We report on adjuvant immune-modulating treatment with interferon g (IFN-g) in prolonged disseminated methicillin-sensitive Staphylococcus aureus sepsis, and describe the effects on the immune system using flow cytometry and gene expression profiling of leukocytes before and 5 days after IFN-g. Sepsis is associated with lymphocyte apoptosis (1), impaired antigen presentation (2), and relative increase of T regulatory cells (Tregs)(3), while Staphylococcus can form abscesses and small colony variants, and can survive intracellularly, leading to difficult eradication (4, 5). IFN-g up-regulates human leukocyte antigen complex (HLA-DR) expression on monocytes (2), and activates phagocytosis and microbial killing (6). It has been successfully used to treat septic patients with persistently low expression of HLA-DR on monocytes (2, 7).

A 58-year-old man with type II diabetes was admitted with hyperglycemic hyperosmolar syndrome and shock associated with bacteraemia, pyuria, lung abscesses, and septic polyarthritis, all growing identical strain of Staphylococcus aureus. Despite using appropriate antibiotics, infection persisted without clinical improvement. After 3 weeks, the first of two doses of IFN-g (2 Mio units, 3 days apart) was administered subcutaneously. A short-lived self-limiting inflammatory response followed on both occasions. However, the patient’s clinical condition improved within a week, allowing discharge from ICU and transfer for rehabilitation.