Spirochaetes Flashcards
Features of spirochaetes
Very unusual bacteria: Gram-negative Very thin- viewed by dark-field microscopy or EM -Spiral shape Varied genome size Many plasmids (large) Virulence factors poorly understood Unique method of motility via internal flagella Anaerobic Slow growing
How to diagnose spirochaetes via a lab?
Relies on serological or immunofluoresence tests
Spirochaete taxonomy?
Recognised by cell shape
Identification by sequence analysis of 16s rRNA gene
What makes spirochaetes different?
Internal flagella = axial filaments
What occurs when deletion of flagella assembly genes occurs?
Aflagellate non-motile strains
No longer corkscrew like = straight rod shaped cells
Occurs for Treponema denticola and Borrelia burgdoferei
How to spirochaetes swim?
Counter-rotation of the internal flagella filament bundles = rotation of cell body = burrowing motility of spirochaetes
What is located on the spirochaete cell surface?
Cell wall components = can modulate immune response, known as major sheath proteins
No LPS - glycolipids
What diseases can spirochaetes cause?
Leptospira = Weils disease Borrelia = Lyme disease, relapsing fever Treponema = ANUG, periodontitis
Zoonotic infections examples?
What do zoonotic infecs have?
Lyme and Weil’s disease
Have an animal reservoir of infec that can under certain circumstances infect humans via a zoonotic vector
Lyme disease cause?
Caused by Borrelia burgdoferi and related sub-species
Features of lyme disease?
Most common zoonootic bacterial infec in europe
Nutritionally fastidious anaerobe
Zoonotic reservoir?
Transmission via lxodes spp. ticks
Ectoparasites of many vertebrate species; rodents, deer, birds
3 life-cycle stages;
- Fed once in each stage; 3-5 days per feed
Bac live and multiply in midgut of ticks
Transmitted via saliva after biting humans
Stages of infec - acute of lyme disease?
Flu-like symptoms
Localised rash
Bulls-eye rash
Stages of infec - later of lyme disease?
Seen from 1 week to 2 years post-infection:
- Neurologic: Meningitis, encephalitis, peripheral neuropathy, cranial-nerve (facial) palsies, vision impairment (chronic)
- Cardiac: myocarditis, blockages
- Athralgia and arthiritis- may persist for months or years - often debilitating- possible autoimmune component – reactivity to surface proteins (OspA)
What causes the later symptoms?
When bac enter sites other than the bloodstream - neurons, joints
Borrelia burgdoferi feautres?
Motility considered a major virulence factor
Invades epithelial cells
Capable of invading many tissue types
No LPS, but numerous Outer membrane lipoproteins OspA-D, expressed at different points in infection cycle. Vls proteins- variable suface proteins- antigenic shift
DbpA- Decorin binding protein, host mimicry?
Copes with low-iron levels by using Manganese instead of iron as an enzyme co-factor
How to prevent lyme disease?
Antibiotics - doxycycline - chronic infecs hard to treat since bac metabolically inert and resides in sites refractory to treatment
Vaccine - to OspA only partly effective (OspA expressed in tick, not humans)
Prevention - avoid endemic areas, clothing, DEEP based repellants
Relapsing fever?
Borrelia recurrentis
Transmitted via ticks and human body louse
Repeated febrile illness
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 infecitons
How to prevent and control relapse?
CDC; check for mice/rodents
Leptospirosis and Weils disease?
Caused by Leptospira interrogans - Leptos (Gr) – ununusually thin spira (la) - colied, spiral Two terminal Periplasmic flagella Present in stagnant water and rivers Infects many mammals Dogs and Rats most important zoonotic reservoir (urine) Enter via broken skin 40- 60 cases/ year in England Outbreaks in walkers, triathlon runners!
Symptoms of leptospirosis (weils disease)?
1-2 week incubation in blood
Leptospirosis: Febrile, flu-like illness with muscle pain, reddening of eyes, and other symptoms such as diarhoea and in some cases meningitis and Hemorrhage in Aqueous humour of eye and CSF
What does weil’s disease cause?
Kidney failure, jaundice and liver failure
Most symptoms due to BV damage
How to prevent and treat leptospirosis?
Rodent controlled
Doxycline
Avoid swimming in infected rivers
What spirohoates cause issues in the mouth? Treatment?
Treponema vincentii = acute necrotising ulcerative gingivitis
Treatment = metronidazole or H202 washes
What organisms are commonly found in periodontal cases?
Treponema denticola
Red complex organisms - (Porphyromonas gingivalis
Tannerella forsythia, Treponema denticola)
Treponema denticola: virulence?
Adherence to basement membrane proteins via 53 Kda Msp : fibronectin, laminin, fibrinogen, type IV collagen and gelatin
Proteases: in-keeping with other periodontal pathogens
CTLP- Chymotrypsin like Protease (Dentilisin), surface exposed in outer membrane: Cleaves transferrin, fibrinogen, fibronectin, IgA, IgG, gelatin
Sialidases:- cleaves surface sialic acid from human cells/ saliva- mutant reduced infection in mice
Motility: tissue invasion and disease progression
Co-adherence with other oral bacteria in mixed biofilm also important (i.e. Pg, Tf, and Fuso’s)
Syphilis: Treponema pallidum treatment?
Treatment with mercury
Name other treponemal diseases and their features
Yaws: T. pertenue - early skin lesions that clear - later destructive lymph - south america and central africa Pinta: T. carateum - again early skin lesions - these progress to chronic disfiguring lesions over time - south and central america
How are treponemal diseases spread?
Skin to skin transmission
How to treat treponemal diseases?
Treatable with penicillin
