Immunomodulatory effects of fosfomycin in an endotoxin model in human blood.

Objectives: Although a wide range of therapeutic strategies have been developed to improve the outcome of severe sepsis, a convincing reduction in mortality is lacking. Recently, increasing attention has been paid to immunomodulatory effects of antimicrobials. This study set out to explore the immunomodulatory effects of fosfomycin, a broad-spectrum antibiotic frequently used in septic patients, at the protein and molecular levels in vitro.

Methods: Whole blood from 11 healthy volunteers was incubated with 50 pg/mL endotoxin and 100 microg/mL fosfomycin or physiological sodium chloride for 4 h. Real-time RT-PCR was performed for various pro- and anti-inflammatory cytokines. Concentrations of tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 in the supernatant were measured using a commercially available ELISA.

Results: Incubation of human leucocytes with endotoxin increased messenger RNA (mRNA) levels of cytokines several thousand fold compared with baseline. The addition of fosfomycin significantly inhibited mRNA levels of pro-inflammatory cytokines such as IL-1-alpha, IL-6 and TNF-alpha after 2 h (P < 0.01), while no significant reduction was observed for the anti-inflammatory cytokines IL-4, IL-10 and IL-13 (P = 0.26). At the protein level, the concentrations of IL-6 and TNF-alpha increased approximately 3000- and 600-fold after 4 h of incubation with lipopolysaccharide as compared with baseline, respectively. Addition of fosfomycin significantly reduced cytokine levels by 56% and 73% for IL-6 and TNF-alpha, respectively.

Conclusions: Fosfomycin extensively decreased mRNA levels and release of pro-inflammatory cytokines in human blood. The broad antimicrobial coverage of fosfomycin and its immunosuppressive effects could be clinically useful in patients with sepsis.