A 65 year-old man presents to the hospital with a one week history of malaise, headache, fever,

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A 65 year-old man presents to the hospital with a one week history of malaise, headache, fever, and chills. He is admitted and over the next week his disease progressed with a worsening cough and shortness of breath. His physical was benign except for pulmonary compromise. The patient is current on all of their vaccinations and has no recent travel history. A chest radiograph showed multilobar infiltrates. Other significant laboratory findings include an elevated white blood cell count with increased polymorphonuclear neutrophils. Because the patient had a prior history of drug abuse and alcoholism, a toxicology screen and HIV serology were performed. Both were negative. A bronchoscopy was performed, with a bronchoalveolar lavage (BAL) showing many white blood cells, but no organisms. Calcofluor white stains for fungi and direct fluorescent-antibody stain (DFA) for Pneumocystis were also negative. Routine bacterial culture of the BAL was negative.

Why was the BAL routine bacterial culture negative? The patients condition is not due to a microorganism O The pathogen is n