Non - complete phagocytosis is observed during infections with:

Correct Answer: D

Rationale: Rationale: 1. Mycobacterium tuberculosis, Legionella pneumophila, Brucella melitensis can evade complete phagocytosis. 2. Mycobacterium tuberculosis inhibits phagosome-lysosome fusion. 3. Legionella pneumophila can prevent phagosome maturation. 4. Brucella melitensis can survive and replicate within phagocytes. 5. A + B + C together represent non-complete phagocytosis. Summary: - A, B, C individually cause incomplete phagocytosis. - Only when all three are present together (D) is non-complete phagocytosis observed.

Correct Answer: D

Rationale: Certainly! The correct answer is D: Pertussis exotoxin. Pertussis toxin primarily affects the respiratory system causing whooping cough. It does not directly target the nervous system like the other toxins listed. Tetanospasmin causes muscle spasms, Diphtheria exotoxin affects the heart and nerves, and Botulinum exotoxin causes paralysis by blocking neurotransmitter release. Therefore, Pertussis exotoxin is the only toxin among the options that does not manifest with neurological symptoms.

Correct Answer: C

Rationale: The correct answer is C: Reaction haemagglutination inhibition. This method is used to detect antibodies against influenza viruses by measuring the ability of the patient's serum to inhibit haemagglutination. This is a specific and sensitive technique for detecting influenza antibodies. A: Agglutination reaction is not specific for influenza viruses and may give false positives. B: Precipitation reaction in agar gel is not typically used for detecting influenza antibodies. D: Ration haemagglutination is not a standard method for detecting influenza antibodies.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. Staphylococcus aureus is a Gram-positive bacterium that commonly presents as cocci in clusters. It is a known causative agent of abscesses due to its ability to produce enzymes and toxins that contribute to tissue destruction. In this case, the presence of Gram-positive cocci in clusters aligns with the characteristic morphology of Staphylococcus aureus. Summary of incorrect choices: B: Streptococcus pyogenes is a Gram-positive bacterium that typically presents as cocci in chains, not clusters. It is more commonly associated with pharyngitis and skin infections rather than abscesses. C: Enterococcus faecalis is a Gram-positive bacterium that typically presents as cocci in pairs or short chains, not clusters. It is more commonly associated with urinary tract infections and endocarditis. D: Micrococcus luteus is a Gram-positive bacterium that typically presents as t

Correct Answer: B

Rationale: The correct answer is B because retroviruses, including those in the Family Retroviridae, have a capsid consisting of two copies of single-stranded RNA (ssRNA). This is a defining characteristic of retroviruses, which use reverse transcriptase to convert their ssRNA into DNA. This DNA is then integrated into the host cell's genome. Choices A, C, and D are incorrect because Family Retroviridae viruses are not helical non-enveloped viruses (C), they are not helical enveloped viruses (A), and they do not have a complex type of symmetry (D).

Correct Answer: A

Rationale: The correct answer is A: Blood agar. Streptococcus pneumoniae is a fastidious bacterium that requires enriched media for growth. Blood agar provides the necessary nutrients and growth factors for the cultivation of S. pneumoniae, such as blood proteins and hemin. MacConkey agar (B) is selective for gram-negative bacteria and would not support the growth of S. pneumoniae. Peptone water (C) is a liquid medium that lacks the necessary nutrients for the growth of S. pneumoniae. Choice D is incorrect as blood agar is a suitable medium for cultivating S. pneumoniae.

Correct Answer: A

Rationale: Peptidoglycan is a major component of bacterial cell walls, providing structural support and protection. The correct answer is A because peptidoglycan is typically found in the cell wall of bacteria. The cell wall is crucial for maintaining the shape of the bacterial cell and protecting it from external stresses. The plasma membrane (choice B) is primarily composed of phospholipids and proteins, not peptidoglycan. The nucleus (choice C) is found in eukaryotic cells and contains genetic material, not peptidoglycan. The endoplasmic reticulum (choice D) is an organelle involved in protein synthesis and lipid metabolism, but it does not contain peptidoglycan. Therefore, the correct answer is A as peptidoglycan is typically found in the cell wall of bacteria.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoan parasite causes amoebic dysentery and is characterized by cysts with four nuclei in fecal smears. It is commonly associated with chronic diarrhea. Balantidium coli (B) presents with large ciliated trophozoites, not cysts. Giardia lamblia (C) has trophozoites with flagella and causes giardiasis, not cysts with four nuclei. Trichomonas hominis (D) typically has a pear-shaped trophozoite and is not associated with cysts with four nuclei.

Correct Answer: A

Rationale: The correct answer is A: Amebiasis. Amebiasis is caused by the parasite Entamoeba histolytica, presenting with symptoms like acute abdominal pain, bloody diarrhea with mucus, and inconstant shape organisms seen in fecal smear. The presence of erythrocytes supports the diagnosis due to the parasite's ability to invade intestinal mucosa causing bleeding. Choice B (Lambliasis) presents with different symptoms like steatorrhea and fatigue. Choice C (Schistosomiasis) is mainly associated with liver and urinary symptoms. Choice D (Intestinal trichomoniasis) commonly presents with watery diarrhea and does not typically cause bloody stools. Therefore, based on the patient's symptoms and fecal smear findings, Amebiasis is the most likely diagnosis.