Dr. Ehrlich and his lab are interested in how chronic bacterial pathogens persist in the face of antimicrobial therapy, and the innate and adaptive host responses. To understand this complex phenomenon, Dr. Ehrlich promulgated the rubric of “bacterial plurality,” which embodies the concept that chronic pathogens display enormous heterogeneity at many levels including: phenotypic, metabolic and genotypic. The reasoning behind the development of this theoretical construct was to provide a paradigm that more accurately models chronic pathogenic processes enabling the development of rational therapies for these diseases that are recalcitrant to current medical management