Comparative Proteomics of Streptococcus pneumoniae Response to Vancomycin Treatment

Streptococcus pneumoniae is a gram-positive pathogen that causes otitis media, pneumonia, meningitis, and other serious diseases. Vancomycin is one of the most important drugs currently used for the treatment of gram-positive bacterial infections, representing, importantly, the last line of defense against bacteria that have developed resistance to other antibiotics. While primary efforts of most investigations focused on the antibacterial mechanism of vancomycin, few studies have been performed to assess the tolerance mechanism of bacteria to vancomycin. In this work, whole cellular proteins were extracted from S. pneumoniae D39 with or without vancomycin treatment. Subsequently, differentially expressed proteins (DEPs) were identified with two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry (MS)/MS. In total, 27 proteins were upregulated and four proteins were downregulated in vancomycin-treated S. pneumoniae. Gene ontology analysis indicated that these DEPs were mainly involved in the nucleic acid, protein, and carbohydrate biosynthetic processes. Verification experiments with real-time quantitative polymerase chain reaction showed that the gene expression profiles were consistent with proteomic data. These new observations may serve as a valuable resource for future investigations of vancomycin tolerance mechanisms of S. pneumoniae.