Sulfur granule-negative pulmonary Schaalia odontolytica infection that mimics lung cancer with lack of radiological response to β-lactam therapy: a case report

A 65-year-old man with long-standing type 2 diabetes mellitus and suboptimal glycemic control had 12 months of productive cough and intermittent hemoptysis, according to a case report in BMC Infectious Diseases. Chest computed tomography showed an upper-lobe mass considered highly suspicious for lung cancer. Bronchoscopically collected secretions stained positive by Gram and Grocott methenamine silver methods, but metagenomic next-generation sequencing of bronchoalveolar lavage fluid detected only 79 sequencing reads of Schaalia odontolytica.

The case report describes an atypical pulmonary infection without the classic sulfur granules associated with pulmonary actinomycosis. The patient received four months of guideline-concordant penicillin therapy, yet the lesion showed no measurable reduction on imaging. Following multidisciplinary discussion and positron emission tomography-computed tomography to characterize the disease and identify other suspicious lesions, he underwent video-assisted thoracoscopic surgery with right upper lobectomy. Intraoperative pus culture and repeated high-abundance metagenomic sequencing confirmed S. odontolytica.

After surgery, the patient received an additional 24 weeks of oral amoxicillin-clavulanate. At six-month follow-up, the report states that he remained clinically and radiologically free of recurrence. The investigators concluded that combining special histochemical staining with metagenomic sequencing may assist diagnostic evaluation in sulfur granule-negative pulmonary actinomycosis that resembles lung cancer. They also reported that a low number of sequencing reads in bronchoalveolar lavage fluid did not exclude invasive infection complicated by an encapsulated abscess in this case.

These findings come from a single case and therefore do not establish the reliability of the diagnostic approach, define optimal timing for surgery, or demonstrate that resection plus prolonged antimicrobial treatment benefits similar patients generally. The case involved one patient with diabetes and a persistent pulmonary lesion initially considered highly suspicious for malignancy. Based on the available abstract, the proposed role of timely surgical resection and prolonged postoperative antimicrobial therapy remains limited to the selected case presented rather than validated as a broader treatment strategy.

Subject of Research: A single case of sulfur granule-negative pulmonary Schaalia odontolytica infection mimicking lung cancer.

Article Title: Sulfur granule‑negative pulmonary Schaalia odontolytica infection that mimics lung cancer with lack of radiological response to β‑lactam therapy: a case report

Article References: Li, G., Ye, B., Zhou, X., & Chen, G. (2026). Sulfur granule‑negative pulmonary Schaalia odontolytica infection that mimics lung cancer with lack of radiological response to β‑lactam therapy: a case report. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14494-x

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14494-x

Keywords: Schaalia odontolytica, pulmonary actinomycosis, case report, lung cancer mimic, metagenomic sequencing, bronchoalveolar lavage, penicillin therapy, surgical resection, amoxicillin-clavulanate, diabetes mellitus, Sulfur, granule