A 72-year-old Japanese female was admitted to Tsukuba University Hospital (Tsukuba, Japan) in September 2015 with aggravation of consolidation in the lingular segment. She had never smoked; however, she had a 36-year history of bronchiectasis in the lower right lobe and lingular segment with several episodes of hemosputum. She also received clopidogrel to maintain a stent inserted for cerebral aneurysm. She had pet cats and slept with them for almost 30 years.
Physical examination at admission was unremarkable. Laboratory findings, including white blood cell count and C-reactive protein levels, were normal. T-SPOT.TB test for tuberculosis and serum anti-Mycobacterium avium complex antibody level was negative. Chest computed tomography (CT) revealed worsened bronchodilation, bronchial wall thickness, centrilobular nodules, and air-space consolidation in the lower right lobe and lingula (Fig. 1A).
Bronchoscopy was performed to confirm the pathogen identity. A large amount of purulent sputum was observed in the lingular segments (Fig. 2A). Cultures of wash specimens from the right B8a and lingular segments revealed gram-negative rods (Fig. 2B), which using Vitek 2 testing, were identified as P. canis with a 91% identification probability. In addition, culturing using MacConkey agar was negative for bacterial growth; isolated bacteria could not dissolve maltose and mannitol, but could dissolve ornithine. These results were consistent with those obtained for P. canis. Because P. canis quite rarely causes pneumonia, we performed 16S ribosomal RNA (rRNA) sequencing for confirming the diagnosis; the isolates were identified as P. multocida subsp. septica with a 99.9% probability (Fig. 2C). Based on these results, P. multocida pneumonia was finally diagnosed. While waiting for the rRNA sequencing analysis results, the patient suffered worsened hemoptysis and was readmitted to our hospital in October (Fig. 1B). Intravenous ampicillin/sulbactam (9.0 g/day) was administered for one week, followed by oral amoxicillin-clavulanic acid (750 mg/day) for another 30 days. After antibiotic therapy, the lower right lobe and lingular shadows were extremely improved (Fig. 1C). She was discharged on day 25 without any complications. Before discharge, we instructed her to strictly wash her hands after contact with her cats; we also instructed her to keep the cats away from her bed. We followed-up with her two years after her discharge, during which she had no symptoms of hemosputum related to pasteurellosis. Written informed consent was obtained from the patient for publication of the case details and associated images.