R. prowazekii (Rickettsia prowazekii) is smaller in size than normal bacteria and is an obligately intracellular pathogen that use arthropod vector for the spread of epidemic Typhus fever. However, they are true bacteria, small coccobacilli that are normally stained with Giemsa and poorly by the Gram stain. Its cell wall morphology is that of a Gram-negative bacillus (Ref.1). Phylogenetically a member of the Alpha-subgroup of Proteobacteria, R. prowazekii along with R. typhi (Rickettsia typhi) is considered to be Typhus group Rickettsia. R. prowazekii evolved in close association with its arthropod vector, the human body louse, Pediculus humanus humanus. R. prowazekii do not spread effectively to other cells until their intracellular growth by binary fission results in accumulation of such large quantities [...]