive diplococci with a capsule. The presence of a capsule helps the bacterium evade the immune system and contributes to its virulence. Klebsiella pneumoniae (B) is a Gram-negative bacterium and does not typically have a capsule. Neisseria meningitidis (C) is a Gram-negative diplococcus and is associated with meningitis, not pneumonia. Staphylococcus aureus (D) is a Gram-positive bacterium, but it does not typically present as diplococci with a capsule in a sputum smear from a pneumonia patient.

Correct Answer: A

Rationale: The correct answer is A: HIV. HIV is an example of obligate parasitism because it requires a host cell to replicate and survive. It cannot live independently outside of a host organism. In contrast, choices B, C, and D are not obligate parasites. E. Coli and S. Epidermidis are examples of commensal bacteria that can live in the host without causing harm. Pseudomonas aeruginosa can be both an opportunistic pathogen and a free-living organism, not strictly dependent on a host for survival.

Correct Answer: C

Rationale: The correct answer is C, transplacental mechanism. Listeria monocytogenes can cross the placenta, infecting the fetus during pregnancy. This mechanism allows the bacteria to be transmitted from mother to baby in utero. Alimentary mechanism (A) involves ingestion of contaminated food, not direct transfer between individuals. Transmission (B) is a broad term that doesn't specify the specific route of Listeria transmission. Physical contact (D) is not a common mode of Listeria transmission compared to transplacental transmission in the case of maternal-fetal infection.