A 30-year-old male with no past medical history presented to the emergency department reporting three weeks of progressively worsening cough producing yellow sputum, pleuritic right scapular pain, four days of fever (to 38.9 C), and one episode of night sweats. Additionally, he noted a ten-pound weight loss, which he attributed to decreased appetite. He denied hemoptysis, shortness of breath, diarrhea, or dysuria. The patient had recently completed a five-day course of azithromycin and had been using benzonatate without relief.
In the two months prior to his presentation, he traveled through Japan, Cambodia, Thailand, Laos, and Israel. He took antimalarial medications when appropriate and had received all required travel vaccinations prior to departing. Additionally, one month before presentation, he had attended Burning Man, an artistic gathering in the middle of the Black Rock Desert in Nevada. His fiancee had traveled with him and was also experiencing a similar but less severe cough. They used a single-room humidifier nightly while sleeping. He had no history of recurrent or severe infections. He denied tobacco or alcohol use. He had a history of occasional marijuana use but denied any intravenous drug use. He worked as a teacher.
On physical exam, his blood pressure was 140/69 mmHg with a pulse rate of 84/min. His tympanic temperature was 36.5 C. His respiratory rate was 18/min, and oxygen saturation on room air was 99%. He was in no acute distress, and examination of his chest was clear to auscultation bilaterally. Laboratory results showed a leukocytosis (WBC 11.3 x 103/muL, 11.2%) without eosinophilia, an elevated venous blood lactate (3.3 mmol/L), and anemia (hemoglobin 12.9 g/dL). His initial chest x-ray was abnormal, so a CT chest with contrast was obtained, which demonstrated a 2.9 cm right upper lobe cavitary lesion (Figure 1(a)). A brief workup for immunodeficiency was then performed. The patient had a negative 4th generation HIV antigen-antibody test as well as a negative HIV RNA PCR. His CD4 count was not measured, but quantitative immunoglobulin analysis was within normal limits (IgG 875 mg/dL, IgA 186 mg/dL, and IgM 76 mg/dL). Quantiferon TB Gold was negative.
Given his clinical stability, failure of outpatient antibiotics, and inability to produce an adequate sputum sample for Gram stain, the decision was made to proceed with bronchoscopy. Bronchoscopy showed diffuse inflammation with mild thick yellow secretions. Cultures of bronchoalveolar lavage, washings, and tissue culture performed during bronchoscopy resulted with heavy growth of P. aeruginosa (Figure 1(b)). No other pathogens were identified. Fungal culture showed no growth after four weeks. Blood cultures, three Kinyon smears of sputum, and urine Legionella antigen were also negative. Aspergillus galactomannan antigen and (1-3)-beta-D-glucan assay (Fungitell) were negative. Histoplasma urine antigen, serum cryptococcal antigen, and serum coccidioides antigens were not detected. Echinococcus antibody was not detected. Once Gram-negative bacilli were identified on cultures, he was treated with ceftazidime (1g q8h IV). The dose was increased to 2g q8h IV after speciation, and sensitivities became available. On this regimen, his condition steadily improved. He was subsequently transitioned to oral ciprofloxacin (750 mg BID for 14 days) and discharged with outpatient follow-up. He completed a 21-day antibiotic course in total.
The identification of P. aeruginosa as the etiologic agent of this otherwise healthy patient's chronic cough and CT chest findings prompted a review of his history for possible exposures to contaminated water. According to the patient, he had three significant exposures to aerosolized water in the past few months: nightly use of a humidifier while sleeping, being sprayed with water at Burning Man, and swimming near a waterfall in Southeast Asia. We asked the patient's family to bring his ultrasonic cool-mist humidifier from home. It was noted to have a thin gray-green film coating the plastic covering as well as standing water in the basin (Figure 1(c)). The patient was unsure when the unit had last been cleaned.
We obtained cultures of the humidifier water and basin, which both returned positive for P. aeruginosa (Figure 1(d)). Humidifier and patient isolates had identical patterns of antibiotic sensitivities. We performed whole genome sequencing (PacBio RSII) on the isolates obtained from the humidifier basin and from the bronchoscopy tissue. We found the isolates to be identical (accessions: NTGC01000000-NTGD01000000).