Loeffler succeeded in cultivating C. diphtheriae, the diphtheria bacillus. He reproduced the characteristic membrane by swabbing the mucous membranes of various animals with pure cultures of the bacillus.
In this paper Loeffler, who was working as one of Koch's assistants, stated on p. 424 three postulates similar to Koch's 4 postulates:
1. The organisms must be shown to be constantly present in characteristic form and arrangement in the diseased tissue.
2. The organisms which, from their behavior appear to be responsible for the disease, must be isolated and cultivated in purity.
3. The pure cultures must be shown to induce disease experimentally.

D. Jay Grimes, "Koch's postulates- then and now," Microbe 1 (2006) 223-228.

Discovery of Burkholderia mallei, causative organism of glanders. Preliminary notice in Dtsch. med. Wschr., 1882, 8, 707.

Loeffler, Professor of Hygiene at Greifswald, made many discoveries in bacteriology. His history of the subject was the first and only history of bacteriology prior to the publication of Bulloch's History of bacteriology (1938). It was unfortunately left unfinished. Digital facsimile from Biodiversity Heritage Library at this link.

Isolation of Salm. typhi-murium.

Loeffler and Frosch proved that foot-and-mouth disease is caused by a filter-passing virus; this was the first recognition that a virus causes disease.