Endemic linezolid-resistant Staphylococcus epidermidis in a critical care unit.

The aim of this article was to report the emergence of patient infections with linezolid-resistant Staphylococcus epidermidis (LRSE) in a tertiary university hospital. Our objectives were to determine the molecular mechanism of the resistance, set up the genetic relationship among isolates, and analyze the relations between linezolid usage, period of treatment, and emergence of resistance in the hospital. The emergence of infection with linezolid-resistant S. epidermidis affecting 20 patients in a tertiary university hospital was investigated using repetitive sequence-based PCR (rep-PCR, DiversiLab System; BioMérieux, Inc., France). The presence of the G2576T mutation of 23S rRNA was screened by pyrosequencing. We determined the pattern of linezolid usage in the hospital as a whole and in the critical care unit that was most affected. G2576T mutation of 23S rRNA was detected in all linezolid-resistant S. epidermidis studied. Of these, 90% were genetically related and had been recovered from patients admitted to the same critical care unit. There had been an increase in linezolid usage in the hospital and in the critical care unit in the 2 years prior to the emergence of resistant strains. More strict control measures in hand washing and linezolid prescription were subsequently established, but no reduction in LRSE rates have yet been observed. Linezolid-resistant S. epidermidis emerged at our hospital, probably from a single strain originating in the critical care unit. The most likely explanation is that person-to-person spread of linezolid-resistant S. epidermidis led to skin colonization and, after linezolid treatment, this resistant staphylococci became the dominant cutaneous flora causing infection in some critical patients. In order to preserve the usefulness of this antibiotic as a therapeutic agent and to avoid a situation similar to methicillin-resistant Staphylococcus aureus, judicious use of antibiotics is essential.