1. A patient presents with a wound infection, and a Gram stain reveals
gram-positive cocci in clusters. Which organism is most likely
responsible, and what is the rationale for antibiotic therapy?
- A) Staphylococcus aureus; produces exotoxins and has a high
prevalence in skin infections.
- B) Streptococcus pyogenes; commonly associated with throat
infections.
- C) Enterococcus faecalis; typically found in the gastrointestinal tract.
- D) Staphylococcus epidermidis; part of the normal skin flora.
Answer: A) Staphylococcus aureus; it is the most common cause of
wound infections due to its ability to produce exotoxins and its prevalence
in skin infections, making it a critical target for antibiotic therapy.
2. During a tuberculosis outbreak, a nursing student asks why
Mycobacterium tuberculosis is difficult to treat. Which of the following is
the most accurate response?
- A) It has a slow generation time, leading to delayed symptom
presentation.
- B) It forms spores, which are resistant to environmental stresses.
- C) It possesses a mycolic acid cell wall, contributing to antibiotic
resistance.
- D) It is an obligate anaerobe, complicating treatment options.
Answer: C) It possesses a mycolic acid cell wall, which is waxy and
impermeable to many antibiotics, making treatment difficult and
prolonged.
3. A 65-year-old patient with pneumonia has a sputum sample positive for
gram-negative rods. Which pathogen is most likely, and what is the firstline treatment?
- A) Haemophilus influenzae; ampicillin.
- B) Klebsiella pneumoniae; ceftriaxone.
- C) Pseudomonas aeruginosa; ciprofloxacin.
- D) Escherichia coli; trimethoprim-sulfamethoxazole.
Answer: B) Klebsiella pneumoniae; it is a common cause of pneumonia
in elderly patients and ceftriaxone is the first-line treatment due to its
effectiveness against gram-negative pathogens.
4. In a case of suspected septicemia, blood cultures are drawn. Why is it
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