Nokea
The most common bacterial species in hospital environment is:
- A. Borrelia burgdorferi
- B. Staphylococcus aureus
- C. Bacillus cereus
- D. Staphylococcus haemolyticus
Correct Answer: B
Rationale: The correct answer is B: Staphylococcus aureus. This bacterium is commonly found in hospital environments due to its ability to colonize human skin and mucous membranes. It is a leading cause of hospital-acquired infections. Borrelia burgdorferi is mainly associated with Lyme disease transmitted by ticks, not commonly found in hospitals. Bacillus cereus is a foodborne pathogen, not typically prevalent in hospital settings. Staphylococcus haemolyticus is a coagulase-negative staphylococcus species, less pathogenic and less common in hospitals compared to Staphylococcus aureus.
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A patient with a sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic on blood agar. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step 1: Gram-positive cocci in chains suggest Streptococcus species.
Step 2: Catalase-negative eliminates Staphylococcus aureus.
Step 3: Beta-hemolytic on blood agar matches Streptococcus pyogenes.
Step 4: Streptococcus pyogenes is a common cause of sore throat (pharyngitis).
Summary:
A: Streptococcus pyogenes - Correct due to Gram-positive cocci in chains, catalase-negative, beta-hemolytic, and common cause of sore throat.
B: Staphylococcus aureus - Incorrect due to catalase-positive.
C: Streptococcus pneumoniae - Incorrect due to alpha-hemolytic.
D: Enterococcus faecalis - Incorrect due to not being beta-hemolytic.
Which of the following bacteria can produce endotoxins that cause septic shock?
- A. Escherichia coli
- B. Salmonella enterica
- C. Pseudomonas aeruginosa
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all of the mentioned bacteria (Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa) are gram-negative bacteria that produce endotoxins in their cell walls. Endotoxins are released when the bacteria are destroyed, leading to the activation of the immune system and potentially causing septic shock. Escherichia coli and Salmonella enterica are common causes of gastrointestinal infections, while Pseudomonas aeruginosa is known for causing infections in immunocompromised individuals. Therefore, all three bacteria can produce endotoxins that contribute to septic shock. Choices A, B, and C are incorrect because each of these bacteria individually can produce endotoxins that lead to septic shock.
The most important mechanism of tetracycline resistance is
- A. Reduced active influx by alteration of transport molecules
- B. Reduced passive influx due to altered cell membrane components
- C. Increased active efflux from the bacterial cell
- D. Direct enzymatic inactivation of the antibiotic
Correct Answer: C
Rationale: The correct answer is C: Increased active efflux from the bacterial cell. This is the most important mechanism of tetracycline resistance because it involves the bacteria actively pumping out the antibiotic, reducing its intracellular concentration. This prevents tetracycline from effectively targeting bacterial ribosomes. Choice A is incorrect as tetracycline resistance typically involves active efflux rather than reduced influx. Choice B is incorrect because tetracycline resistance mechanisms do not primarily involve altered cell membrane components affecting passive influx. Choice D is also incorrect as tetracycline resistance mechanisms do not typically involve direct enzymatic inactivation of the antibiotic.
Formic acid is a fermentation product of
- A. Streptococcus.
- B. Klebsiella.
- C. Clostridium.
- D. Actinomyces.
Correct Answer: D
Rationale: Step 1: Formic acid is produced during fermentation by Actinomyces.
Step 2: Actinomyces are known to produce organic acids like formic acid through fermentation.
Step 3: Other choices like Streptococcus, Klebsiella, and Clostridium are not typically associated with formic acid production.
Step 4: Actinomyces is the most likely candidate based on its fermentation capabilities.
Summary: Actinomyces is the correct answer because it is known to produce formic acid during fermentation, while the other choices lack this specific metabolic function.
Transmissible spongiform encephalopathies are caused by
- A. flavoviruses.
- B. virusoids.
- C. prions.
- D. orthomyxoviruses.
Correct Answer: C
Rationale: The correct answer is C: prions. Prions are misfolded proteins that can cause transmissible spongiform encephalopathies like Creutzfeldt-Jakob disease. Prions are not viruses like flavoviruses (A) or orthomyxoviruses (D). Virusoids (B) are small, circular, single-stranded RNA molecules that require a helper virus to replicate and are not associated with transmissible spongiform encephalopathies. Therefore, the correct answer is C as prions are the only choice that correctly links to the etiology of transmissible spongiform encephalopathies.