small gram negative bacteria l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Small Gram negative bacteria PowerPoint Presentation
Download Presentation
Small Gram negative bacteria

Loading in 2 Seconds...

play fullscreen
1 / 31

Small Gram negative bacteria - PowerPoint PPT Presentation


  • 363 Views
  • Uploaded on

Small Gram negative bacteria. Brucella. Small Gram negative, coccobacilli Non-motile, aerobic, non-fermentative Obligate intracellular Oxidase and catalase positive Visualised by Kosters (modified –ZN) stain Require growth on complex media

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 'Small Gram negative bacteria' - athalia


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
brucella
Brucella
  • Small Gram negative, coccobacilli
  • Non-motile, aerobic, non-fermentative
  • Obligate intracellular
  • Oxidase and catalase positive
  • Visualised by Kosters (modified –ZN) stain
  • Require growth on complex media
  • Growth enhanced by CO2 (some require CO2 for growth)
  • Species identified by growth characteristics and serotyping
  • Predilection for male and female reproductive tracts in animals and cause reproductive disease in mammals
  • Notifiablecategory 3zoonosis
diagnosis
Diagnosis
  • Specimens:
    • Liquid specimens can be incubated straight.
    • Scrapings from cotyledons and tissues are homogenised.
    • Specimens include urine (males), milk, blood, vaginal swabs, etc.
    • Grow at 37°C for 4-15 days.
  • Direct microscpy:
    • From cotyledons using modified Zeihl-Nelsen (MZN) stain (also known as Koster stain).
diagnosis4
Diagnosis
  • Require enriched media to grow.
    • E.g. blood agar, liver infusion, tryptose, etc
  • Colonies are pinpoint, round, smooth, glistening, translucent and non-haemolytic.
  • Biochemical tests:
    • Oxidase (except B. ovis), Catalase positive.
    • Urease (except B. ovis) positive.
    • Indole negative.
    • Reduce nitrate.
  • Serological tests:
    • E.g. serum agglutination test (SAT).
koster s stain
Koster’s stain

1. Flood the slide with dilute carbol fuchsin and let it act for 5-7 minutes.

2. Wash with water.

3. Decolourise with 0.25% acetic acid for up to 30 seconds. The film should be colourless or very faintly pink.

4. Wash with water.

5. Counterstain with Loeffler’s methylene blue and leave for ½-1minute. Brucellae appear as little red bacilli singly, in pairs and in clusters.

brucella pathogenesis

Lysosome

Phagolysosome

fusion

Acidification

Prevent fusion

Brucella sp.

Phagosome

H+

Brucella pathogenesis

Brucella are facultative intracellular pathogens

pathogenesis of brucellosis
Pathogenesis of Brucellosis
  • Penetrate mucosa
  • Regional LN
  • Phagocytosis/invasion
  • Proliferation/ Persistence
  • Bacteraemia
  • Dissemination

Udder

excretion

Testis

Uterus

Placentitis

& abortion

Persistence

b melitensis genome
B.melitensis genome
  • 2 chromosomes!
  • Lacking many expected virulence systems
    • Type III secretion systems
    • Fimbriae
    • Toxins
    • Capsule
  • Putative virulence genes identified
    • Type IV secretion system
brucella pathogenesis13
What we know about Brucella virulence – very little.

Intracellular pathogen – many cell types

Survives within macrophages

Inhibits phagolysosome fusion

Tissue tropism - erythritol

Erythritol preferred carbon source

Present in high concentration in placenta of cattle, sheep, goats and pigs.

Siderophore, iron-uptake

Brucella pathogenesis
brucella persistent infection
Brucella: persistent infection
  • Survival within macrophages
    • Inhibits phagolysosome fusion
    • Type IV secretion system
  • Don’t alarm the host
    • Brucella LPS 1000 times less pro-inflammatory than E.coli LPS
bovine brucellosis eradication
Bovine brucellosis: Eradication
  • 1934 ~ 40% of cattle herds Brucella positive
  • A free calf vaccination scheme, S19 vaccine, 1962.
  • Voluntary attested herds scheme, 1967.
  • Compulsory area eradication, 1971.
  • Disease-free, vaccination programme ended 1979
  • Brucellosis-free status gained from EU, 1991.
brucella screening
Brucella screening
  • Usually serology – many different tests
  • Detect antibody in serum (milk) against Brucella LPS
  • Tests
    • Milk ring test
    • Rose Bengal plate test
    • ELISA
    • Serum agglutination test (SAT)
  • False positives
    • Antibodies cross react with LPS of other bacteria
    • Yersinia enterocolitica O9
brucella vaccines

O side-chain

Core

Lipid A

Brucella vaccines
  • Live vaccines, not genetically defined
  • “Smooth” strains
    • B.abortus S19 - Cattle
    • B. melitensis Rev.1 -sheep goats
  • “Rough” strains
    • B.abortus RB51 rifampicin R - Cattle
  • Problems
    • Anti-LPS antibodies – screening
    • Infection of humans
bordetella
Bordetella
  • Small gram negative coccobacilli
  • Strictly aerobic
  • Oxidase and catalase positive
  • Motile (except B.pertussis and B.parapertussis)
  • Don’t ferment carbohydrates (growth is strongly inhibited in acidic medium)
  • Grow on MacConkey (except B.pertussis and B.parapertussis)
  • Respiratory tract pathogens mammals and birds
diagnosis22
Diagnosis
  • Culture on blood agar for 24-48h.
  • Colonies are pinpoint and smooth.
  • Growth on the selective Smith-Baskerville (SB) medium is enhanced. Colonies appear green surrounded by bluish discolouration.
bordetella virulence factors

Fimbriae

Attach to

host tissues

Adhesins

Filamentous

Haemagglutinin (FHA)

Pertactin

Adenylate cyclase toxin

Tissue damage

Counteract

host defences

Toxins

Tracheal cytotoxin

Dermonecrotic toxin

Type III secretion system

Bordetella virulence factors
slide27

Adenylate cyclase toxin

  • Tracheal cytotoxin (TCT)
  • Adenylate
  • cyclase
  • RTX
  • toxin
  • TCT
  • LPS
  • Nitric oxide

calmodulin

[cAMP]

  •  Phagocytosis
  •  Chemotaxis

Exotoxin & adhisin

regulation of bordetella virulence

Virulence genes

expressed

BvgA

P

37OC

25OC

Mutation

Virulence genes

not expressed

BvgA

Virulence genes

never expressed

Regulation of Bordetella virulence

Temp

BvgS

BvgA

pathogenesis

PMT

Destruction of

turbinates

Initial attachment

of B. bronchiseptica

to ciliated cells.

Tight adhesion to cilia.

Production of toxins.

Paralyse cilia

  • Colonisation with toxigenic
  • P.multocida types A or D
Pathogenesis

Loss of cilia.

Interference with innate

and specific immune response.

Accumulation of mucus.

moraxella bovis
Moraxella bovis
  • Gram negative short plump rods often in pairs
  • Strict aerobe, “twitching-motility”
  • Oxidase and catalase positive
  • Do not grow on MacConkey. Do not utilise sugars
  • Urease and nitrate negative
  • Infectious bovine keratoconjunctivitis, (new forest eye, pink eye)
  • Virulence factors
    • Fimbriae (pili)
    • Haemolysin – RTX toxin
    • Lactoferrin + transferrin binding protein – Fe uptake
    • Capsule, degradative enzymes