A Rare Case of Gulosibacter massiliensis Complicating Peritoneal Carcinomatosis.

BACKGROUND: Gulosibacter massiliensis, a Gram-positive, strictly aerobic, and peroxidase-positive bacterium with high motility, was first isolated from a bloodstream infection in 2022. At present, clinical reports on G. massiliensis are limited, with only one case of skin and soft tissue infection reported, and its pathogenicity and infectivity are still unclear.

CASE PRESENTATION: A 74-year-old male patient with extensive peritoneal carcinomatosis with ascites infected by G. massiliensis. The patient was admitted to the hospital due to confusion of consciousness. After B-ultrasound, ascites cytology, laboratory testing and multi-department joint diagnosis, it was found that he had malignant ascites, G. massiliensis infection, hepatic encephalopathy, peritoneal secondary malignant tumor and other diseases. During the hospitalization, due to the patient's critical condition. The patient was deemed unfit for curative treatment and was managed with best supportive care. Ultimately, respecting the family's wishes, the patient left hospital and went home to receive palliative care. During the laboratory test, we used traditional biochemical reactions and matrix-assisted laser desorption ionization time-of-flight mass spectrometry failed to accurately identify the strain. Finally, the bacteria were finally identified as G. massiliensis by 16S rRNA gene sequencing and NCBI database alignment, and the drug susceptibility results of the bacteria were determined according to the evolutionary relationship and CLSI M45.

CONCLUSION: This study is the first report that G. massiliensis can cause ascites infection as an opportunistic pathogen in immunocompromised patients. It provides a reference for clinical laboratories to identify this rare pathogen and develops anti-infection programs and also points out the research direction for analyzing its pathogenic mechanism.