spirochetes Flashcards
spirochetes characteristics
- corkscrew shaped
- motile
- gram –
- very thin (viewed by dark field microscopy or EM)
- varied genome size
- many plasmids (large)
- unique method of motility via internal flagella
- anaerobic, fastidious, slow growing
- many difficult to grow or unculturable – T pallidum
lab diagnosis of spirochetes
serological or immunofluorescence tests
spirochete taxonomy and the 3 main types
recognised by cell shape
- identification by sequence of analysis of 16s RNA gene
1) leptospira
2) Borella
3) treptomena
why is the 16s rRNA sequence used for spirochete taxonomy
gene is well conserved due to essential function
what are spirochete cell shape defined by
internal flagella (known axial filaments)
found between membranes
can extend to accommodate flagella
how are spirochetes motile
Counter rotation of the internal flagella filament bundles results in rotation of the cell body
- rotation of the body results in burrowing motility of spirochetes
- therefore they can burrow through tissues
spirochete cell surface components
contains major sheath proteins
periplasmic space is filled with flagellum (also contains peptidoglycan)
No LPS - glycolipids instead
spirochaete diseases
leptospira
boreal
treponema
zoonotic infections
infection of humans via zoonotic vector
e.g. lyme disease
transmission via ticks
Ecotoparasites of many vertebrate species: rodent, deer, birds
stages of infection of borella burgdoferi (zoonotic)
ACUTE
After biting Flu like symptoms often seen
- localised rash (erythema migrans present in 30% cases)
- characteristic bulls – eye rash
- other lesions at sites distal from inoculation occur in 50% of pts
- can live in joints hence arthritis
- slow growers, often chronic
Later
1) neurologic infections
2) Cardiac infections
2) arthalgia and arthritis
borella burgdorferi and virulence factors
Motility considered a major virulence factor
- invades epithelial cells
- No LPS, but numerous outer membrane lipoproteins expressed at different points in infection cycle.
variable surface proteins – antigenic shift
- host mimicry
- copes with low iron levels by using manganese instead of iron as an enzyme co factor
treatment and prevention of borella burgdoferi
- antibiotics (doxycycline 3 weeks)
chronic infections hard to treat as bacteria have become metabolically inert, hide in places with less blood access
LYMErix vaccine - only partially effective
prevention
avoidance of endemic areas
clothing, DEET based repellents
relapsing fever caused by
borelia recurrentitis
transmission via ticks and human body louse
how can relapsing fever occur
antigenic variation
surface protein OspC multiple copies
prevention and control of relapsing fever
- CDC: since most cases occur after sleeping in rodent infested cabins
