A 24-year-old previously healthy man comes to the office due to a week of low-grade fever, malaise, sore throat, and persistent nonproductive cough. He does not use tobacco, alcohol, or illicit drugs. The patient takes no medications and has no drug allergies. He lives in Connecticut and has not traveled recently. Physical examination reveals mild pharyngeal erythema, no nasal congestion, and bilateral vesicular breath sounds with no crackles or wheezes. Chest x-ray shows patchy, interstitial infiltrates. Sputum Gram stain shows numerous leukocytes but no organisms. Which of the following agents is the best initial treatment for this patient?

Question

A 24-year-old previously healthy man comes to the office due to a week of low-grade fever, malaise, sore throat, and persistent nonproductive cough.  He does not use tobacco, alcohol, or illicit drugs.  The patient takes no medications and has no drug allergies.  He lives in Connecticut and has not traveled recently.  Physical examination reveals mild pharyngeal erythema, no nasal congestion, and bilateral vesicular breath sounds with no crackles or wheezes.  Chest x-ray shows patchy, interstitial infiltrates.  Sputum Gram stain shows numerous leukocytes but no organisms.  Which of the following agents is the best initial treatment for this patient?

Quizplus · Accepted Answer

This patient with low-grade fever, sore throat, persistent cough, and chest x-ray evidence of a bilateral patchy infiltrate likely has "walking pneumonia", a form of atypical pneumonia usually caused by Mycoplasma pneumoniae or Chlamydia pneumoniae. Unlike most bacteria, Mycoplasma and Chlamydia do not have cell walls composed of peptidoglycan. Mycoplasma completely lacks a cell wall, while Chlamydia has a cell wall composed of an alternate protein. Therefore, these pathogens cannot be seen on Gram stain (which stains peptidoglycan) and cannot be treated with antibacterial agents that target peptidoglycan such as penicillins, cephalosporins, vancomycin, or carbapenems (Choice B). Treatment requires a bacterial protein synthesis inhibitor such as a macrolide or tetracycline. Legionella pneumophila is another common cause of atypical pneumonia. However, this pathogen usually is associated with gastrointestinal symptoms (eg, diarrhea), more severe clinical illness (eg, high fever), and lobar infiltrate on chest x-ray. (Choice A) Trimethoprim and sulfamethoxazole are folate metabolism antagonists. They are the first-line therapy for Pneumocystis pneumonia, which often presents with subacute pulmonary symptoms and a bilateral patchy interstitial infiltrate. However, most patients have significant shortness of breath and nearly all are immunocompromised (eg, AIDS, chronic steroids). (Choice D) Azole medications (eg, fluconazole) inhibit the synthesis of ergosterol, a primary component of the fungal cell membrane. Fungal pneumonias are often associated with lobar, nodular, or cavitary infiltrates. However, most occur in the setting of immunosuppression, and an accompanying sore throat would be unusual. (Choice E) Mycolic acid is found in the cell wall of Mycobacterium and can be targeted by isoniazid, a mycolic acid synthesis inhibitor. Active pulmonary tuberculosis often presents with several weeks of cough, weight loss, malaise, and upper lobe cavitary infiltrates. Educational objective: Mycoplasma pneumoniae is a leading cause of atypical pneumonia. Because this pathogen lacks a cell wall, it does not show up on Gram stain and cannot be treated with beta-lactam antibiotics. Protein synthesis inhibitors (eg, macrolides, tetracycline) are the treatment of choice.

A 24-Year-Old Previously Healthy Man Comes to the Office Due