Identification and Characterization of Molecular Correlates of Disease in Invasive Streptococcus and Staphylococcus Infection Models

Abstract

Invasion into the host vasculature marks a dangerous, and often times fatal, complication of bacterial infections. One such severely invasive bacterium, Streptococcus pyogenes, is estimated to affect 18 million people globally, resulting in 517,000 deaths per year. In order to invade the host, S. pyogenes and others rely on an intricate and precisely-timed network of virulence factors and host response. To properly characterize this interplay, as well as the redundancies inherent in each, there is a need for technology which allows real-time characterization of bacterial factors and host immune response during invasive infections. In this dissertation, we will cover the use of two such technologies, namely molecular imaging and next-generation sequencing, towards the advancement of characterizing this essential interplay. Although typically considered as two separate disciplines, this dissertation will demonstrate the means by which these technologies work in tandem to produce new information as to the timing and composition of the infectious system. Within, we show that S. pyogenes is able to disseminate in host tissue without the use of streptokinase through the use of the genetically engineered light-producing pathogen Xen20. We also show that the luminescence production of this strain is dependent on both genetic regulation by the iol operon, and by catabolite repression of bacterial central metabolism. By exploiting this central metabolism-based indicator of cell physiology, we were able to design experiments which determine the mechanism of antibiosis of known compounds, indicating a potential for future high-throughput characterizations of lead targets. We also outline the automated construction and characterization of the Staphylococcus aureus Tager 104 genome, a potential “missing link” in the study of Staphylococcal pathogenesis.