This article deals with the institution of microbiology and its consequences to Brazilian public health during the last quarter of the XIXth century and the beginning of the XXth century. The author examines the work done by members of Escola Tropicalista Baiana and then by several constituents of another generation of physicians who, in Rio de Janeiro and São Paulo, researched yellow fever and other diseases from the perspective of the germ theory, trying to discover both its specific microbe as well as effective therapeutic and immunobiological treatments to those diseases. The article also examines the transition of the etiologic issue to the question of the means of transmission not only of yellow fever but also of malaria, correlating it with the coming of age both of Pasteurianism and Tropical Medicine. The adoption of Finlay's theory in Brazil and the successful campaigns led by Oswaldo Cruz in Rio de Janeiro, while the Brazilian capital was reshaped in accordance to a 'haussmannian' mould, initiates a new era in which Instituto Oswaldo Cruz and other medical institutions develop dynamic research programs in close syntony with European and North American Bacteriology and tropical medicine.
Bacteriology; Tropical Medicine; Yellow Fever; History of Public Health; Instituto Oswaldo Cruz