Update on prevalence and mechanisms of resistance to linezolid, tigecycline and daptomycin in enterococci in Europe: Towards a common nomenclature.

Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens. Invasive VRE infections are difficult to treat since common therapeutic options including ampicillin and glycopeptides often fail. In vitro, most VRE remain susceptible to last-resort antibiotics such as linezolid, tigecycline and daptomycin. However, neither tigecycline nor linezolid act in a bactericidal manner, and daptomycin has proven activity only at high dosages licensed for treating enterococcal endocarditis. Despite these pharmacological and therapeutic limitations, reports on resistance to these last-resort drugs in VRE, and enterococci in general, have increased in recent years. In this review, we briefly recapitulate the current knowledge on the mode of action as well as the known and novel mechanisms of resistance and describe surveillance data on resistance to linezolid, tigecycline and daptomycin in enterococci. In addition, we also suggest a common nomenclature for designating enterococci and VRE with resistances to these important last-resort antibiotics.

Clonal outbreak of ST17 multidrug-resistant Enterococcus faecium harbouring an Inc18-like::Tn1546 plasmid in a haemo-oncology ward of a Spanish hospital.

OBJECTIVES: To report a clonal outbreak of ST17 vancomycin-resistant Enterococcus faecium (VREfm) carrying Tn1546 (vanA) in a haemo-oncology ward of a tertiary teaching hospital in the south of Spain (January-September 2009). PATIENTS AND METHODS: Twenty-two VREfm strains from 13 patients were characterized by PFGE, multiple-locus variable-number tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST). Genes encoding antibiotic resistance and putative virulence traits and the Tn1546 backbone were investigated by PCR. Plasmid characterization included determination of size (S1-PFGE) and replication modules (PCR, hybridization and sequencing). Patient clinical records were analysed retrospectively. RESULTS: A single ST17 E. faecium clone (MT-7 MLVA type) carrying esp and hyl plus a 30 kb Inc18-like::Tn1546 (IS1216) plasmid was identified. Ampicillin resistance was linked to PBP5 showing mutations at positions 24, 27, 34, 66, 68, 85, 100, 144, 172, 177, 204, 216, 324, 462, 466', 470, 485, 496, 499, 525, 546, 558, 582, 586, 629, 632, 642 and 667. Other resistance genes identified were erm(B), ant(6')-Ia and aph(3')-IIIa. Fluoroquinolone resistance was attributable to ParC (Arg-61 → Gly and Ser-80 → Arg) and GyrA (Ser-83 → Arg) mutations. CONCLUSIONS: A nosocomial outbreak caused by an ST17 (CC17) E. faecium clone harbouring Esp and Hyl and a 30 kb Inc18-like::Tn1546 plasmid among haemo-oncology patients is reported. The failure of early infection control practices indicates an undetected reservoir and the ability of this strain to persist over long periods. The potential spread of epidemic clones and broad host plasmids carrying vancomycin resistance in Spain is of concern since it might contribute towards a higher rate of VREfm infection.