The Presence of Peptidoglycan O -Acetyltransferase in Various Staphylococcal Species Correlates with Lysozyme Resistance and Pathogenicity

Abstract

Human-pathogenic bacteria that are able to cause persistent infections must have developed mechanisms to resist the immune defense system. Lysozyme, a cell wall-lytic enzyme, is one of the first defense compounds induced in serum and tissues after the onset of infection. Recently, we showed that Staphylococcus aureus is resistant to lysozyme by O acetylating its peptidoglycan (PG) by O -acetyltransferase (OatA). We asked the question of which staphylococcal species PG is O acetylated. We applied various methods, such as genome analysis, PCR, Southern blotting, lysozyme sensitivity assay, and verification of O acetylation of PG by high-performance liquid chromatography (HPLC) analysis. PCR analysis using S. aureus -derived oatA primers and Southern blotting did not yield reliable results with other staphylococcal species. Therefore, we used the HPLC-based assay to directly detect PG O acetylation. Our studies revealed that the muramic acid was O acetylated only in pathogenic, lysozyme-resistant staphylococci (e.g., S. aureus , S. epidermidis , S. lugdunensis , and others). All nonpathogenic species were lysozyme sensitive. They can be divided into sensitive species (e.g., S. carnosus , S. gallinarum , and S. xylosus ) and hypersensitive species (e.g., S. equorum , S. lentus , and S. arlettae ). In all lysozyme-sensitive species, the analyzed PG was de-O-acetylated. When we transformed the oatA gene from lysozyme-resistant S. aureus into S. carnosus , the corresponding transformants also became lysozyme resistant.