B73-30 Cavitating Lung Nodules Caused by Delftia Acidovorans in an Immunocompetent Patient

Abstract Introduction Cavitating lung nodules represent a distinctive radiologic finding characterized by areas of central necrosis within pulmonary nodules, resulting in cavity formation. While cavitation may occur in various pulmonary diseases, its presence often narrows the differential diagnosis and carries important diagnostic and prognostic implications. The potential etiologies include infectious causes—such as Mycobacterium tuberculosis, Staphylococcus aureus, and fungal infections—as well as non-infectious conditions, including vasculitis (notably granulomatosis with polyangiitis), malignancies (particularly squamous cell carcinoma and metastatic disease), and certain autoimmune or inflammatory disorders. Case Presentation A 75-year-old man was referred to the Rapid Access Lung Cancer Clinic (RALC) following significant unintentional weight loss and an abnormal CT thorax. He reported a weight loss of approximately one stone over one month, without associated respiratory or systemic symptoms. His past medical history was notable for heavy smoking and severe obstructive lung disease confirmed on pulmonary function testing.The CT thorax demonstrated two cavitating lesions in the left lower lobe, measuring 13 mm and 16 mm, along with mildly enlarged left and right lower paratracheal lymph nodes measuring approximately 12-13 mm. The findings were discussed at a multidisciplinary radiology meeting, and an endobronchial ultrasound-guided fine-needle aspiration (EBUS-FNA) of the ATS station 4L lymph node was recommended.Cytological examination revealed benign cells. However, microbiological cultures grew Streptococcus salivarius group and Delftia acidovorans. Based on these findings, the patient was commenced on appropriate antibiotic therapy, with subsequent clinical and radiological improvement. Discussion Delftia acidovorans is an aerobic, non-fermentative Gram-negative bacillus rarely isolated from clinical specimens. Its clinical significance remains uncertain due to infrequent recovery and presumed low virulence. (1) Infections have primarily been described in immunocompromised individuals, particularly those with malignancy, on haemodialysis, or with indwelling medical devices. In immunocompetent patients, reported cases are uncommon and usually linked to intravenous drug use or environmental exposure. (2)D. acidovorans is widely distributed in soil and water, including hospital water systems, and is notable for its resistance to certain disinfectants such as chlorhexidine, facilitating persistence in healthcare environments. (3)Our patient was immunocompetent and had no evident environmental exposure, making this an unusual presentation. The case underscores the importance of considering rare environmental organisms in the differential diagnosis of cavitating pulmonary lesions and the value of thorough microbiological evaluation to guide targeted therapy. Conclusion Cavitating lung nodules caused by D. acidovorans are exceptionally rare, especially in immunocompetent individuals. Prompt recognition, multidisciplinary discussion, and appropriate antimicrobial therapy are key to achieving a favourable outcome. This abstract is funded by: None