slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Borrelia species PowerPoint Presentation
Download Presentation
Borrelia species

Loading in 2 Seconds...

play fullscreen
1 / 19

Borrelia species - PowerPoint PPT Presentation


  • 139 Views
  • Uploaded on

Borrelia species. 1. 3-20 x 0.2-0.5 um, more irregular than treponemes 2. Can be stained in appropriate specimens (e.g. blood) using Giemsa 3. Number of axial filaments depends on species (e.g. 12 for B. recurrentis ) 4. Microaerophlic, nutritionally fastidious but grow slowly in vitro

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Borrelia species' - efrem


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Borrelia species

1. 3-20 x 0.2-0.5 um, more irregular than treponemes

2. Can be stained in appropriate specimens (e.g. blood) using Giemsa

3. Number of axial filaments depends on species (e.g. 12 for B. recurrentis)

4. Microaerophlic, nutritionally fastidious but grow slowly in vitro

5. Either louse-borne (B. recurrentis) or tick-borne (e.g. B. hermsii, B. perkeri, B burgdorferi, etc.)

6. Currently 18 recognized species

7. Cause relapsing fevers or Lyme disease

slide2

Relapsing fever Borrelias

1. Possess a linear chromosome and plasmids (up to 14 plasmids per bacterial cell

2. Tick is the vector and injects bacteria into bloodstream after biting

3. Disseminated throughout the body

4. Causes high fever approx. 5-7 days post-infection, followed by subsidence and then subsequent relapse with fever.

5. Cycle may continue hence the name “relapsing fever”

slide4

Relapsing fever Borrelias (contd.)

6. Demonstrate antigenic variation

#s Borrelia

10

7

10

7

10

7

Serotype specific IgM

Sero. 7

Sero. 21

Sero 14.

Anti 7

Anti21

Anti14

1 1.5 2 2.5

Weeks post infection

slide5

Relapsing fever Borrelias (contd.)

7. Variation are in the variable major proteins (VMP) of the outer membrane. Two families of proteins - variable small amd variable large protein (Vsp and Vlp respectively)

8. Vsp (20kDa) and Vlp (36kDa) are lipoproteins anchored to the membrane via their lipids

9. VMPs may be involved in tissue tropism

slide6

10. Clearing in vivo occurs through complement-mediated lysis

11. The genes encoding the VMPs are located on plasmids and the chromosome.

12. A single bacterial cell can only express one antigenic type of VMP

13. How are genes activated to alter the antigenic profile of a bacterium?

slide7

p

1

p

p

p

2

p

p

p

3

p

+

p

4

p

Barbour & Restrepo (2000): Emerging Inf. Dis.6:451

slide8

VMP gene structure

1. The genes encoding the VMPS (vlp and vsp genes) share common properties facilitating recombinaion.

5’

3’

Constant

Variable

Constant

2. Upstream homology region is 50bp from 5’ region

3. Downstream homology site is 1kbp from 3’ end of gene

slide9

Borrelia direct repeat (Bdr) proteins

1. Bdr genes are found in all Borrelias

2. Sequence analysis indicates conserved functionaldomains

3. Precise function is unknown; signaling molecules??

slide10

Epidemiology of relapsing fever

1. Seasonal incidence in the US

2. Associated with campers, backpackers, etc.

3. Humans are incidental hosts for most relapsing fever Borrelias

4. Transmission by infected tick bite

5. B. recurrentis is a louse-borne disease of humans with interhuman transmission

6. Endemic in underdeveloped countries and associated with poverty and overcrowding

slide11

Lyme disease borreliosis

1. Caused by B. burdorferi

2. First recognized in 1977 among children in Lyme, Conn. believed to be suffering from rheumatoid arthritis

3. Begins as a localized skin infection but may spread as a second phase after latency involving multiple system (c.p. syphilis)

4. Reservoir of infection - Infected animals (deer & mice)

Tick (Ixodes dammini) vector

slide12

Borrelia burdorferi

1. Long slender spirochetes (20-30 x 0.2-0.3 microns)

2. 7-11 axial filaments

3. Possesses a linear chromosome as well as linear and circular plasmids

4. Does not demonstrate extensive antigenic variability

5. Linear plasmids encode two major outer surface lipoproteins, OspA and OspB.

slide13

B. burgdorferi Virulence

1. Initial adherence to host tissues

In vitro B. burgdorferi bind to many cell types via integrins and glycosaminoglycans.

2. Multiple binding pathways or a single promiscuous pathway?

3. Observed binding specificities among different strains of B. burgdorferi may indicate differences in binding components

slide14

B. burgdorferi virulence contd.

4. Infection is frequently characterized by bacteria/ECM association.

5. Decorin is a host-cell, collagen-associated protein to which

B. burgdorferi binds

6. Two bacterial porteins, DbpA and DbpB, mediate adherence to decorin

slide15

DbpA and B

1. Encoded by a large (approx. 54kbp) linear plasmids

2. Outer membrane proteins

3. Not homologous to other known adhesins

4. Following invasion into the connective tissue these proteins may play a role in establishment and spread of bacteria.

5. Have been considered as immunogens for vaccination.

6. Decorin regulates collagen fibril formation, inactivation of C1q, cell growth, etc.

7. Dbps could play a role in mediating inflammation

slide16

Interaction with finbrocytes

1. Fibrocytes express fibronectin and collagen, they target to connective tissue and recruit T cells. Therefore, they may play a role in mediating inflammation in connective tissue

2. B. burgdorferi bind, in vtiro, to finbrocytes

3. Bacteria reside deep within membrane invaginations without being phagocytosed

4. Location of binding may protect bacteria from immune system

5. Bacteria may coat themselves in host cell membrane (i.e. mimicry)

slide17

Epidemiology

1. One of the most common spirochetal diseases in US

CDC, 2000

slide18

Epidemiology contd.

2. Seasonal incidence

CDC, 2000

slide19

Epidemiology contd.

3. Most cases are associated with the eastern seaboard states, upper midwest, and west

4. Most reliable clinical marker is the erythema migrans that occurs in 60-80% of infections

5. Cases confirmed by either isolation form clinical specimen OR demonstration of diagnostic levels of IgM and IgG

6. LYMErix is an rOspA-based vaccine