Dissemination of two international linezolid-resistant Staphylococcus epidermidis clones in Greek hospitals

Sir, The growing number of infections caused by multidrug-resistant Staphylococcus epidermidis has necessitated the use of new antimicrobials, such as linezolid, and enhanced the emergence of linezolid-resistant S. epidermidis strains. To date, mutations of region V of 23S rRNA (G2447T, T2504A, C2534T, G2576T, G2603T and G2631T) have been associated with the expression of linezolid resistance among clinical staphylococcal isolates.1–3 Additionally, the presence of the cfr gene, as well as changes in riboprotein L4, have been detected in linezolid-resistant S. epidermidis.3,4 From October 2008 to October 2009, 26 S. epidermidis isolates exhibiting resistance to linezolid were isolated from blood and central venous catheter cultures from 26 individual inpatients hospitalized in the intensive care units (ICUs) of four tertiary care Greek hospitals [Sismanoglion General Hospital of Athens (hospital A), University Hospital of Patras (hospital B), University Hospital of Larissa (hospital C) and University Hospital AHEPA (hospital D)]. Demographic data (age, gender and location) and clinical information (reason for admission and antibiotic therapy) for each patient were collected. The identification of the isolates to species level was primarily performed using the Vitek II Advanced Expert System (bioMérieux, Marcy l'Étoile, France), followed by a molecular method based on the tuf gene.1 Susceptibility testing was performed using the Vitek II Advanced Expert System. MICs of oxacillin, vancomycin, teicoplanin, linezolid, dalfopristin and tigecycline were determined using the CLSI microdilution method and Etest (Biodisk, Solna, Sweden).5