Rickettsia and bartonella Flashcards
Rickettsiae transmission
obligate intracellular bacteria. They have animal reservoirs and are transmitted to humans by arthropod vectors such as lice, mites and fleas.
rickettsia structure and visualization
gram-negative bacteria. Most frequently in pairs of rod-shaped cells with tapered ends, or as single coccobacilli. Stain poorly with bacteriologic stains, but they can be visualized readily in tissue with the Giemsa stain.
Rickettsia growth
obligate intracellular (grow in cytoplasm). • Rickettsiae have efficient transport systems for acquiring ATP, amino acids, and other metabolites from the host cell. They are capable of independent metabolism (TCA cycle and electron transport system), and use their own biosynthetic machinery to make proteins and other complex components. However, they cannot be cultivated on artificial medium
What cell does rickettsia infect
The bacteria invade the vascular endothelial cells and become widely disseminated throughout the vascular system. The pathology of rickettsial infections results from destruction of infected host cells.
Rickettsial diseases- clinical features
fever, headache, and rash. The rash is due to focal areas of infection that cause increased vascular permeability and edema. Thrombosis and blockage of the small blood vessels with extravasation of blood are late events in pathogenesis. Petechial lesions are a hallmark of rickettsial diseases. The clinical consequences of lesions in the brain, kidneys, lungs, and heart are much greater than those of the cutaneous lesions.
Compare the initial site of lesion in the three diseases cuased by Rickettsia and Orienta
Typhus group: rash appears first on the trunk and progresses to the extremities. Scrub Typhus group: rash is absent. Spotted fever group: rash appears first on the extremities, moves centripetally and involves the palms and soles
List the diseases in the Typhus group
epidemic typhus, Brills disease, and endemic typhus
Etiology/ transmission/ reservoirs of epidemic typhus
Rickettsia prowazekii. reservoirs in human and flying squirrels. • Transmission: Feces from human body louse and squirrel ecto-parasites. Prevalant during wars/ natural disasters
Epidemic Typhus clinical features
Erythematous macular rash starting 1-2 weeks after inoculation. The rash starts on the trunk and progresses to the extremities. Bacteremia, high fever, prostration, renal failure, stupor. Up to 70% mortality untreated
Epidemic Typhus prevention/ treatment
Live attenuated vaccine used in armed services and for people at risk. Insecticides to kill lice.
Treatment: Doxycycline.Live attenuated vaccine used in armed services and for people at risk. Insecticides to kill lice.
Treatment: Doxycycline.
etiology of Brill’s disease
Rickettsia prowazekii
Brills disease clinical features
• Similar to epidemic typhus except milder, usually no rash • Occurs many years after primary infection as a consequence of recrudescence, usually in immigrants from Eastern Europe who had typhus during World War II • If patients are infested with lice, there is a possibility of transmission • Brill’s disease can be the source of new outbreaks of epidemic typhus
Endemic typhus etiology, reservoir, transmission
Rickettsia typhi. Reservoirs are rats. Transmission from feces of rat fleas.
Endemic typhus clinical manifestations and treatment
Very similar to epidemic typhus but milder (>1% mortality rate). Treatment: Doxycycline or chloramphenicol
Etiology/ transmission/ reservoirs of scrub typhus
Etiology: Orientia tsutsugamushi. Common reservoirs: Chiggers (larval mites). The bacterium can be transmitted in mites from generation to generation by transovarian transmission. Transmission: Chigger bite
Scrub typhus clinical and treatment
Similar to epidemic typhus, except that rash is often absent and eschar develops at site of the chigger bite. Short-lived immunity because of antigenic variation. 7% mortality rate if untreated. Treatment: doxycycline or chloramphenicol
spotted fever etiology and transmission
Rickettsia rickettsii. Reservoir: widespread in wild mammals, birds, and ticks (transovarial passage).Transmission: tick bite. American dog tick in the East, Wood tick in the West, Lone Star tick in the South and Southeast
Spotted fever clinical
2-6 days after tick bite. Similar to typhus except that rash starts at extremities (wrists and ankles) and moves to trunk. Macular petechial rash. ≈7% mortality rate if untreated, but responds to tetracycline
Spotted fever prevention and treatment
No vaccine. Prompt tick removal. Treatment: Doxycycline (not in pregnant)
What kinds of cells do Ehrlichia and anaplasma species infect
their host target cells are phagocytic cells and they multiply within phagosomes
Clinical features of ehrlichiosis
fever, headache, and often, multisystem involvement. NO rash. leucopenia and thrombocytopenia
List diseases caused by ehrlichieae
Human Monocytotrophic Ehrlichiosis and Human Anaplasmosis
Etiology/ transmission/ reservoirs of human monocytotrophic ehrlichiosis
Ehrlichia chaffeensis, Ehrlichia ewingii. Common reservoir: deer. Transmission: bite from a hard tick (lone star tick, brown dog tick, american dog tick)
human monocytotrophic ehrlichiosi clinical
Incude fever, headache, chills, malaise, muscle pain, nausea, vomiting, diarrhea, confusion, conjunctival injection (red eyes), rash (60% of children, less than 30% of adults) erythroderma (sunburn-like rash) may occur in some patients. Some patients present with a rash very similar to RMSF. Thrombocytopenia, leukopenia or elevated LFTs
human monocytotrophic ehrlichiosis pathogenesis
Infect monocytes and macrophages. Can be fatal in immunocompromised individuals. Disease caused by E. ewingii is usually less severe
human monocytotrophic ehrlichiosis diagnosis
rapid: PCR from whole blood. During first week blood smear shows morulae (microcolonies of ehrlichiae) in the cytoplasm of white blood cells. Serology; immunofluorescence using antigen to detect antibodies. IgG is usually low/ negative in first week, and elevated by 2-4 weeks later.
human monocytotrophic ehrlichiosis treatment
Tetracycline or doxycycline
Human Anaplasmosis etiology, transmission, reservoir
Anaplasma phagocytophila. Common reservoir: deer. Transmission: bite from the same Ixodes tick as Lyme disease (soft tick)
Human Anaplasmosis pathogenesis
Infect circulating neutrophils
human anaplasmosis diagnosis and treatment
diagnosis: Inclusion bodies in neutrophils. Serology (IFA) (Note: some patients develop antibodies that cross-react in tests for Lyme disease). Treatment: doxycycline
name the bacteria body louse can carry
rickettsia (prowazekii) causes epidemic typhus, Bartonella quintana causes trench fever, Borrelia quintana causes bacillary angiomatosis peliosis.
Name flea assocated bacteria
Bartonlla henelae causes cat scratch fever. Rickettsia typhi causes endemic typhus
