Journal Review: A nasty strain of VRE transmitted to patients

DNA mutation enables resistance to six drugs

Herrero IA, Issa NC, Patel R. Nosocomial spread of linezolid-resistant, vancomycin-resistant Enterococcus faecium. N Eng J Med 2002; 346:867-869.

The authors report the discovery and subsequent nosocomial transmission of a "superbug" — a strain of linezolid-resistant, vancomycin-resistant Enterococcus faecium that was isolated from seven patients. All isolates carried the vanA gene and were resistant to linezolid (minimal inhibitory concentration [MIC], 16 µg per ml), ampicillin, penicillin, gentamicin, streptomycin, and vancomycin. Fortunately, the strain was susceptible to quinupristin/dalfopristin and the investigational agents oritavancin and tigecycline.

The multidrug-resistant strain was first identified in a liver-transplant recipient whose course was complicated by hepatic-artery thrombosis and an intra-abdominal infection with vancomycin-resistant enterococcus, for which he received linezolid. The strain was subsequently nosocomially transmitted to six other patients, none of whom had overt linezolid-resistant, vancomycin-resistant enterococcal infections or had been treated with linezolid.

Five of the six patients were hospitalized in the same transplantation unit as the index patient. Only private rooms were available in this unit, and all health care workers entering the patients’ rooms were required to wear gloves. After the identification of carriers of vancomycin-resistant enterococci, all personnel entering the patients’ rooms were required to wear gloves and gowns.

In preclinical studies, linezolid was active against all enterococci tested. In the isolates the researchers identified, resistance to linezolid was associated with a DNA mutation that previously had been described in linezolid-resistant, laboratory-derived mutant strains of E. faecalis (but not E. faecium). "The emergence of linezolid-resistant, vancomycin-resistant E. faecium as a result of selective pressure is of concern," the authors conclude. "The spread of this multidrug-resistant organism in health care settings is of even greater concern. Our results suggest that the susceptibility of vancomycin-resistant enterococci to linezolid should be determined if the use of linezolid therapy is anticipated, that linezolid should be used prudently, and that there is an ongoing need for the development of agents that are active against vancomycin-resistant enterococci."