Download - Rickettsia and Orientia
RickettsiaRickettsia and and OrientiaOrientia
• RickettsiaRickettsia ( (RickettsiaRickettsia and and OrientiaOrientia))•EhrlichiaEhrlichia ( (EhrlichiaEhrlichia and and AnaplasmaAnaplasma))•small (0.3 × 1 to 2 μm) small (0.3 × 1 to 2 μm) •stained poorly with the Gram stain stained poorly with the Gram stain •grew only in the cytoplasm ofgrew only in the cytoplasm of
eukaryotic cells eukaryotic cells
RickettsiaRickettsia and and OrientiaOrientia
• structurally similar to gram-negative rods
• contain DNA, ribonucleic acid (RNA), and enzymes and ribosomes
• multiply by binary fission• inhibited by antibiotics
RickettsiaRickettsia and and OrientiaOrientia
• maintained in animal and arthropod reservoirs
• transmitted by arthropod vectors (e.g., ticks, mites, lice, fleas)
• humans are accidental hosts• spotted fever group and the typhus
group
RickettsiaRickettsia and and OrientiaOrientia
• Organism Human Disease Distribution Spotted Fever Group R. Rickettsii Rocky Mountain spo.f. Western hem R. Africae African tick bite f. Eastern-Sou Africa R. Akari RickettsialpoxWorldwid R. Australis Australian tick typhus Australia
R. Conorii Mediterranean spo. f. Mediterranean R.japonica Japanese spotted f. Japan R. Sibirica Siberian tick typhus Siberia, Mongolia, Typhus group R. Prowazekii Epidemic Worldwide R.typhi EndemicWorldwide Scrub typhus group O.tsutsugamishi Scrub typhus Asia, Ocenia
RickettsiaRickettsia and and OrientiaOrientia
Bite of brown dog tick-Bite of brown dog tick-Rhipicephalus sanguineusRhipicephalus sanguineus
RickettsiaRickettsia and and OrientiaOrientia
• peptidoglycan layer is minimal
• LPS has only weak endotoxin activity
• binary fission is slow
RickettsiaRickettsia and and OrientiaOrientia• No toxins• No host immune response• R. rickettsii is most common rickettsial
pathogen in United States • Hard ticks are the primary reservoirs and
vectors (Dermacentor)• Transmission requires prolonged contact
(24 to 48 hours) • Distribution in Western hemisphere• Disease is most common April through
October
RickettsiaRickettsia and and OrientiaOrientia
• 2-14 days• Painless tick bite• High fever, headache, fever, chills• Rash macular to petechial• First extremities and then trunk• GIS symptoms, respiratory failure• Encephalitis, renal failure
RickettsiaRickettsia and and OrientiaOrientia
• Tissue culture and embrynonated eggs
• Microscopy• Serology• PCR
RickettsiaRickettsia and and OrientiaOrientia
• Tetracycline• Fluroquinolones
RickettsiaRickettsia and and OrientiaOrientia
• Epidemic typhus• Louse-borne typhus• Humans are the primary reservoir• Replicates in endothelial cells with
resulting vasculitis
RickettsiaRickettsia and and OrientiaOrientia• Humans are the primary reservoir, with person-
to-person transmission by louse vector • It is believed that sporadic disease is spread from
squirrels to humans via squirrel fleas • Recrudescent disease can develop years after
initial infection • People at greatest risk are those living in
crowded, unsanitary conditions • Disease is worldwide, with most infections in
Central and South America and Africa • Sporadic disease is seen in the eastern United
States
RickettsiaRickettsia and and OrientiaOrientia
• 2- to 30-day incubation period • nonspecific symptoms • less than 40% of the patients had a
petechial or macular rash • myocarditis and central nervous
system dysfunction • Brill-Zinsser disease-milder
RickettsiaRickettsia and and OrientiaOrientia
• MIF test is the diagnostic method of choice
• Tetracyclines and chloramphenicol • Formaldehyde-inactivated typhus
vaccine
Rickettsia typhiRickettsia typhi• Endemic or murine typhus • worldwide • Rodents are the primary reservoir, • Rat flea (Xenopsylla cheopis) is the
principal vector • 7 to 14 days • A rash develops • Typically restricted to the chest and
abdomen • Indirect fluorescent assay
Orientia tsutsugamushiOrientia tsutsugamushi • Scrub typhus• Mites• Asia, Oceania• 6-18 days• Sudden onset• Maculo-papular rash• LAP, SM• Tetracycline, chloramphenicol
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella
• Anaplasmataceae: Anaplasma, Ehrlichia, Neorickettsia, and Wolbachia
• survival within a cytoplasmic vacuole in the infected arthropod or mammalian cell
• infection of hematopoietic cells
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella
Multiple morulae of Ehrlichia canis in DH82 tissue culture cells
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella
• Small, intracellular bacteria • Stain poorly with Gram stainReplicates in
phagosome of infected cells • Intracellular growth protects bacteria from
immune clearance • Able to prevent fusion of phagosome with
lysosome of monocytes or granulocytes • Initiates inflammatory response that
contributes to pathology
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella• Depending on the species of Ehrlichia, important
reservoirs are white-tailed deer, white-footed mouse, etc
• Ticks are important vectors, but transovarian transmission in inefficient
• Disease in United States is most common in the Atlantic states; northern, central, and southern Midwest states; and northern California
• People at greatest risk are those exposed to ticks in the endemic areas
• Disease is most common from April to October
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella• Human monocytic ehrlichiosis is caused by E.
chaffeensis • 1 to 3 weeks after a tick bite, patients develop a
flulike illness with fever, headache, and myalgias • Gastrointestinal symptoms develop in fewer than
half the infected patients • late-onset rash develops in 30% to 40% of
patients • Leukopenia, thrombocytopenia, and elevated
serum transaminases
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella
• Canine Granulocytic Ehrlichiosis E. ewingii • Human anaplasmosis, A. phagocytophilum • More than half the infected patients require
hospitalization, and severe complications are common
• Mortality is rare
Ehrlichia, AnaplasmaEhrlichia, Anaplasma, and , and CoxiellaCoxiella• Giemsa-stained preparations of peripheral blood
should be performed, morulae diagnostic • PCR• Tetracycline, rifampin pregnant women• Vaccines are not available
Coxiella burnetiiCoxiella burnetii• more closely related to Legionella and
Francisella • Q fever, which may be asymptomatic in
humans and develops either acutely or as a chronic infection
• small, pleomorphic coccobacillus (0.2 to 0.7 μm)
• The small replicating cells will mature to large-cell variants, which then evolve to stable spores
Coxiella burnetiiCoxiella burnetii
• inhalation of airborne particles • more by the environment• Coxiella proliferate in the respiratory
tract and then disseminate to other organs
• pneumonia and granulomatous hepatitis
• most chronic infections manifest as endocarditis
Coxiella burnetiiCoxiella burnetii• antigenic variation • C. burnetii is extremely stable in harsh
environmental conditions • Many reservoirs, including mammals, birds, and
ticks • Most human infections associated with contact
with infected cattle, sheep, goats, dogs, and cats • Most disease acquired through inhalation;
possible disease from consumption of contaminated milk; ticks are not an important vector for human disease
• Worldwide distribution• No seasonal incidence
Coxiella burnetiiCoxiella burnetii
• Acute diseases include influenza-like syndrome, atypical pneumonia, hepatitis, pericarditis, myocarditis, meningoencephalitis
• Chronic diseases include endocarditis, hepatitis, pulmonary disease, and infection of pregnant women
Coxiella burnetiiCoxiella burnetii• most common presentation of chronic Q fever
is subacute endocarditis • culture (not commonly performed),
polymerase chain reaction (PCR), or by specific serologic tests
• serology is the most commonly used diagnostic test
• Tetracycline• combination of drugs, such as rifampin
and either doxycycline or trimethoprim-sulfamethoxazole