A 56-year-old woman comes to the emergency department due to a week of fever, dyspnea, and cough with productive, foul-smelling sputum. She has no chills or rigors. The patient was seen at an urgent care center for these symptoms 4 days ago, and a 5-day course of azithromycin was prescribed to treat pneumonia. However, she feels worse despite taking the medicine. The patient underwent upper gastrointestinal endoscopy 10 days ago due to a long history of heartburn. Temperature is 38.7 C (101.7 F), blood pressure is 130/80 mm Hg, pulse is 108/min, and respirations are 22/min. Dentition is poor. Crackles are heard over the right upper lung field. There are no cardiac murmurs. The abdomen is soft and nontender. Complete blood count reveals a leukocyte count of 14,500/mm3. Chest x-ray shows a right upper lobe infiltrate. Which of the following antibiotic therapies is most likely to improve her symptoms?
Bacterial aspiration pneumonia | |
Pathophysiology |
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Major risk factors |
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Clinical features |
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Management |
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This patient underwent upper gastrointestinal endoscopy and subsequently developed community acquired pneumonia likely due to bacterial aspiration during the procedure. Upper endoscopy increases the risk of aspiration because the endoscope probe impairs closure of the glottis and lower esophageal sphincter. This can lead to chemical pneumonitis within a few hours due to aspiration of gastric acid or to pneumonia several days later due to aspiration of gastric microbes.
Patients with bacterial aspiration pneumonia usually develop progressive fever, dyspnea, and cough, which may be productive of foul-smelling sputum. Chest imaging usually shows an infiltrate in a dependent portion of the lung; in the recumbent position, the dependent segments are the superior portions of the lower lobes and the posterior portions of the upper lobes. Leukocytosis is often present.
Although early data showed that most cases of aspiration pneumonia were caused by anaerobes (eg, Peptostreptococcus, Fusobacterium), newer evidence indicates that the vast majority of infections are caused by aerobes (eg, gram-negative bacilli, Streptococcus pneumoniae, Staphylococcus aureus) . Therefore, in the absence of lung abscess or empyema, empiric treatment for aspiration pneumonia is the same as for community-acquired pneumonia; this patient who failed azithromycin therapy should be given a broader spectrum agent such as amoxicillin-clavulanate.
(Choice B) Ciprofloxacin provides excellent gram-negative coverage but has limited efficacy against many upper respiratory gram-positive organisms.
(Choice C) Although doxycycline covers atypical organisms in patients with community-acquired pneumonia, it does not have broad enough activity against typical aerobic pathogens to be used as monotherapy.
(Choice D) Metronidazole provides coverage of gram-negative anaerobes but does not adequately cover aerobic pathogens.
(Choice E) Trimethoprim-sulfamethoxazole is the drug of choice for Pneumocystis pneumonia and is effective against many gram-negative and gram-positive microbes; however, it does not provide broad enough coverage for upper respiratory aerobic organisms to be used as empiric treatment for aspiration pneumonia.
Educational objective:
Upper endoscopy increases risk for bacterial aspiration pneumonia. In the absence of lung abscess or empyema, aspiration pneumonia is treated with the same agents as community acquired pneumonia.