Clonal spread of linezolid and teicoplanin-resistant Staphylococcus haemolyticus in intensive care unit patients in a tertiary hospital
Abstract number: P1197
Rodriguez Aranda A., Daskalaki M., Villar J., Sanz F., Otero J.R., Chaves F.
Objectives: Following the observation of several cases of infections caused by isolates of linezolid and teicoplanin-resistant S. haemolyticus (LTRSH) we decided to investigate the epidemiology and clonality of these isolates, and to determine the molecular mechanism of resistance to linezolid.
Methods: Medical records of all patients with LTRSH in the last three years were reviewed. Antimicrobial susceptibility testing was performed with Wider panels (Soria-Melguizo, Madrid, Spain) and minimun inhibition contentrations (MIC) were performed by the Etest method for linezolid, teicoplanin, vancomycin, tigecycline and daptomycin. Molecular characterisation of LTRSH isolates was performed by pulsed-field gel electrophoresis (PFGE) after SmaI digestion. A 420bp Domain V region of the 23S gene was amplified for each isolate and the products were digested with NheI restriction enzyme for detecting the G2576T mutation, which has been associated with linezolid resistance.
Results: Between October 2005 and March 2007 we recovered 22 clinical isolates of TLRSH from 15 patients. The mean age was 56 years (SD 11.75) and 66.7% were male. All patients were diagnosed of LTRSH infections while they were in ICU. Fourteen cases were considered clinical infections: 11 catheter-related bacteraemia and 4 surgical infections. Eleven patients underwent abdominal surgery, including four patients with liver transplantation. All isolates were resistant to meticillin, erythromicin, clindamicin, levofloxacin, rifampicin, trimethoprim-sulfamethoxazole, teicoplanin (range 24128 mg/L) and linezolid (range 32 to 128 mg/L) and susceptible to vancomycin, tigecycline and daptomycin. PFGE analysis indicated that all isolates belonged to a single clonal group. All linezolid-resistant isolates had the same 23S rRNA mutation in domain V, G2576U, and the incomplete digestion of NheI indicated that not all copies of rRNA genes carried the mutation.
Conclusion: This report documents the spread and persistence of a single clone of multidrug-resistant S. haemolyticus, including resistance to linezolid and teicoplanin, in ICU patients. This study confirmed previous reports regarding the importance of the G2576T mutation associated to linezolid resistance in Enterococcus faecium, Staphylococcus epidermidis and S. haemolyticus. The emergence of LTRSH in hospitals has important clinical and epidemiological implications.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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