Crucell has discovered potent human monoclonal antibodies (mAbs), which neutralize Enterococcus in an animal model. These mAbs are currently being investigated in further preclinical studies.

Hospital acquired ("nosocomial") infections with bacteria which are multi-resistant to antibiotics are a growing medical problem. It is estimated that about 200,000 people die each year in the US and in Europe as a result of nosocomial infections. A substantial number of nosocomial blood stream infections are caused by infections with enterococci, of which some strains are especially feared because of their very high level of resistance against antibiotics. These strains are known as VRE (vancomycin resistant Enterococcus faecium).

Monoclonal antibodies binding to the surface of the bacteria enhance their destruction by immune cells (macrophages, neutrophils) and are thus potent antibacterial drugs. By using MAbstract^® and antibody libraries built from subsets of specialized B-cells, Crucell's scientists have generated monoclonal antibodies against targets which are highly conserved among all strains. The monoclonal antibodies will be developed as prophylactic drugs to be given to patients at high risk of developing these bacterial infections, for example, during certain surgical procedures or under intensive care.

Enterococci (two important species, E. faecium and E. faecalis) are bacteria that inhabit the human gut and are not normally pathogenic. However, they are highly resistant to most antibiotics and may translocate through the gut into the bloodstream under certain conditions. Enterococcus strains resistant to vancomycin (vancomycin resistant enterococci, VRE) have emerged as a major problem for patients in intensive care units and patients receiving transplants or suffering from hematologic malignancies. Mortality in these infections is as high as 35%.