R.KAVITHA, M.PHARM, LECTURER, DEPARTMENT OF PHARMACEUTICS, SRM COLLEGE OF PHARMACY, SRM UNIVERSITY, KATTANKULATHUR. ` Small gram negative Intracellular bacteria ` Primary parasites found in the alimentary canal of arthropods-transmitted to humans by Lice/ flies /ticks and mites ` In humans – infect vascular endothelium and Reticuloendothelial cells ` Rickettsia named after HOWARD TAYLOR RICKETTS died of Typhus fever contracted during his studies ` Discovered spotted fever rickettsia (1906) HOWARD TAYLOR RICKETTS ` In smears from infected tissues,rickettsiae appear as pleomorphic gram negative coccobacilli ` Non motile non capsulated ` They stain bluish purple with Giemsa and Castaneda stains ` Unable to grow in cell free media ` Growth generally occurs in the cytoplasm of infected cells ` They are readily cultivated in the yolk sac of developing chick embryo ` They also grow on mouse fibroblast,HeLa,Hep2,Detroit-6 and other continuous cell lines but tissue cultures are not satisfactory for primary isolation ` Guinea pigs and mice are useful for the isolation of rickettsiae from patients ` Rickettsiae are readily inactivated by physical and chemical agents ` They are rapidly destroyed at 560 C and at RT when separated from host components. ` They can be preserved in skimmed milk or a suspending medium containing sucrose, potassium phosphate and glutamate(SPG medium) ` Family- Rickettsiae-three genera ◦ Rickettsia ◦ Orientia ◦ Ehrlichia ` Former members excluded ◦ Coxiella burnetti- Q fever Not athropod born ◦ Rochalimaea quintana Not an obligate intracellular parasite ` Genus recketsia ` Typhus fever group ` Epidemic typhus –R. prowazekii ` Endemic typhus – R.typhi ` Spotted fever group Tick borne ⁄mite borne ` R. ricketsii-rocky mountain spotted fever ` R. siberica-siberian tick typhus ` R. conori -indian tick typhus ` R. australis –Queensland tick typhus ` R. japonica- oriental spotted fever ` R. akari –Ricketsial pox ` Genus orientia ◦ Orientia tsutsugamushi – Scrub typhus ` Genus Ehrlichia ◦ E. sennetsu-Ehrlichiosis resembling glandular fever x E.chaffeenis – Human monocytic Ehrlichiosis ◦ E. equi- Human granulocytic Ehrlichiosis Genus Coxiella ` Coxiellla burnetti- Q fever Genus Bartonella ` B. bacilliformis – verruga peruvana ◦ Oroya fever /Carrion’s disease ` B. quintana – Trench fever (5 day fever ) x Rochalimaea quintana B.henselae- cat scratch disease Bacillary angiomatosis Bacillary peliosis..