Spirochaetes Flashcards
(18 cards)
Spirochaetes
- Gram -ve
- Very thin, viewed by dark-field microscopy or EM
- Spiral shape
- Varied genome size
- Many large plasmids
- Motility via internal flagella
Many are difficult to grow:
3 main disease causing Spirochaetes
• Leptospira
- weils disease
- leptospirosis
• Borrella
- lyme disease
- relapsing fever
• Treponema
- syphillis
- ANUG
- periodontitis
Flagella genes
Deletion of a flagella gene can hinder the spirochaete from swimming and results in non-motile strains (flaB & flgE)
These strains are no longer corkscrew like, they become straight rod shaped cells
How do Spirochaete’s swim
- Counter-rotation of the internal flagella filament bundles results in rotation of the cell body
- Rotation of the body results in burrowing motility of Spirochaetes
The Spirochaete cell surface
- Cell wall components are able to modulate immune response - known as Major sheath proteins (Msp)
- NO LPS - glycolipids
What are zoonotic infections
Infections with ANIMAL involvement.
They have an animal reservoir of infection that can infect humans via a zoonotic vector
• Both Lyme and Weil’s disease are examples of zoonotic infections (like plague)
What is Lyme Disease
• Caused by Borrelia burgdoferi
- Most comon zoonotic infection in Europe
- Small spirochaete only viewed by EM and Dark-field microscopy
- Nutritionally fastidious anaerobe
Zoonotic Reservoir (Lyme diseae)
• Transmission via ticks
- take blood from mammals (rodents, dears)
- Find blood host to boost energy at each stage (3 life-cycle stages)
- Its the injected saliva on the bite that contains this organism that infects the human
- Early in infection: penetration of vessels & dissemination
- Late in infection: Penetration of tissues and establishment of infections in heart, joints, skin: Arthritis & facial palsy may ensue
Characteristics of Lyme Disease infection (ACUTE early stage)
- Flu-like symptoms often seen
- Localised rash: Erythema migrans present in 30% cases
- Characteristic BULLS-EYE RASH
LATER stage of infection in Lyme disease)
1 week - 2 years (ability to move allows it to go around body)
• Neurologic:
- meningitis
- peripheral neuropathy
- facial nerve palsies
- vision impairment
• Cardiac:
- myocarditis
- blockages
- No LPS but numerous outer membrane lipoproteins that are variable (OspA-D)
- Human protein look-a-like (DbpA)
- Copes with low-iron levels by using manganese instead of iron as an enzyme co-factor
Prevention & Treatment of Lyme disease
• Treatment:
- antibiotics
- doxycycline
- chronic infections hard to treat
• Vaccine:
- To OspA only partly effective.
• Prevention:
- Avoidance of endemic areas
- Clothing, DEET based repellants
Relapsing Fever
• Borrelia recurrentis
- transmitted via ticks
- initial infection cleared, but antigenic variation by the bacterium starts a new set of symptoms
- 3-10 episodes
- can infect liver/spleen
How could it relapse?
• Antigenic variation - surface protein OspC multiple copies - expressed variably in recurring infections
Leptospirosis and Weil’s disease
• Caused by Leptospira interrogans
- Two terminal periplasmic flagella
- Present in stagnant water & rivers
- Infect many mammals
- Dogs & Rats most important in zoonotic reservoir (urine)
- enters via broken skin
Symptoms of Leptospirosis & Weil’s disease
• Leptospitosis
Flu-like illness
- muscle pain
- redding of eyes
- diarrhoea
- can cause meningitis and haemorrhage
10-15% of cases develop Weil’s disease:
- kidney failure
- jaundice & liver failure
- most symptoms caused by damage to blood vessels
PREVENTION & TREATMENT:
- Rodent control
- Doxycycline
- Avoid swimming in infected rivers
Spirochaetes in the mouth
Treponema Vincentii:
- Acute necrotising Ulcerative Gingivitis
Treated by metronidazole or Hydrogen peroxide washes
Treponema denticola, Red complex organisms & periodontitis
• These 3 organisms are most commonly found in periodontal cases (bone loss, pocket formation)
Porphyromonas gingivalis
Tannerella forsythia
Treponema denticola
Virulence of Treponema Denticola
• Adherence to basement membrane proteins via 53 Kda:
- fibronectin, fibrinogen, type IV collagen, gelatin
PROTEASES:
SIALIDASES:
- cleaves surface silica acid form human cells/saliva
MOTILITY
CO-ADHERENCE
