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. It is our belief that the extant paradigms of bacterial pathogenesis passed down to us from Robert Koch and developed for acute epidemic infections, although powerful and useful for clonal planktonic infections, acted for decades as blinders toward our understanding of chronic infections.