Rickettsiaceae Flashcards
Small (0.5 – 2 um) non-motile, pleomorphic bacilli, have a g(-) cell wall
RICKETTSIACEAE
It is the simplest
bacterial form and
considered transitional
organism between
bacteria and viruses
RICKETTSIACEAE
This group of organisms
infect wild animals, with
humans acting as
accidental hosts
RICKETTSIACEAE
all species require living cells for growth except for
Bartonella quintana
small organism, pleomorphic, gram-negative bacilli and multiplies by binary fission in the
cytoplasm of host cells (the release of mature rickettsiae results in the lysis of the host cell)
Rickettsia
survives only briefly outside of a host and multiply only intracellularly in the cytosol of the host
cell
Rickettsia
Rickettsia :
Lysis of cell wall
Rickettsia prowazekii
Rickettsia:
Filopodium focal lysis
Ricketssia rickettsii
Rickettsia:
Budding
Rickettsia tsutsugamushi
contributes to its intracellular activity.
Phospholipase A2
can be passed from generation to generation of ticks through their eggs (transovarian
passage)
Rickettsia ricketsii
Ricketssia Groups of Bacteria
Spotted fever group
Typhus Group
Scrub typhus group
They grow in the cytoplasm of host cell and released via ―pinching‖ off‖ a host cell membranebound rickettsia
Orientia tsutsugamushi
- It was placed into a separate genus due to the absence of LPS and peptidoglycan, and the
presence of 54 – 58 kDa major surface proteins
It is transovarially maintained in mites (Leptotrombidium
Orientia tsutsugamushi
Humans and rats are accidental, nonessential dead-end hosts
Orientia tsutsugamushi
Small (0.5 um, gram negative coccobacilli and undergo intracellular development cycle following
infection of circulating WBC
Ehrlichia
nfection of circulating WBC
- They undergo 3 developmental stages similar to Chlamydiae: EB, initial bodies and morulae
Ehrlichia
3 Developmental stages of Erlichia
Elementary body, Initial body, Morulae
Wright-Giemsa staining of intravacuolar microcolony resembles?
“mulberry” morula
Infects monocytes and causes HME (Human Monocytic Ehrlichiosis)
Erlichia Chaffeensis
It is transmitted to humans by the lone star tick (Amblyomma americanum)
Erlichia Chaffeensis
Can also be transmitted by D. andersoni and Ixodes pacificus
Erlichia Chaffeensis
Causes HGE (Human Granulocytotropic Ehrlichiosis)
Erlichia phagocytophila
Transmitted by I. pacificus, I. scapularis, and I. ricinus ticks, and white footed mouse
(Peromyscus leucopus)
Erlichia phagocytophila
This is the causative agent of Q fever – a systemic infection that affects the lungs
Coxiella burnetti
- Strictly intrancellular, gram-negative bacteria, smaller that Rickettsia species; more resistant to
chemical and physical agents, dessication and sunlight (able to withstand harsh environmental
conditions)
Coxiella burnetti
Can survive extracellularly because of its endospore-like body – can be grown only in lung cells
Coxiella burnetti
In infected animals, organisms are shed in urine, feces, milk and birth products
- Humans are infected by the inhalation of contaminated aerosols from dried animal feces
Coxiella burnetti
In contrast to rickettsial infection, a rash does not develop following infection
Coxiella burnetti
In contrast to rickettsial infection, a rash does not develop following infection
- It does not multiply in bacteriologic culture media
Coxiella burnetti
Shell vial assay with human lung fibroblasts is used to isolate the organism from the buffy coat
and biopsy specimens has not resulted in any laboratory acquired infections
Coxiella burnetti
serologic techniques for detection of Coxiella burnetti
IFA, CF, EIA
Animal reservoir – cattle, sheep and goats
Coxiella burnetti
Facultative intracellular gram-negative bacilli
- Do not synthesize acid from carbohydrates
Bartonella
They live within red blood cells in their natural mammalian hosts
Bartonella
They can be cultivated in blood enriched with 5% CO2 (CAP) or charcoal yeast extract agar
(CYEA)
Bartonella
Trench fever is transmitted from person to louse (Pediculus humanus corporis) to another
person.
Bartonella
Bartonella species: negative catalase, oxidase and urease
Bartonella henselae
Bartonella that is an etiologic agent of trench fever
Bartonella quintana
Bartonella that is an etiologic agent og infective endocarditis
Bartonella elizabethae
Bartonella that is an etiologic agent of Oraya fever (chronic verruga peruana) and febrile acute hemolytic anemia
Bartonella bacilliformis
for the detection of morulae during the febrile stage of Ehrlichiosis
Giemsa or Diff-Quik stains
agglutination of certain strains of Proteus vulgaris by serum from patients
with rickettsial diseases; presumptive test
Weil-Felix reaction
– excellent sensitivity for detecting antibodies to rickettsia;
early diagnosis of RMSF within 7 – 10 days after onset of symptoms
Microimmunofluorescent Dot test
– do not induce Weil-Felix antibody in infected patients
- Antibodies to rickettsia (except R. rickettsia) cannot be reliably detected until at least 2 weeks
after the patient has become ill
- Q fever, Ehrlichiosis and Rickettsial pox
