Unit 4 - The Order Rickettsiales Flashcards
What is the morphology of organisms in the order Rickettsiales?
rod shaped, coccoid, and often pleomorphic
Are organisms in the order Rickettsiales gram negative or positive?
gram negative - but stain poorly
What stains help visualize organisms in the order Rickettsiales?
Giemsa, Macchiavello, and Gimenez stains
What type of organisms are Rickettsiales?
obligate intracellular parasites
How do Rickettsiae enter the host cell?
by parasite-induced phagocytosis
How do Rickettsiae escape digestion?
in the phagolysosome by either escaping into the cytoplasm or remaining in the phagocytic vacuole and resisting digestion
How do rickettsiae multiply?
by binary fission
How are rickettsiae released?
by cell lysis or exocytosis
What organisms in the family Rickettsiaceae associated with?
nucleated host cells
What genera are included in the tribe Rickettsieae?
those that are pathogenic primarily for humans
When released from cells, what can the bacteria in the tribe Rickettsieae do?
infect vertebrate hosts when the vectors obtain a blood meal
What are the three distinct biotypes of the genus Rickettsia?
Typhus group (A), Scrub Typhus group (B), and Spotted fever group ©
What are two species belong in the typhus group?
Rickettsia prowazekii and Rickettsia typhi
What does Rickettsia prowazekii the cause of?
epidemic typhus - a louse-borne disease seen in conditions of war, poverty, and famine
How does clinical disease from Rickettsia prowazekii progress?
headache, fever, skin rash, and if untreated death
Is there an animal intermediate host for Rickettsia prowazekii?
no
What does Rickettsia typhi cause?
mouse typhus
How do humans get mouse typhus?
by accidental exposure to the rat flea or louse
What species belongs in the scrub typhus group?
Rickettsia tsutsugamushi
What does Rickettsia tsutsugamushi cause?
srub typhus or chigger-borne typhus
What are the vectors for Rickettsia tsutsugamushi?
mite larvae or chiggers
What species belings in the spotted fever group?
Rickettsia rickettsii
What does Rickettsia rickettsii cause?
Rocky-Mountain spotted fever
What transmits Rickettsia rickettsii?
ticks