Bacteremia Caused by Linezolid-Resistant Enterococcus faecium in Liverpool, United Kingdom

Linezolid is an effective antimicrobial agent for treating infections caused by vancomycin-resistant enterococci (VRE). More than 99.4% of all Enterococcus faecium isolates are susceptible to linezolid (1). We describe a case of bacteremia caused by a linezolid-resistant E. faecium strain that developed while treating a patient with an intra-abdominal infection. Linezolid acts at the peptidyltransferaseactive site at the 50S ribosome, blocking aminoacyl-tRNA binding and thereby preventing translation initiation. The most common mechanism for linezolid resistance in enterococci is the G2576T mutation, leading to G2576U alteration in domain V of the 23S rRNA, altering the drug’s binding site (2). We performed PCR on our patient’s VRE blood culture isolates to determine the presence of the mutational resistance mechanism, and we determined drug penetration levels into the site of infection by measuring the linezolid concentrations in samples of pancreatic fluid.