Bacterial Infections of Blood and Vasculature Flashcards
1
Q
What is a vector?
A
-transmits between individuals in the reservoir
2
Q
What is a reservoirs?
A
-whatever life forms the pathogen is adapted to infect; the poor of hosts in which the pathogen is maintained
3
Q
B. burgdorferi Bacteriology
A
- motile spirochete
- flat-wave shape, not spiral
- stainable with giemsa, silver stain, IF, visible by standard microscopy
- tick-borne (I. scapularis in East, I. pacificus in West), most common one in US, much more common on East Coast
- highest risk in summer, when nymphs are feeding: many of them, smaller, people outside
- small mammal reservoirs (white footed mouse, wood rat) preferred by nymphs, large mammal hosts (deer) preferred by adults
- incidence in US is increasing due to expansion of deer herds; 20,000-30,000/yr; rate in Europe is similar
- almost always requires 24h attachment to transmit
4
Q
B. burgdorferi Pathogenesis
A
- disease begins w/ injection of B. Burgorferi into host by tick.
- asymptomatic clearance possible
- over the next 6 months, organism spreads. Erythema migrans rash (75%), antispirochete/autoantibodies raised. Very persistent skin infection established
- months to 1 yr after infection, immune and/or neurological issues arise. Lyme arthritis predisposed by HLA-DR4 and HLA-D2 genotypes and certain strains
- post lyme- 80% of untreated/undertreated report some neurological sequelae
- reinfections occur
5
Q
B Burgdorferi Exam Stage 1
A
- patient usually does not recall tick bite- get history of outdoor activity, not season and geographic location
- erythema migrans expanding rashes at or near bite site, bulls-eye appearance in a minority
- rash around tick = hypersensitivity, not Lyme
- Flu-like symptoms, fatigue, muscle aches, regional lymphadenopathy, low fever
- coinfection with erlichia or babesioa: high fever
6
Q
B Burgdorferi Exam Stage 2
A
- musculoskeletal and/or neurologic symptom
- intermittent arthritis, episodes about a week and recur, knee most common
- contracted in europe- blueish borrelial lymphocytoma on earlobe or nipple; also Acrodermatitis Chronica Atrophicans (ACA), a progressive fibrosing skin process on extremities
- lyme neuroborreliosis with cranial neuropathy, meningitis, or rarely encephalopathy- MRI or CT
- rarely cardiac involvement: arrhythmia or transient block
- rarely ophthalmic symptoms
7
Q
B Burgdorferi Exam Stage 3
A
- chronic lyme disease
- arthritis
- subacute encephalopathy
- chronic progressive encephalomyelitis
- late axonal neuropathies
- fibromyalgia
- patient may recall earlier episodes of Bell palsy, aseptic meningitis
8
Q
What are the labs for B. burgdorferi
A
- serology, ELISA, IFA can confirm exposure but not current infection, also takes 6-8 weeks
- patients who received the Lyme vaccine seropositive, seropositivity reamintains long term, seronegativity is reliable
- equivocal-positive titers can be confirmed by Western Blot
- biopsy of borrelial lymphocytoma or acrodermatitis might be useful
- organism may be cultured from tick
- Neuro symptoms= anti-Lyme IgM, IgG
- PCR testine
9
Q
What is the treatment for Lyme disease-
A
- treat patient who present with erythema migrans
- attempt empiric treatment of seropositive patients with symptoms unless pregnant
- early lyme improves rapidly with antibiotics
- amoxillin or doxycycline
- no evidence of benefit from longer antibiotic courses
- don’t add steroids for arthritis
- Jarisch-Herxheimer reaction
10
Q
What is the prevention of Lymes
A
- avoidance
- inspection
- prophylaxis in some areas
11
Q
What is the bacteriology of Louse-borne Relapsing Fever
A
- pathogen: B. recurrentis
- vector: Pediculus corporis- Louse
- reservoir: humans
- endemic to Africa, also seen in overcrowded homeless shelters
- transmission: louse crushing/ inoculation by scratching (scratch and crush transmission- attachment, feeding, defecating, scratching, inoculation)
12
Q
What is the bacteriology of tickborn bacteriology?
A
- pathogens: B hermsii, B turicatae, B parkeri, B duttonii, others
- vectors: soft-bodies ticks Ornithodoros spp
- reservoirs: many mammals and reptires
- transmission: bite of infected tick- usualy noctural, unnoticed
- endemic to Western US, southern British Columbia, Mexico, Central and South America, Asia, Africa, Mediterranean region
13
Q
What is the relapsing fever pathogenesis?
A
- spirochetes across vasculature, disseminate to spleen, bone marrow, liver, lungs, kidneys, CNS
- a strong IL10 response and neutralizing antibodies clear sepsis -> fever
- spriochetes vary their surface antigens in response to immune selection, when a new pool predominates, disease resumes
- fevered episodes repeat, lower fever and increasingly long breaks between as immune response improves
- louse borne- average of one relapse, mortality 4% treated, 40% un-
- tick borne- average 3 relapses, mortality <2% treated, 4-10% un-
- tickborne causes complications of pregnancy: abortion, premature birth, neonatal death
14
Q
How does relapsing fever show up on exam?
A
- two or more episodes of 3-5 days of high fever with low blood pressure, then a well week between
- also chills, arthralgias, nausea/vomiting, abdominal pain, mental status changes, nonproductive cough, diarrhea, dizziness, neck pain, photophobia, rash, and dysuria
- in louse-borne, also jaundice, petechiae, hemoptysis, epistaxis, and CNS involvement
15
Q
how does relapsing fever look on lab?
A
- perpheral blood smear: spirochetes visible by microscopy with Wright or Giemsa stain if blood taken during febrile period
- can also visualize bacteria with IF, darkfield, wet mounts, silver-stained biopsies
- CSF: mononuclear pleocytosis
- organism can be cultured from blood in special liquid medium, takes 2-6 weeks
- PCR assay available
- ELISA is available, better one in pipeline
16
Q
What is the relapsing fever treatment?
A
- tetracycline, doxycycline, erythromycin, penicillin G used in adults
- erythromucin in children and pregnant/nursing women
- IV penicillin or ceftriaxone for meningitis
- louse-borne takes one dose, tick-borne treat for 7-10 days
- Jarisch-Herxheimer reaction
