Risk factors and outcomes associated with vancomycin-resistant Enterococcus infections with reduced susceptibilities to linezolid

A retrospective matched case-control study of hospitalized patients with vancomycin-resistant Enterococcus (VRE) infection with reduced susceptibility to linezolid was performed in order to identify risk factors for this infection and describe patient outcomes. Forty-eight linezolid nonsusceptible VRE cases were identified between January 1, 2000, and September 30, 2008, and compared to 96 controls with linezolid-susceptible VRE, matched based on culture date and anatomic site of infection. Demographic, clinical and microbiological data were collected. On univariable analysis, risk factors for reduced linezolid susceptibility included allogeneic hematopoietic stem cell transplant and/or solid organ transplant (odds ratio [OR]: 2.63; 95% confidence interval [CI]: 1.13-6.15; P = 0.025), receipt of immunosuppressive medications (OR: 2.39; 95% CI: 1.08-5.29; P = 0.032) including corticosteroids (OR: 2.40; 95% CI: 1.03-5.58; P = 0.042) and noncorticosteroid immunosuppressives (OR: 2.31; 95% CI: 1.00-5.30; P = 0.049), and receipt of linezolid within 1 year prior to infection (OR: 34.50, 95% CI: 4.60-259.02; P < 0.001). On multivariable analysis, only receipt of linezolid within 1 year remained an independent risk factor for reduced linezolid susceptibility (OR: 31.84; 95% CI: 4.20-241.39; P < 0.001), although most patients with VRE with reduced linezolid susceptibility had not received linezolid in the year prior. Reduced linezolid susceptibility did not impact patient outcomes including clinical or microbiological cure, hospital length of stay, or all-cause mortality.