Streptococcus pneumoniae: From molecular biology to host-pathogen interactions

Abstract

Streptococcus pneumoniae is the main cause of community acquired pneumonia and also produces meningitis,bacteremia, and otitis media, among others. Worldwide, these infections are the cause of substantial morbidityand mortality. Many different virulence factors have been described and most of them are surface-locatedmacromolecules, namely, the capsular polysaccharide and various pneumococcal proteins. Cell wallhydrolases (CWHs) specifically cleave covalent bonds of the peptidoglycan and associated polymers: mostCWHs are choline-binding proteins (CBPs) and are among the most well-known surface proteinsP. neumococcal CBPs have been investigated due to their role in pathogenesis and as candidate antigens forimproved vaccines. Among the complex host-parasite interactions characteristic of pneumococcal disease,nasopharyngeal colonization is the first step. CBPs appear to play a central role in the development of thecarrier state, possibly by affecting biofilm formation and development. Although the role of biofilms in thepathogenesis of some chronic human infections is currently widely accepted, the molecular bases underlyingthe formation of pneumococcal biofilms are only recently being studied. Among therapeutic strategies tocombat multidrug-resistant pneumococcal infections, the use of purified phage or bacteria-encoded CWHsboth in vitro and in animal models is under investigation.