Nokea
Which of the following bacteria should be handled in a Biosafety Level 2 facility?
- A. Micrococcus luteus
- B. Bacillus subtilis
- C. Salmonella
- D. Staphylococcus epidermidis
Correct Answer: C
Rationale: The correct answer is C: Salmonella. This bacterium should be handled in a Biosafety Level 2 facility due to its potential to cause disease in humans. Salmonella is a pathogenic bacterium that can cause foodborne illnesses and infections. Handling it in a Biosafety Level 2 facility ensures proper containment and protection of personnel.
A: Micrococcus luteus and B: Bacillus subtilis are common environmental bacteria that do not pose significant risks to human health, so they can be safely handled in lower biosafety levels.
D: Staphylococcus epidermidis is a common skin commensal bacterium that is generally not considered highly pathogenic, so it does not require Biosafety Level 2 containment.
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For Parvovirus B19 it is true that:
- A. Its genome consists of dsDNA
- B. Is an enveloped virus
- C. Has segmented genome
- D. There are three structural proteins
Correct Answer: A
Rationale: Step-by-step rationale for choice A being correct:
1. Parvovirus B19 is a single-stranded DNA (ssDNA) virus.
2. The prefix "parvo-" indicates small size, characteristic of ssDNA viruses.
3. ssDNA viruses replicate in the host cell by converting their ssDNA genome into double-stranded DNA (dsDNA).
4. Therefore, the correct answer is A: Its genome consists of dsDNA.
Summary of why other choices are incorrect:
B: Parvovirus B19 is a non-enveloped virus, making choice B incorrect.
C: Parvovirus B19 has a linear ssDNA genome, not segmented, making choice C incorrect.
D: Parvovirus B19 has two structural proteins - VP1 and VP2, making choice D incorrect.
Which structure protects bacteria from phagocytosis?
- A. Flagella
- B. Capsule
- C. Endospore
- D. Pili
Correct Answer: B
Rationale: The correct answer is B: Capsule. Capsules are a protective layer outside the bacterial cell wall that helps bacteria evade phagocytosis by immune cells. The capsule inhibits phagocytic cells from engulfing the bacteria, making it difficult for them to be recognized and destroyed.
A: Flagella - Flagella are not involved in protecting bacteria from phagocytosis. They are responsible for bacterial movement.
C: Endospore - Endospores are dormant, resistant structures formed by some bacteria in response to harsh conditions. They do not directly protect against phagocytosis.
D: Pili - Pili are hair-like structures used for adhesion and conjugation, not for protection against phagocytosis.
Sanitary important bacteria for control of air quality are:
- A. Alpha and beta-hemolytic streptococci
- B. Pseudomonas aeruginosa
- C. E. Coli
- D. Salmonella spp.
Correct Answer: B
Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is important for controlling air quality as it can degrade a wide range of organic compounds present in the air, helping to maintain a clean and healthy environment. Alpha and beta-hemolytic streptococci (Choice A) are not typically associated with air quality control. E. coli (Choice C) and Salmonella spp. (Choice D) are more commonly found in water and food sources, not air, making them incorrect choices for this question. Pseudomonas aeruginosa's ability to break down organic matter in the air makes it the most suitable option for maintaining sanitary air quality.
How the prepared immunofluorescence slide should be examined?
- A. Under the fluorescence microscope using x100 oil immersion objective
- B. Under light microscope using x100 oil immersion objective
- C. Using electron microscopy
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because immunofluorescence slides are examined under a fluorescence microscope with a x100 oil immersion objective. This is because immunofluorescence relies on the detection of fluorescently labeled antibodies, which emit light when excited by a specific wavelength. Using a fluorescence microscope allows for visualization of these labeled antibodies at high magnification and resolution, enabling precise examination of cellular structures and protein localization. Choice B is incorrect as light microscopes are not suitable for visualizing fluorescence. Choice C is incorrect as electron microscopes use electrons, not light, for imaging, which is not compatible with immunofluorescence. Choice D is incorrect as there is a specific method for examining immunofluorescence slides.
A patient with a sore throat and fever had a throat smear stained with Gram's method, revealing Gram-positive cocci in chains. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium is known to cause sore throat and fever, commonly referred to as strep throat. Gram's stain showing Gram-positive cocci in chains is characteristic of Streptococcus species. Streptococcus pyogenes is a beta-hemolytic bacterium that forms chains and is a common cause of bacterial pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci that forms clusters, not chains. Neisseria gonorrhoeae (C) is a Gram-negative diplococcus and is not associated with sore throat. Enterococcus faecalis (D) is a Gram-positive cocci that can cause infections but is not typically associated with sore throat.