An 82 year old man is hospitalized with pneumonia. He was treated with penicillin

An 82 year old man is hospitalized with pneumonia. He was treated with penicillin and discharged after 7 days when his symptoms subsided. Two weeks later, the man was readmitted to the hospital for pneumonia. No bacteria or viruses were cultured from a biopsy specimen. Broad-spectrum antibiotic therapy was administered. The patient developed pneumonia again after returning home from an 8-day hospital stay. A bronchoscopy showed septate hyphae in his lung tissue. An investigation of his home showed that he did not keep pets but some sparrows had nested outside the living room window; he was not a gardener or outdoorsman. Aspergillus was cultured from his humidifier.

1. What is your preliminary identification of the pathogen?
2. Why was the diagnosis delayed?
3. Why did his infection recur?