1. Overview of some general cell wall characteristics of VSSA and VISA strains showing the key regulatory elements linked to intermediate-level vancomycin resistance, as uncovered by comparative genomics and genetic studies.
Overview of some general cell wall characteristics of VSSA and VISA strains showing the key regulatory elements linked to intermediate-level vancomycin resistance, as uncovered by comparative genomics and genetic studies. (A) VSSA strain in the absence of vancomycin showing a normal peptidoglycan (PG) layer, with the production of protein A and normal capsular polysaccharide expression. Also shown is the division septum, where cell wall growth occurs. The lipid II-linked PG precursors assemble at the division septa, and the dipeptide moiety of lipid II is the lethal target of vancomycin. (B) VISA strain with mutations in either the graRS, vraSR, or walKR operon (or all) that might lead to their respective regulons remaining in an activated “locked-on” or otherwise modified state. The consequence of this modification includes cell wall thickening, decreased autolysis, reduced protein A production, increased capsule expression, increased d-alanylation of teichoic acids, and reduced agr activity.
Benjamin P. Howden et al. Clin. Microbiol. Rev. 2010; doi: /CMR