Linezolid Contributes to “Clinical Success” in MRSA Pneumonia

Veterans with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia who were treated with linezolid were 53% more likely to be discharged as “clinical successes,” according to researchers from Providence VAMC and Brown University, both in Providence; and University of Rhode Island in Kingston, all in Rhode Island; and Pfizer Inc. in Collegeville, Pennsylvania.

The researchers conducted a nested case-control study among 3,732 VA patients with MRSA pneumonia who received linezolid or vancomycin between January 2002 and September 2010. They compared a number of factors that might contribute to clinical success, which was defined as discharge from the hospital or intensive care unit (ICU) by day 14 after treatment initiation. The 1,290 control patients represented nonsuccess, defined as therapy change, intubation, admission to ICU, readmission, or death between treatment initiation and day 14. The researchers chose 14 days to replicate the average end-of-treatment time frame in existing clinical trials of linezolid and vancomycin. The potential predictors included treatment, patient demographic and admission characteristics, previous health care and medication, comorbidities, and medical history. The clinical-success patients were more likely to be older (aged 69.5 years vs 68.5 years in the nonsuccess group), have a current diagnosis of respiratory disease, and to have had a diagnosis of pneumonia in the year before the MRSA pneumonia admission.

Only 2 predictors of clinical success were significant: Treatment with linezolid (adjusted odds ratio [OR], 1.53; 95% confidence interval [CI], 1.12-2.10) and previous complication of an implant or graft, including mechanical complications and infections, in the year before admission for MRSA pneumonia (adjusted OR, 1.55; 95% CI, 1.17-2.06). Clinical success also was more likely when the length of therapy was shorter. The researchers were not sure why having an implant or graft complication was associated with clinical success, but they theorize that those instances might have prompted more aggressive treatment.

Predictors with adjusted ORs of < 1 were associated with nonsuccess. These included diagnosis of concomitant urinary tract infection, IV line, previous coagulopathy, previous amputation procedure, current coagulopathy diagnosis, dialysis, multiple inpatient procedures, inpatient surgery, and previous endocarditis.

Of all the variables, the researchers say, only the linezolid treatment was modifiable. However, they note that the few trials that support their findings have been criticized for methodological and statistical flaws. Their study adds to the developing literature, they say, by assessing a large national cohort of patients with MRSA pneumonia and by using objective clinical outcomes. They add that MRSA pneumonia tends to affect patients with complex care, and their findings may help clinicians identify patients who may benefit from alterations in treatment or require additional attention.

Source
Caffrey AR, Morrill HJ, Puzniak LA, LaPlante KL. Clin Ther. 2014;36(4):552-559.
doi: 10.1016.j.clinthera.2014.02.013.