Microbiology-Spirochetes Flashcards Preview

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Flashcards in Microbiology-Spirochetes Deck (21)

Organisms that exhibit corkscrew motility, don’t gram stain and grow slowly in vitro or not at all

Spirochetes. Note that treponema cannot be grown in culture, but borrelia and leptospira can.


Pathogenic spirochete genuses

1) Treponema (pallidum and carateum) 2) Borrelia 3) Leptospira


Pathogen that causes Lyme disease

Borrelia burgdorferia


Most common arthropod-borne infection in the US? What is the vector?

Lyme disease: hard deer trick, most often transmitted by the tick in the nymph phase.


Why do many people not realize they are being bitten by a deer tick that transmits borrelia burgdorferia?

Infection is most commonly transmitted by the nymphs, which are very hard to see.


Life cycle of deer ticks

1) Larvae infect birds and rodents in the summer after hatching from eggs in the spring. 2) Over fall and winter the larvae become nymphs which can infect humans, deer, foxes in the spring and summer. 3) Nymph becomes an adult. Note that this is a 2 year cycle and deers are asymptomatic.


Stages of lyme disease. When do antibiotics work?

Stage 1) Tick initiates feeding, at ~3 days bacteria activated, disseminated in tick, injected into dermis and cause localized infection Stage 2) Dissemination to heart, CNS, skin, joint and Bell’s palsy. Antibiotics work to clear the organism at these stages 3) Persistent infection with arthritis, meningoencephalitis and neuropathies.


Skin manifestations of Lyme disease

Stage I: erythema migrants. Stage II: secondary annular skin lesions.


Diagnosis of lyme disease

CLINICAL: erythema migrants, or at least 1 late manifestation (MSK, CNS, CV) + lab confirmation. LAB: isolation of B. burgdorferi, IgM/IgG against spirochetes. Note that you shouldn’t look for antibodies if someone has erythema migrans because it is too early in infection for antibody formation.


Antibody tests for Lyme disease 

1) ELISA, if positive 2) Western Blot. It works well in patients with stage 2-3 lyme disease


Treatment of lyme disease?

Oral doxycycline. If arthritis or CNS give IV.


Regions endemic with Lyme disease

Northeast and great lakes area


Best way to remove a tick

Grasp it with tweezers and pull


Disease that looks like lyme disease, found in Missouri and caused by the lone star tick (Amblyomma americanum)? How do you treat it?

Southern Tick-associated rash illness….also treated with antibiotics.


A patient with Lyme disease presents with relapsing fever. What is the mechanism of this relapsing fever? What other conditions are associated with relapsing fever?

The surface of the borrelia continually changes it surface and continually induces immune response. There are also epidemic (louse-borne) forms and endemic (soft-shelled tick-borne) forms.


A patient presents with relapsing fever, jaundice and CNS involvement during war time. What is the most likely organism causing this and where does it come from?

Borrelia recurrentis from louse. The reservoir is humans.


A patient presents with endemic relapsing fever, jaundice and CNS involvement. What is the most likely organism and where does it come from?

Borrelia hermsii. The reservoir can be ticks and animals.


Definitive way to diagnose relapsing fever caused by borrelia?

Spirochetes on peripheral blood smear.


Primary route of transmission of leptospira interrogans

Animal urine into water, we ingest the water


A patient presents with acute fever, reddening of the eyes, jaundice, renal failure and meningitis. Symptoms began shortly after swimming in a lake. What spirochete is most likely causing his condition?

This is Weil’s disease caused by leptospira interrogans


Leptospirosis prophylaxis