Which of the following can be used for specific prophylaxis of pertussis?

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Question 1 of 9

Which of the following can be used for specific prophylaxis of pertussis?

Correct Answer: A

Rationale: The correct answer is A: Pertussis toxoid. This is because pertussis toxoid is a component of the pertussis vaccine, which provides specific prophylaxis against pertussis by stimulating the immune system to produce antibodies against the bacteria causing the disease. Choice B, killed vaccine, is incorrect as it does not specify pertussis toxoid. Choice C, wide-spectrum antibiotics, is incorrect as antibiotics are used for treatment, not prophylaxis. Choice D, None of the above, is incorrect as pertussis toxoid is specifically used for prophylaxis of pertussis.

Question 2 of 9

A smear of sputum from the patient with suspected lobar pneumonia was stained with the use of the following stains and reagents: solution of gentian violet, Lugol's solution, 96o alcohol, water-magenta. What staining method was applied in this case?

Correct Answer: A

Rationale: The correct answer is A: Gram staining method. This method involves staining with gentian violet, followed by Lugol's solution, 96% alcohol decolorization, and counterstaining with safranin or water-magenta. This staining sequence allows for the differentiation of bacteria based on their cell wall composition. In the case of lobar pneumonia, the causative agent is typically a bacterium with a cell wall that retains the crystal violet stain after decolorization with alcohol, indicating a Gram-positive bacterium. Summary of Incorrect Choices: B: Ziehl-Nielsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for lobar pneumonia. C: Romanovsky staining is primarily used in the identification of blood cells and blood parasites, not for bacteria. D: Neisser staining is not a commonly used staining method in microbiology for bacterial identification.

Question 3 of 9

A patient being treated in the burns department has suppurative complication. The pus is of bluish- green color that is indicative of infection caused by Pseudomonas aeruginosa. What factor is typical for this causative agent?

Correct Answer: A

Rationale: The correct answer is A: Gram-negative stain. Pseudomonas aeruginosa is a gram-negative bacterium, as indicated by the bluish-green pus color. This bacterium has an outer membrane that retains the crystal violet stain, making it appear pink/red after the counterstain with safranin in Gram staining. The other choices are incorrect because Pseudomonas aeruginosa does not typically form spores (B), has a rod-shaped morphology rather than a coccal form (C), and does not exhibit cell pairing (D).

Question 4 of 9

A patient had been provisionally diagnosed with syphilis. A laboratory assistant took the blood serum for an immunologic test based on the detection of antibodies preventing the movement of treponemas and causing their death. What reaction was used for the diagnosis?

Correct Answer: A

Rationale: The correct answer is A: Immobilization. This technique is called the Treponema pallidum immobilization (TPI) test, used to diagnose syphilis. The rationale is as follows: 1. TPI test detects antibodies that prevent the movement of treponemas, causing their death. 2. By immobilizing the treponemas, it indicates the presence of specific antibodies against syphilis. 3. This test is highly specific for syphilis diagnosis as it directly targets the causative agent. Other choices are incorrect: B: Complement binding - Not specific to syphilis, more commonly used for other diseases. C: Agglutination - Detects clumping of particles, not specific to treponemas or syphilis. D: Precipitation - Involves the formation of a solid, not directly related to treponema movement or death.

Question 5 of 9

Which of the following media is the most selective for Vibrio cholerae?

Correct Answer: D

Rationale: The correct answer is D: TCBS. Thiosulfate-citrate-bile salts-sucrose (TCBS) agar is the most selective for Vibrio cholerae due to its high salt content, bile salts, and sucrose. Vibrio cholerae can grow well in alkaline conditions, which are provided by TCBS agar. MacConkey's agar (A) is selective for gram-negative bacteria, but not specifically for Vibrio cholerae. Chocolate agar (B) is a non-selective medium suitable for fastidious organisms. SS agar (C) is selective for Salmonella and Shigella species, not Vibrio cholerae.

Question 6 of 9

Which of the following infections is typical for the lower respiratory tract?

Correct Answer: D

Rationale: The correct answer is D: Q-fever. Q-fever is typically an infection that affects the lower respiratory tract, causing symptoms like pneumonia. Haemophilus influenzae pharyngitis (choice A) is an upper respiratory tract infection. Ozeana (choice B) and diphtherial croup (choice C) are not specific infections related to the lower respiratory tract. Q-fever stands out as the correct choice due to its association with lower respiratory tract infections.

Question 7 of 9

A wound culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely microorganism?

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters indicates a staphylococcal species. The fact that the bacteria are catalase-positive and coagulase-negative further narrow it down to Staphylococcus epidermidis, as this species fits all the given characteristics. - Choice B, Staphylococcus aureus, is coagulase-positive. - Choice C, Streptococcus pyogenes, is a streptococcal species, not staphylococcal. - Choice D, Enterococcus faecalis, is a Gram-positive cocci but is catalase-negative and not typically found in clusters.

Question 8 of 9

While examining a blood smear taken form a patient and stained by Romanovsky's method a doctor revealed some protozoa and diagnozed the patient with Chagas disease. What protozoan is the causative agent of this disease?

Correct Answer: A

Rationale: Rationale: 1. Chagas disease is caused by Trypanosoma cruzi. 2. Trypanosoma cruzi is transmitted by triatomine bugs. 3. On a blood smear stained with Romanovsky's method, Trypanosoma cruzi appears as trypomastigotes. 4. Toxoplasma gondii causes toxoplasmosis, not Chagas disease. 5. Leishmania donovani and Leishmania tropica cause different forms of leishmaniasis, not Chagas disease.

Question 9 of 9

A healthy man is in a region with high risk of catching malaria. What drug should be administered for individual chemoprophylaxis of malaria?

Correct Answer: A

Rationale: The correct answer is A: Chingamin (also known as Chloroquine). Chingamin is the drug of choice for chemoprophylaxis of malaria in regions with high risk. It is effective against Plasmodium falciparum, the most common malaria parasite. Chingamin is well-tolerated, affordable, and has a long track record of use. Sulfalen (Choice B) is not commonly used for malaria prophylaxis. Tetracycline (Choice C) is not recommended for malaria prophylaxis due to poor efficacy and resistance development. Metronidazole (Choice D) is not effective against malaria parasites.

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