(221i) Dynamic Interactions of Live Group B Streptococci with Soluble and Adsorbed Fibronectin

Group B Streptococci (GBS) are a leading cause of sepsis and meningitis in newborns, and an emerging cause of serious bacterial infections in immunocompromised adults and the elderly. The streptococcal C5a peptidase (ScpB) of GBS is a surface associated endopeptidase that is found in virtually all clinical isolates of GBS. ScpB inhibits neutrophil chemotaxis by enzymatically cleaving the complement component C5a. ScpB is also a known Fibronectin (Fn) adhesin; however, it only binds to immobilized Fn and not soluble Fn. This research focuses on using the Atomic Force Microscope (AFM) to probe live GBS with Fn in two different conformational states. First, GBS is probed with Fn chemisorbed directly to a gold coated AFM cantilever, and second, Fn is tethered is to the probe via the bifunctional cross linker pyridyldithio poly(ethylene glycol) succinimidylpropionate, then back filled with a shorter PEG silane. This immobilization strategy is designed to present FN on the probe in a soluble form. Control experiments with Bovine Serum Albumin showed that the adhesion was specific for Fn, and it was found that adhesion forces were higher with Fn adsorbed onto gold than with the soluble presentation of Fn.