small, rod shaped bacteria

related to gram negative organisms

have diaminopimelic acid (DAP) in cell wall

obligate intracellular parasites

 can persist in the body for a long time

stains poorly with the gram stain better with Giemsa

caused by rickettsia rickettssii

most common rickettsial pathogen in US

distribution- Rocky Mountain region, Eastern and SE United States endemic in TN

wood tick (Dermacentor andersonii)

dog tick (Dermacentor variabilis)

by deer tick, Ixodes dammini

hard ticks from mice to humans

rickettsia multiply in the skin at site of tick bite

spread to blood and infect vascular endothelium in lung, spleen, brain, and skin

after week onset of fever, severe headache, myalgia and other respiratory symptoms

maculopapular rash appears a few days later often becoming petechial or purpuric

splenomegaly and neurolgical involvement is frequent with later onset of clotting defects

shock and death

individual camping, fishing, picnicking in wooded areas are highly susceptible

children playing in weeds or brush in Nashville area are highly susceptible

children are most commonly infected but their disease is milder

cytokine-mediated intracellular killing

clearance by cytotoxic CD8 lymphocytes

antibody response to outer membrane proteins may also be important

weil-felix test positive for proteus OX2 and OX19a

microimmunoflourescence methods and demonstration of a four fold or greater rise in antibody titer (1:160 or greater)

direct fluorescent antibody and PCR

tetracycline, doxycycline, flouroquinolones chloramphenicol, erythromycin

no vaccine

weakly staining, gram negative

stain well with Giemsa or Wright stain

can be easily seen by light microscopy in smears of patients with relapsing fever

from 7-20 periplasmic flagella

are microaerophilic and have complex nutritional needs

culture is generally unsuccessful

relapsing fever

lyme disease

recurrent episodes fever and septicemia seperated by afebrile periods

this results from antigenic variation

caused by as many as 15 species of borreliae

spread by infected soft ticks (Ornithodoros)

Ixodes scapularis in the eastern and midwestern US

Ixodes pacificus in the western US

worldwide distribution

adult ticks feed and mate on certain deer during late fall or winter and drop to the ground

eggs deposited on bushes hatch into larvae in the spring

in summer larvaue obtain blood meal from white-footed mouse (main reservoir)

larvae into nymphs 

during the following spring-summer, infected nymphs feed on vertebrate hosts including white footed mouse

infected or non infected nymphs fall off host and mature into adult males or females and then parasitize available deer to start cycle all over again

human host is usually infected by infected nymphs

erythema migrans begins as small papule and then enlarges over the next few weeks

headache, malaise, severe fatigue, fever, chills, myalgias, lymphadenopathy

stage 1-localized (1-4 weeks)

stage 2- disseminated (1-6 months)

stage 3- latent, persistent infection (1-30 years)

erythema migrans (bull's eye)

disseminated blood (fever, headache, fever, malaise)

localized: secondary annular lesions

disseminated: meningitis, carditis musculoskeletal pain, eye

localized: no manifestations acrodermatitis chronica atrophicans

disseminated: arthritic, chronic progressive neurologic/cardiac disorders

can be cultured in NSK medium from early stage cutaneous tissues but rarely seen at later stages

takes several weeks

primarly diagnosised based on clinical presentation and known exposure

small gram negative coccobacillus

intracellular obligate aeorobe (macrophages)

inhibits phagosome lysosome fusion

requires cysteine for growth; can grow on BCYE (buffered charcoal yeast extract)

facultative intracellular pathogen

LPS-appears to NOT be very toxic

lipid capsule- anti-phagocytic

factors taht inhibit phagosome-lysoome fusion and prevent acidification

Oklahoma, Missouri, and Arkansas,

but distributed throughout North America

bite from infected "hard-shell" tick (Ixodes, Dermacentor)

ingestion of contaminated meat or water, inhalation of infectious aerosol, skin abrasions, skinning of animals

A (most common)

B

ulceroglandular

oculoglandular

glandular

typhoidal

pneumonic

cutaneous ulcer/swollen lymph node

most common following skin abrasion or tick/fly bite (2-5 days)

ingestion or inhalation; baceteremic spread and seeding to lung, liver, spleen; fever, weight loss, pneumonia

mimics typhoid fever, brucellosis, tuberculosis

reactivity of bacteria with specific antiserum( agglutination of organism with antibodies against Francisella)

microagglutination detects antibody titer in serum

fluoresent Ab test can detect the organism in tissue specimen

natural infection confers long lasting and protective immunity

CMI plays a major role in resistance

vaccine is given to high risk individuals

streptomycin-high level of toxicity

gentamicin-alternative

fluroquinolones (ciprofloxacin)- good bactericidal activity in vitro and mouse animal models

large, aerobic, non motile gram positive rods that produce lecithinase

spore formers

polypeptide capsule composed of D-glutamic acid interfers with phagocytosis (plasmid-encoded)

protective antigen

EF

LF (lethal factor)

cutaneous (eshar)

pulmonary (woolsorter's disease)

ingestion

characterized by lesions (malignant pustule) on hands, forearms or head that may contain a dark bluish black fluid

erythematous papule develops 12-36 hours after entry of organism via breaks in skin which quickly progresses to the formation of a pustule and then a necrotic ulcer from which the infection may disseminate (eschar)

aquired by inhalation of spores by handlers of raw wool, hides or horse hair

spores germinate in the lungs or the tracheobronchial lymph nodes

symptoms include non-specific malaise, mild fever, and non productive cough

progressive respiratory distress and cyanosis will follow with massive edema of the neck and chest

infection of GI tract is common in animals but rare in humans

infection in humans results in abdominal pain, nausea, vomiting, and bloody diarrhea

gram stain, culture and immunofluorescent assays of fluid or pus from local lesions, blood and sputum

can be cultured on normal blood agar

serological tests can demonstrated the presence of agglutinating antibodies; antibodies to toxin antigen

historically susceptible to penicillin- resistance genes to penicillin and doxycycline have been transferred to the organism

now recommend ciprofloxacin

early treatment is important