Spirochetes Flashcards
Distinctive features
Lab diagnosis depends on
Spiral shaped Normal gram -ve rod Many plasmids Internal flagella Varied genome size
Anaerobic
Slow growing
fastidious
Some uncultivable
Antibody tests e.g gluttination or serological
Taxonomy
How are they recognised
How are they identified
3 main disease causing types - leptospira - borrelia - treponema Recognised by cell shape Identified by sequence analysis of 16s rRNA gene
Species identification by…
16s rRNA sequencing
16s rDNA gene is ell conserved and acts as molecular clock
Sequence it to speciate bacteria
Link between cell structure and motility
Deletion of flagella gene results in
Spiral shape due to internal flagella – AXIAL FILAMENTS
Cell shape defined by combination of peptidoglycan layer and bacterial cytoskeleton
Aflagellate non-motile strains which become straight rod shaped cells e.g treponema denticola
How do they swim
Counter rotation of internal flagella bundles results in rotation of cell body
Rotation = burrowing motility of spirochaetes e.g into tissue
Spirochaete cell surface
Cell wall
LPS
Cell wall components can modulate immune response –> MAJOR SHEATH PROTEINS
No LPS like other gram -ve bacteria
Spirochetes disease
Leptospira
Borrelia
Treponema
Weils disease, Leptospirosis
Lyme disease, relapsing fever
Syphilis, ANUG, periodontitis
Zoonotic infections
Lyme disease and Weil’s disease - animal involvement
Animal reservoir of infection which affects humans via vector
Lyme disease
Cause
Common where
Viewed by
What kind of microbe
Borrelia burgdoferi
Small spirochete only viewed by EM and Dark-field
Anaerobe
Zoonotic reservoir
Life cycle
Transmission via ticks
Arthropods in group arachnid
Ectoparasites of many vertebrate species
3 stages
Feed once in each
Bacteria live and multiply in midgut of ticks and are transmitted via saliva after biting humans
Stages of infection with BB - ACUTE
Can lead to
Bacteria hides in places like
Flu like symptoms often seen localised rash Erythema migrans Bulls-eye rash Other lessons at sites distal to innoculation
Arthritis
Cardiac symptoms
Palsy on face
Joints
Stages of infection of BB - chronic
Caused when
Seen 1 week-2 years post-infection
Neurological - meningitis, encephalitis, peripheral neuropath, CN palsies, vision impairment
Cardiac - myocarditis, blockages
Arthralgia and arthritis - months or years - often debilitating - due to reactivity to surface proteins - autoimmune
When bacteria enters sites other than bloodstream e.g neurons and joints
Borrelia burgdoferi
Mechanisms of infection
Motility
Invades epithelial cells
Invades many tissue types
No LPS but has lipoproteins called OSPA-D - harder to detect –> ANTIGENIC SHIFT
DbpA - mimics man protein
Copes with low iron levels by using manganese
Prevention and treatment
Vaccine
Preventive measures
Antibiotics eg doxycycline
Chronic infections harder to treat
Partially effective - target not expressed in humans
some side effects - may stimulate auto immune disease
Avoid endemic areas
Clothing, repellents
Relapsing fever
Caused by
Transmitted by
Mechanism
Can infect?
Borrelia recurrentis
Transmitted via ticks and human body louse
Febrile illness
Initial infection cleared but antigenic shift stimulates new set of symptoms
3-10 episodes
Can infect liver/spleen
