A 74-year-old man was diagnosed with stage IV squamous cell carcinoma of the right upper lobe of the lung and had started combination immunotherapy. On the day of the third course of the treatment, he developed a fever of 38°C and right-sided chest pain, and was diagnosed with pneumonia of the right upper lobe based on chest computed tomography. Ampicillin/sulbactam was initiated, but a sputum smear specimen showed Gram-negative bacilli, so the ampicillin/sulbactam was switched to ceftriaxone with consideration of drug susceptibility. Subsequently, Shewanella spp. were detected in sputum culture, and the species was identified as Shewanella algae by mass spectrometry. The pneumonia improved with no problems. Pneumonia caused by Shewanella spp. is rare but often takes time to identify, and caution should be exercised during lung cancer treatment because of the risk of fulminant infection.

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An 80-year-old female was admitted with a chief complaint of weight loss. CT revealed a 6 cm mass in the right middle lobe, and bronchoscopic examination showed Actinomyces colonies within the purulent exudate accompanied by neutrophils, leading to a diagnosis of pulmonary actinomycosis. Treatment initially involved intravenous ampicillin/sulbactam followed by oral amoxicillin, which was continued for 10 months. Follow-up CT scan 8 months later demonstrated a reduction of the mass to 2 cm. Pulmonary actinomycosis can rarely present as a pulmonary mass, necessitating prolonged treatment with instances requiring surgical resection reported in the literature.

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