An outbreak of variably vancomycin dependent enterococcus

Vancomycin Resistant Enterococcus (VRE) can contribute significantly to the morbidity of immunocompromised patients. Vancomycin Dependent Enterococcus (VDE) has been rarely reported. We report a nosocomial cluster of Variably Vancomycin Dependent Enterococcus faecium (VVDE) in bone marrow transplant (BMT) patients. Between 6796 and 2/97 all routine surveillance bacterial cultures were negative for VRE. On 2/3/97, the first BMT patient developed VRE bacteremia. Over the next two weeks, five more BMT patients had stool cultures newly positive for VRE. One patient was identified in the fourth week. All patients were on the same medical floor. The seven isolates were evaluated by Pulse Field Gel Electrophoresis (PFGE); five were identical. Three of these five showed weak colony growth on sheep blood agar, with strong growth in plates containing 10ug and 64 ug of vancomycin.The first and fifth identical isolates were VRE but did not need the presence of vancomycin for normal colony growth. Van B phenotype was found by Polymerase Chain Reaction. Per oncology protocol, all of the patients had been treated empirically with vncomycin from two days before BMT until neutropenia had resolved. They had been exposed to vancomycin from 5-48 days before the development of VRE/VVDE. Aggressive infection control measures were successful in controlling nosocomial spread. Vancomycin use policy was revised to limit empiric use in BMT patients. No further isolation of this enterococcus was identified. Different isolates of this identical strain of enterococcus illustrated both resistance to vancomycin as well as dependence upon it for normal growth. The formation of vancomycin dependent ligases through antibiotic pressure has been the proposed mechanism for this development. The presence of VVDE complicating the dramatic increase in hospital VRE argues for increased infection control practices and careful empiric antibiotic use in compromised patients.