The strain was isolated in 1938 from a patient in Sumatra, Indonesia, by Wolff (1953), who quotes in under the serovar name hardjo. The serovar is first mentioned in the list of Wolff and Broom of 1954.
The strain was submitted to factor analysis by Kmety (1977), who, on the basis of the results, placed it in the subgroup Wolffi.
By DNA restriction endonuclease analysis difference among strains of this serovar were reported (Thiermann and Ellis, 1986). They suggest deviding the serovar into two different genotypes hardjoprajitno and hardjobovis.