Summary A case of a pericarditis with sepsis and multiple subcutaneous abscesses produced by P. aeruginosa was studied. The clinical state of the patient became progressively worse until a situation of prerenal anuria was arrived at, with a maximum tension of 80mmHg, 21,000 white blood cells with neutrophilia and persistent fever peaks. Subcutaneous abscesses then appeared in the lower extremities, from which P. aeruginosa that were sensitive to fosfomycin were isolated, with an MIC of 16 µg/ml. Given the failure of the antibiotic treatment that had been employed up to then, a change was made to fosfomycin (4 g/day intramuscularly), by which a great clinical and analytical improvement was brought about, resulting in the disappearance of the subcutaneous abscesses, which made it possible to surgically operate on the constrictive pericarditis evacuating 1.5 liters of hemorrhagic pericardial fluid in which no P. aeruginosa were isolated. The treatment was continued with the same dose of fosfomycin in both the pre-and postoperatory stage. The posterior evolution of the patient was satisfactory from both the hemodynamic and hepatorenal standpoints.