Usefulness of linezolid in the treatment of hospital-acquired pneumonia caused by MRSA: a prospective observational study.

Clinical results for linezolid (LZD) treatment of hospital-acquired pneumonia (HAP) caused by methicillin-resistant Staphylococcus aureus (MRSA), particularly microbiologically evaluable or severe cases, are limited in Japan. A prospective observational study was conducted in order to assess the usefulness of LZD in Japanese patients with MRSA pneumonia. The study tracked fifteen participants treated with LZD for pneumonia who met the criteria of the HAP guidelines and were confirmed to have pneumonia caused by MRSA. Of these, six were severe and 13 had received antibiotic treatment before treatment with LZD. Of the 13 participants assessed for their clinical responses, seven were rated as cures, three were rated as failures, and three were indeterminate. The overall cure rate (cure/cure + failure) was 70.0% (7/10), and the cure rate by severity was 33.3% (1/3) for severe cases and 85.5% (6/7) for moderate cases. The one severe case with a clinical response rating of cure had failed to respond to vancomycin. Among the seven participants with a clinical response rating of cure, the microbiological response was eradication in three, presumed eradication in three, and indeterminate in one. Three serious adverse events occurred in two of the 15 participants, but none were considered to be causally related to LZD. The results suggest that LZD has high potential for severe and multidrug-resistant cases. A higher cure rate was achieved in moderate cases. In cases of pneumonia that are most likely MRSA infections with poor prognosis, it was suggested to be important for patient outcome to implement the most effective therapy before the patient's condition becomes serious.