noun rick·ett·sia \ri-ˈket-sē-ə\
plural rick·ett·si·as or rick·ett·si·ae\-sē-ˌē, -ˌī\ also rick·ett·sia

Definition of RICKETTSIA

:  any of a family (Rickettsiaceae) of rod-shaped, coccoid, or diplococcus-shaped, often pleomorphic gram-negative bacteria that are intracellular parasites of arthropods (as lice or ticks) and when transmitted to humans cause various diseases (as typhus)
rick·ett·si·al \-sē-əl\ adjective


New Latin, genus name, from Howard T. Ricketts †1910 American pathologist
First Known Use: 1919
Medical Dictionary


noun rick·ett·sia \ri-ˈket-sē-ə\

Medical Definition of RICKETTSIA

capitalized :  the type genus of the family Rickettsiaceae comprising rod-shaped, coccoid, or diplococcus-shaped often pleomorphic bacteria that live intracellularly in biting arthropods (as lice or ticks) and when transmitted to humans by the bite of an arthropod host cause a number of serious diseases (as Rocky Mountain spotted fever and typhus)
plural rick·ett·si·ae \-ˌē\ also rick·ett·sias or rick·ett·sia :  any bacterium of the order Rickettsiales and especially of the family Rickettsiaceae


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