Nokea
Disinfection is:
- A. method for destruction of spore forms of microorganisms
- B. method for destruction of vegetative and spore forms of microorganisms
- C. method to destroy the vegetative forms of microorganism, but their spores may survive
- D. method for determination of the effect of physical agents on the microorganism
Correct Answer: C
Rationale: Disinfection is the process of destroying the vegetative forms of microorganisms, but their spores may survive. This is why choice C is correct. The other choices are incorrect because:
A: Disinfection does not necessarily target spore forms exclusively.
B: While disinfection targets vegetative forms, it does not always eliminate spore forms.
D: Disinfection is not primarily used for determining the effect of physical agents on microorganisms.
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In which of the following disease, the respiratory tract is infected:
- A. Tuberculosis
- B. Q-fever
- C. Legionnaires disease
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Tuberculosis, Q-fever, and Legionnaires disease all can infect the respiratory tract. Tuberculosis is a bacterial infection affecting the lungs, Q-fever is caused by a bacterium that primarily affects the lungs, and Legionnaires disease is a severe form of pneumonia. All three diseases specifically target the respiratory system, making them the correct choices. Choices A, B, and C are incorrect because each of them individually infects the respiratory tract, not just one or two of them.
A 23-year-old man developed a perforation in his hard palate, a dense formation with clear margins was detected in this area. After a surgery, microscopy of excised formation shows there a large focus of caseous necrosis surrounded with a granulation tissue with endovasculitis and a cellular infiltration consisting of lymphocytes and epithelioid cells with predominance of plasma cells. What is the most likely disease in this case?
- A. Syphilis
- B. Tuberculosis
- C. Leprosy
- D. Scleroma
Correct Answer: B
Rationale: The correct answer is B: Tuberculosis. The case describes a man with a perforation in the hard palate and features of caseous necrosis with granulation tissue, endovasculitis, and a cellular infiltration mainly of lymphocytes, epithelioid cells, and plasma cells. These findings are classic for tuberculosis infection, commonly seen in extrapulmonary sites like the oral cavity. Syphilis (choice A) typically presents with a painless ulcer and different histopathological features. Leprosy (choice C) presents with granulomas containing foamy macrophages. Scleroma (choice D) is caused by Klebsiella rhinoscleromatis and presents with chronic granulomatous inflammation.
Which bacteria is commonly associated with hospital-acquired infections?
- A. Escherichia coli
- B. Clostridium difficile
- C. Staphylococcus aureus
- D. Bacillus anthracis
Correct Answer: C
Rationale: The correct answer is C: Staphylococcus aureus. This bacterium is commonly associated with hospital-acquired infections due to its ability to cause a wide range of infections and its resistance to multiple antibiotics. Staphylococcus aureus can cause skin infections, pneumonia, bloodstream infections, and surgical site infections, making it a significant threat in healthcare settings. Escherichia coli (choice A) is more commonly associated with foodborne illnesses. Clostridium difficile (choice B) is known for causing antibiotic-associated diarrhea. Bacillus anthracis (choice D) is primarily associated with anthrax infections, which are not typically acquired in hospital settings.
A 43-year-old cattle farm worker is brought to the surgeon with fever, malaise, and inflamed lesions on his hands and arms. He reports that about 2 weeks before his presentation at the hospital he noticed small, painless, pruritic papules that quickly enlarged and developed a central vesicle. The vesicles developed into erosion and left painless necrotic ulcers with black, depressed eschar. Gram's staining of the ulcer reveals gram-positive spore-forming bacilli. Which of the following diseases is the most likely cause of these findings?
- A. Anthrax
- B. Chickenpox
- C. Syphilis
- D. Tularemia
Correct Answer: A
Rationale: The correct answer is A: Anthrax. The clinical presentation of painless necrotic ulcers with black eschar, along with the gram-positive spore-forming bacilli seen on Gram's staining, is classic for cutaneous anthrax. Anthrax is caused by Bacillus anthracis, which produces spores and can lead to skin lesions in individuals working with animals or animal products. Choice B, Chickenpox, typically presents with vesicular rash all over the body. Choice C, Syphilis, is caused by Treponema pallidum and does not present with the characteristic eschar seen in the patient. Choice D, Tularemia, caused by Francisella tularensis, presents with ulceroglandular lesions but lacks the black eschar characteristic of anthrax.
During the skill-building session in microbiology the students need to stain the prepared and fixed sputum smears obtained from a tuberculosis patient. What staining technique should be used in this case?
- A. Gram
- B. Giemsa
- C. Ziehl-Neelsen
- D. Burri
Correct Answer: C
Rationale: The correct staining technique for sputum smears obtained from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses carbol fuchsin dye to stain the acid-fast bacteria, such as Mycobacterium tuberculosis, red. Here's a step-by-step rationale:
1. Ziehl-Neelsen staining is specifically designed to detect acid-fast bacteria like Mycobacterium tuberculosis.
2. Carbol fuchsin dye is used to penetrate the mycolic acid layer in the cell wall of the bacteria, making them resistant to decolorization.
3. Acid-alcohol is used as a decolorizer to remove the stain from non-acid-fast bacteria.
4. Methylene blue is used as a counterstain to visualize non-acid-fast bacteria in blue.
Therefore, Ziehl-Neelsen staining is the most appropriate technique for identifying Mycobacterium tuberculosis in sputum smears.
Other choices like Gram, Giemsa, and