The growing incidence of infections due to Gram-positive multiresistant germs has stimulated research into new drugs endowed with broader activity, that are useful in case of infections unresponsive to common antibiotics. The case of a 28-year-old man infected with a methicillin resistant Staphylococcus aureus non responder to therapy with glycopeptide antibiotics is reported. At admission the patient presented a septic condition and required mechanical ventilation. Antibiotic therapy was immediately started with teicoplanin+meropenem. Blood culture and bronchial aspirate evidenced a methicillin resistant Staphylococcus aureus with high sensibility to glycopeptide antibiotics. Although this therapy produced a slight improvement in clinical condition and the patient was extubated, fever and leucocytosis associated with a BAL positive to methicillin resistant Staphylococcus aureus, in vitro susceptible to glycopeptides, persisted. Considering the possibility of a non-responder condition of the patient to glycopeptide antibiotics, quinupristin/dalfopristin was added. The streptogramin produced a quick improvement in clinical condition with resolution of sepsis and culture sterilization. The patient improved progressively and was discharged. In conclusion, in our experience the association quinupristin/dalfopristin was effective in the resolution of a critical methicillin resistant Staphylococcus aureus infection non responder to classical treatment with glycopeptide antibiotics that showed a high sensibility in vitro.