Fatal Catheter-Related Hematogenous Disseminated MSSA Sepsis in an Immunocompromised Lung Cancer Patient: A Case Report.

PURPOSE: The pathogenicity of Staphylococcus aureus is well-recognized, stemming from its potent toxins and invasive capabilities. However, disseminated infections caused by methicillin-sensitive S. aureus (MSSA) are prone to being overlooked clinically. This study aims to report a case of disseminated invasive infection caused by MSSA in an immunocompromised patient, highlighting the clinical challenges in diagnosis, treatment, and outcomes. CASE PRESENTATION: In October 2022, the patient was found to have a pulmonary nodule (65 × 53 mm); in April 2023, a biopsy confirmed a diagnosis of lung cancer; on November 21, 2024, a PICC line was inserted to administer chemotherapy. After completing chemotherapy, the patient was discharged home, where he gradually developed diarrhea. On December 3, 2024 (12 days after chemotherapy), the patient began experiencing shortness of breath and coughing. The patient presented with septic shock, acute respiratory distress syndrome (ARDS), and acute renal failure. Imaging studies revealed bilateral pulmonary infiltrates; a chest X-ray showed a "white lung" sign, and a CT scan demonstrated multiple nodules and cysts consistent with hematogenous dissemination. Methicillin-sensitive Staphylococcus aureus (MSSA) was detected via tNGS, blood culture, and bone marrow culture. Despite a series of antimicrobial treatments, the infection spread to the bone marrow and spleen. Although the treatment regimen was ultimately adjusted to cefoxitin combined with clindamycin and the symptoms of the infection were brought under control, the persistence of the previous infection and a secondary Enterococcus faecalis infection, combined with the progression of lung cancer, ultimately led to multiple organ failure, and the patient died on day 28. CONCLUSION: MSSA can cause rapidly progressive disseminated infection in immunocompromised patients, even with susceptible strains. Early diagnosis using tNGS and targeted antibiotic therapy are critical. Strict catheter care and infection control measures are essential to prevent such life-threatening complications.