The forgotten typers: The rise and fall of Weimar bacteriophage-typing (1921–1935)

Using bacteriophages to type (identify) bacteria was one of the most important tools of twentieth-century epidemiology. Challenging existing accounts’ focus on Anglophone research, this paper shows that modern phage-typing arose in German-speaking continental laboratories from 1921 onwards. Several factors contributed to this rise: the limitations of existing phenotypic systems; demobilized German bacteriologists’ interwar engagement with phages as a means to explore bacterial type variation; the existence of well-stocked and well-defined microbial culture collections with a strong focus on typhoid and paratyphoid; the standardization, free provision and calibration of phage diagnostic systems by a centralized laboratory network; and phage-typers’ implicit agreement to black-box ontological controversies about phages' nature in favour of a mission-oriented focus on practical epidemiological applications. The result was an experimental system that simultaneously treated phages as technical objects and epistemic things. Although the human network supporting phage-typing collapsed after the Nazi rise to power, Weimar-era phage researchers laid the foundation for modern phage-based diagnostics and epidemiology.