A 6-year-old boy is brought to the emergency department with severe shortness of breath. He has had a runny nose for the past week and fever, chills, and productive cough for 2 days. The patient was diagnosed with cystic fibrosis on newborn screening and has had multiple hospitalizations since infancy for respiratory infections requiring intravenous antibiotics. He also had multiple skin infections requiring incision and drainage over the past year. Temperature is 39.4 C (103 F), blood pressure is 90/60 mm Hg, pulse is 130/min, and respirations are 35/min. Pulse oximetry shows a SaO₂ of 85% that improves to 92% after oxygen supplementation. Examination shows nasal flaring, intercostal retractions, and grunting, and auscultation reveals bibasilar crackles and expiratory wheezing. Chest x-ray reveals infiltrates in the right and left lower lobes. Influenza antigen testing is positive. Cefepime and oseltamivir are administered. Which of the following empiric antibiotics should also be administered in this patient?

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11ec25c8_d718_3f15_bc81_fdc583efbc6e_MD0003_00 Pulmonary disease is the primary cause of morbidity and mortality in cystic fibrosis (CF). Defective mucociliary clearance of inspissated secretions permits accumulation of debris and bacteria in the airway, resulting in recurrent sinopulmonary infections. This patient has a severe acute pulmonary exacerbation, as evidenced by hypoxia and respiratory distress (eg, nasal flaring, retractions, grunting). Staphylococcus aureus is the most common pathogenic organism in young children with CF, especially in the setting of concurrent influenza infection. Empiric antistaphylococcal antibiotics should be administered immediately and intravenously in patients with severe pneumonia. Cefepime, a fourth-generation cephalosporin, provides coverage for both methicillin-sensitive S aureus (MSSA) and Pseudomonas aeruginosa. Methicillin resistance should also be anticipated in this patient, given his history of recurrent hospitalizations, recurrent skin abscesses, and concurrent influenza infection. Intravenous vancomycin is therefore the most empiric antibiotic choice. (Choice A) Itraconazole and voriconazole are the preferred antifungals for chronic pulmonary aspergillosis. Older children and adults with CF are often colonized and infected by Aspergillus fumigatus, but fungal disease is less common in young children. (Choice B) Nafcillin is an intravenous beta-lactam antibiotic with activity against MSSA and Streptococcus pneumoniae. Given that cefepime provides adequate MSSA coverage for this patient, nafcillin would be an inappropriate choice as it does not provide additional coverage for methicillin-resistant organisms. (Choice D) High-dose oral amoxicillin is the drug of choice for the outpatient treatment of community-acquired pneumonia for coverage of S pneumoniae. It does not cover S aureus. (Choice E) Azithromycin is a macrolide antibiotic typically used in the treatment of pneumonia due to atypical organisms (eg, Mycoplasma pneumoniae). Azithromycin is not used in acute CF exacerbations, but chronic maintenance therapy with azithromycin in patients with CF has been shown to slow lung function decline. (Choice F) Ciprofloxacin is appropriate for the empiric treatment of P aeruginosa, which is the most common cause of pneumonia in adults with CF but is less common in young children. Oral antibiotics would be inappropriate in this patient with severe pneumonia. Educational objective: Staphylococcus aureus is the most common cause of bacterial pneumonia in young children with cystic fibrosis, especially in those with coexisting influenza infection. For patients with severe pneumonia, frequent hospitalizations, or recurrent skin infections, intravenous vancomycin should be included for empiric therapy against methicillin-resistant S aureus. References: Treatment of pulmonary exacerbations in cystic fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/23997047) Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. (http://www.ncbi.nlm.nih.gov/pubmed/21208910) Association between respiratory tract methicillin-resistant Staphylococcus aureus and survival in cystic fibrosis. (http://www.ncbi.nlm.nih.gov/pubmed/20551409)

A 6-Year-Old Boy Is Brought to the Emergency Department with Severe