Paper BI-TuP3
Time of Flight Secondary Ion Mass Spectrometry Characterization of the Surface Polysaccharides of Group B Streptococcus

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

Group B Streptococcus (GBS) is a leading cause of sepsis and meningitis in neonates and immunocompromised adults in western countries. The surface of GBS is well characterized by standard microbiological techniques and therefore makes a good test system for analyzing bacteria using Time of Flight Secondary Ion Mass Spectrometry. GBS is layered with a capsule composed of five distinct polysaccharides containing glucose, galactose, N-acetylneuraminic acid, rhamnose, and N-acetylglucosamine. The capsule makes up 10 to 30% of the dry weight of the microorganism and is only present on the surface. In this work, the five monosaccharides, pure capsule from type III GBS, and UV killed GBS strain COH1 and acapsular GBS strain COH1-13 were investigated. It was observed that the pure monosaccharide fragmentation patterns followed C_xH_2xO_x⁺, and that the largest fragment observed of the monosaccharides was with the loss of H₂O, OH^- or H₃O⁺. The presence of sodium, magnesium, and calcium in the purified samples made direct comparison with the pure monosaccharides difficult due to cationization effects. Spectra from clusters of GBS and single organisms were acquired using the high mass resolution imaging mode and constructing a spectrum from a region of interest. The biggest differences between COH1 and COH13 were seen in the high mass region of the spectra.