Immunogenic proteins in the cell envelope and cytoplasm of vancomycin-resistant enterococci

Because of the continuous advent of new modes of antimicrobial resistance, it has become difficult to control vancomycin-resistant enterococci (VRE) with standard antibiotics. Therefore, in the interest of public health, early diagnostic methods and a greater knowledge of the pathogenic process are urgently needed to prevent the spread of VRE in humans and animals. To this end, we sought immunogenic proteins suitable for the serological diagnosis of VanA-, VanB-, VanC1-, and VanC2-type VRE. Proteins were extracted from cell envelope (CE) and cytoplasm (CP), and anti-VRE guinea pig serum was used to identify immunogenic proteins. Two immunogenic proteins of 129 and 29 kDa were identified in the CE and CP of VanA, respectively, while a 28-kDa protein was identified in the CP of VanB. Additionally, the CE of VanC1 contained two immunogenic proteins of 30 and 46 kDa, while the CP of VanC1 contained two proteins of 19 and 30 kDa. The CE of VanC2 possessed one immunogenic protein of 40 kDa. These proteins, which were specific to individual subtypes of VRE, will likely prove useful in the serological diagnosis of enterococcal infections and in the study of enterococcal pathogenesis.