Nokea
Bacteria associated with hospital-acquired infections:
- A. Streptococcus pneumoniae
- B. Pseudomonas aeruginosa
- C. Vibrio cholerae
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is commonly associated with hospital-acquired infections due to its ability to survive in hospital environments, resist antibiotics, and infect immunocompromised patients. Streptococcus pneumoniae (choice A) is more commonly associated with community-acquired pneumonia. Vibrio cholerae (choice C) causes cholera, a waterborne disease, and is not typically associated with hospital-acquired infections. Choice D is incorrect because Pseudomonas aeruginosa is indeed associated with hospital-acquired infections.
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Chlorhexidine:
- A. Is characterised by strong human toxicity
- B. Belongs to the group of alcohols and is widely used for disinfection of surfaces and sanitary facilities
- C. Belongs to the group of biguanides and is widely used for disinfection hands, skin and mucous membranes
- D. Is a disinfectant with limited application
Correct Answer: C
Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, which are commonly used for disinfecting hands, skin, and mucous membranes.
Step 2: It is known to have broad-spectrum antimicrobial activity against various pathogens.
Step 3: The usage of chlorhexidine in healthcare settings for preoperative skin preparation and surgical hand scrub is well-established.
Step 4: The effectiveness and safety profile of chlorhexidine make it a preferred choice for disinfection purposes.
Summary:
- Option A is incorrect as chlorhexidine is not characterized by strong human toxicity.
- Option B is incorrect as chlorhexidine is not classified as an alcohol and is primarily used for disinfecting hands, skin, and mucous membranes.
- Option D is incorrect as chlorhexidine has a wide range of applications in disinfection, especially in healthcare settings.
What is the structure of the bacterial cell wall?
- A. Peptidoglycan
- B. Lipopolysaccharides
- C. Phospholipids
- D. Chitin
Correct Answer: A
Rationale: The correct answer is A: Peptidoglycan. Bacterial cell walls are composed of peptidoglycan, a unique macromolecule consisting of sugars and amino acids. This structure provides rigidity and protection to the cell. Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria, not in the cell wall. Phospholipids are the main components of cell membranes, not cell walls. Chitin is a structural polysaccharide found in the cell walls of fungi and some algae, not bacteria.
A smear prepared from material obtained from patient with suspected diphtheria contains yellow bacilli with blue grains at their ends. What staining was used in this case?
- A. Ziehl-Nielsen
- B. Kozlovsky
- C. Romanovsky
- D. Loefler
Correct Answer: D
Rationale: The correct answer is D: Loefler. This staining method is used for identifying Corynebacterium diphtheriae, the causative agent of diphtheria. It involves using methylene blue and basic fuchsin to stain the bacteria. The yellow bacilli with blue grains at their ends indicate the characteristic appearance of C. diphtheriae when stained using the Loefler method.
Choice A: Ziehl-Nielsen is used for acid-fast bacteria like Mycobacterium tuberculosis.
Choice B: Kozlovsky is not a standard staining method in microbiology.
Choice C: Romanovsky is used for blood smears to identify malaria parasites.
Which of the following bacteria IS NOT associated with skin infections?
- A. Staphylococcus aureus
- B. Clostridium perfringens
- C. Pseudomonas aeruginosa
- D. Clostridium difficile
Correct Answer: D
Rationale: Correct Answer: D (Clostridium difficile)
Rationale:
1. Clostridium difficile is primarily associated with gastrointestinal infections, particularly antibiotic-associated colitis.
2. Staphylococcus aureus, Clostridium perfringens, and Pseudomonas aeruginosa are commonly associated with skin infections.
3. Staphylococcus aureus can cause impetigo, boils, and cellulitis.
4. Clostridium perfringens can cause gas gangrene.
5. Pseudomonas aeruginosa can cause hot tub folliculitis and swimmer's ear.
Sanitary bacteriological research on water by the membrane filter method revealed two red colonies on a membrane filter (Endo agar) through which 500 ml of analyzed water were passed. Calculate the coli index and coli titer of the analyzed water:
- A. 4 and 250
- B. 2 and 500
- C. 250 and 4
- D. 500 and 2
Correct Answer: A
Rationale: The correct answer is A: 4 and 250. Coli index is calculated by dividing the number of red colonies by the volume of water analyzed, which gives 2 red colonies / 500 ml = 4. Coli titer is the reciprocal of the coli index, so it is 1 / 4 = 250. This indicates the concentration of coliform bacteria in the water sample. Choices B, C, and D are incorrect as they do not follow the correct calculation steps for determining the coli index and coli titer. B has the correct coli index but incorrect coli titer. C and D have the values reversed, leading to incorrect results.