SAN FRANCISCO — While non-obese patients with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia respond to both of the antibiotics vancomycin and linezolid, obese patients are best treated with linezolid, according to a VA researcher.

Presenting at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy, Aisling Caffrey, PhD, of the Providence, RI, VAMC said her research, part of a larger study on the two drugs, is important because of the growing problem of obesity.1

A retrospective analysis compared outcomes with the two drugs in a VA population admitted with MRSA pneumonia between January 2002 and September 2010. Most of the patients, 2,859, were treated with vancomycin, with another 179 patients treated with linezolid. About 15% of each group was obese, defined as a body mass index of at least 30.

Using proportional-hazard methods, the researchers reviewed treatment outcomes — 30-day mortality, rates of discharge from hospital and intensive care, readmission for both MRSA and non-MRSA causes and intubation.

When investigators looked at discharge from hospital or intensive care by Day 14 without death, treatment change, readmission, ICU admission or intubation, they found that obese patients did notably better on linezolid, with an adjusted odds ratio of 1.77, which had a 95% confidence interval from 1.18 to 2.64.

The non-obese patients showed no significant differences, except that their risk for 30-day readmission was lower with linezolid.
A limitation of the study was lack of information about weight adjustment for vancomycin.

1. Caffrey A, et al “Comparative effectiveness of linezolid and vancomycin stratified by obesity status among a National Veterans Affairs (VA) cohort with methicillin-resistant Staphylococcus aureus (MRSA) pneumonia” ICAAC 2012; abstract K-1628.