A 42-year-old woman is evaluated in the hospital burn unit due to confusion and a change in the appearance of her wounds. Ten days ago, she was hospitalized after sustaining inhalational injury and severe burns to 30% of her total body surface area in a house fire. She has undergone staged excision and grafting of all appropriate areas and is now receiving daily dressing changes. Temperature is 38 C (100.4 F), blood pressure is 110/70 mm Hg, and pulse is 114/min. The patient is alert to person and place but not time. Physical examination shows necrosis and sloughing of skin grafts to the chest that were previously viable and adherent, with erythema of the surrounding skin. Blood cultures are drawn. Which of the following is the most appropriate empiric antibiotic therapy for this patient's condition?

Question

A 42-year-old woman is evaluated in the hospital burn unit due to confusion and a change in the appearance of her wounds.  Ten days ago, she was hospitalized after sustaining inhalational injury and severe burns to 30% of her total body surface area in a house fire.  She has undergone staged excision and grafting of all appropriate areas and is now receiving daily dressing changes.  Temperature is 38 C (100.4 F), blood pressure is 110/70 mm Hg, and pulse is 114/min.  The patient is alert to person and place but not time.  Physical examination shows necrosis and sloughing of skin grafts to the chest that were previously viable and adherent, with erythema of the surrounding skin.  Blood cultures are drawn.  Which of the following is the most appropriate empiric antibiotic therapy for this patient's condition?

Quizplus · Accepted Answer

Explanation: This patient with severe burn injuries now has necrosis and sloughing of previously viable skin grafts, concerning for burn wound infection (BWI). Burn wounds are quickly colonized with bacteria following the initial injury. Colonization typically does not impair wound healing; however, BWI does. Wound infection is defined as a bacterial count of >10⁵ bacteria/gram of tissue on wound biopsy. Clinically, infection should be suspected when there is a change in wound appearance, loss of a viable skin graft, or development of infectious features (eg, erythema) in noninjured surrounding tissue. ⁵ BWIs are categorized into invasive versus noninvasive infections as follows: Invasive wound infections have systemic manifestations (eg, confusion, tachycardia) of infection and, on biopsy, show microbial invasion into unburned tissue. Suspected invasive infection (as in this patient) requires treatment with broad-spectrum antibiotics that include coverage against the 2 most common burn infection pathogens: Pseudomonas aeruginosa and Staphylococcus aureus. First-line therapy uses a combination of either piperacillin-tazobactam or a carbapenem (eg, meropenem), which have a broad spectrum of activity including against gram-negatives (eg, Pseudomonas), and vancomycin, which has excellent activity against methicillin-resistant Staphylococcus aureus (MRSA). Noninvasive wound infections have minimal or no systemic symptoms and no microbial invasion into surrounding healthy tissue. These are treated empirically with narrower-spectrum antibiotics (eg, cefazolin, clindamycin) that target typical gram-positive skin bacteria. (Choice A) Although invasive fungal infections (which Amphotericin B can treat) sometimes occur in burn patients, they are much less common than invasive bacterial infections. Antifungals are typically added to first-line therapy (eg, meropenem and vancomycin) only if fungal invasion is seen on biopsy. (Choice B) Azithromycin and ceftriaxone, which are commonly used to treat community-acquired pneumonia, are effective against many typical and atypical gram-positive and gram-negative bacteria; however, they have minimal efficacy against Pseudomonas or MRSA. (Choice C) Cefazolin provides coverage against many gram-positive bacteria, and metronidazole provides coverage against anaerobic pathogens; however, neither provides adequate coverage against MRSA or Pseudomonas. (Choice D) Ciprofloxacin and metronidazole, which are commonly used to treat colonic conditions (eg, acute diverticulitis), provide good coverage against aerobic and anaerobic gram-negative pathogens. However, they provide minimal or no coverage against common gram-positive skin organisms (eg, S aureus). Educational objective: When invasive infection is suspected in patients with severe burn injuries, empiric antibiotic therapy is required, typically with coverage against both gram-positive skin flora (including methicillin-resistant Staphylococcus aureus) and gram-negative organisms (including Pseudomonas aeruginosa). Piperacillin-tazobactam or a carbapenem, in combination with vancomycin, are common first-line therapy. References: Infection in burns. (http://www.ncbi.nlm.nih.gov/pubmed/26978531) Burn injury. (http://www.ncbi.nlm.nih.gov/pubmed/32054846)

A 42-Year-Old Woman Is Evaluated in the Hospital Burn Unit