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Chapter 30. Infectious Diseases

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An otherwise healthy, 75-year-old woman sustained a left ankle fracture and underwent an open reduction internal fixation 4 days ago. She received cephalexin for 4 days after surgery. She subsequently develops diarrhea and mild diffuse abdominal pain. Her white blood cell (WBC) count is 14.2 × 109 cells/L. Stool studies are pending. What is the most appropriate initial treatment regimen?

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A. Oral metronidazole

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B. Intravenous metronidazole

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C. Intravenous vancomycin

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D. Fecal transplantation

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E. Use of as-needed loperamide

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A. Based on this patient’s clinical presentation and history of antibiotic exposure, the most likely diagnosis is Clostridium difficile infection. First-line therapy for mild to moderate C difficile infection is oral metronidazole because it is effective and cost efficient, although oral vancomycin is an acceptable alternative. Intravenous metronidazole is not recommended for monotherapy. Intravenous vancomycin is not a treatment modality for C difficile infection as it does not achieve detectable levels throughout the colon. Fecal transplantation is generally reserved for severe infection or refractory, treatment-resistant infection. Loperamide is not appropriate treatment in the setting of infectious diarrhea.

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An 85-year-old man who underwent an exploratory laparotomy and patch repair of a perforated duodenal ulcer 8 days ago remains intubated and mechanically ventilated for hypoxemic respiratory failure. He is febrile, and his WBC count is 17 × 109 cells/L. The bedside nurse notes copious, thick respiratory secretions. Respiratory cultures are pending. Based on this presentation, what is the most likely causative agent?

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A. Streptococcus pneumoniae

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B. Klebsiella pneumoniae

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C. Staphylococcus aureus

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D. Mycoplasma pneumoniae

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E. Enterococcus faecalis

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C. Based on this patient’s clinical presentation, the most likely diagnosis is a ventilator-associated pneumonia (VAP). VAP is the most common healthcare-associated infection in critical care units and is a leading cause of morbidity and mortality. Microorganisms that are responsible for VAPs may differ based on specific intensive care unit (ICU) populations, although the most common etiologic agents are antibiotic-resistant nosocomial organisms. Staphylococcus aureus and Pseudomonas aeruginosa account for a large proportion of VAPs. Klebsiella pneumoniae can cause VAPs, although must less frequently. Streptococcus pneumoniae and Mycoplasma pneumoniae are less frequently associated with VAPs and more frequently the etiologic organisms in community-acquired pneumonia.

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Reproduced from Lee K. The NeuroICU Book. New York, NY: McGraw-Hill 2012. Adapted in part from American Thoracic Society, Infectious Diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated ...

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