Bordetella, Francisella, and Brucella - PowerPoint PPT Presentation

1 / 33
About This Presentation
Title:

Bordetella, Francisella, and Brucella

Description:

Trachael cytotoxin is related to the B.pertussis peptidoglycan. ... Small g-cb that stain poorly. Brucella. Nonmotile. Nonencapsulated ... – PowerPoint PPT presentation

Number of Views:388
Avg rating:3.0/5.0
Slides: 34
Provided by: unkn1014
Category:

less

Transcript and Presenter's Notes

Title: Bordetella, Francisella, and Brucella


1
Bordetella, Francisella, and Brucella
  • Those Gram-negative bacilli that have no family
    designation

2
Bordetella
  • Classification the genus contains three
    medially important species
  • B. pertussis
  • B. parapertussis
  • B. bronchoseptica
  • Morphology and cultural characteristics
  • Small g-cb
  • B. parapertussis and B. bronchoseptica both grow
    on sheep BA (SBA) in 1-2 days

3
Bordetella
  • B. pertussis for initial isolation (The best
    clinical specimen is a nasopharyngeal swab.) the
    organism requires special media with additional
    nutrients for growth and absorbents to remove
    toxic substances found in complex media such as
    fatty acids and sulfides.
  • Borget-Gengou media contains glycerol, potato
    infusion, albumin (binds fatty acids), and up to
    50 defibrinated SRBCs
  • Charcoal agar supplemented with 10 horse blood
    with or without cephalexin.
  • May take 3-7 days for growth and colonies are
    smooth, raised, and glistening (phase 1
    colonies).
  • They are also hemolytic and produce toxin.

4
Charcoal-horse blood agar
5
Bordetella
  • Upon extensive subculturing, the colonies become
    rough (they progress through phases 2, 3, and
    finally 4) and can now be grown on SBA.
  • They are now less virulent due to loss of
    capsule, hemolytic activity, and toxin
    production.
  • These changes, however, are reversible.
  • The organisms are strict aerobes and grow best
    at 35-370 C.
  • Biochemistry
  • Nonfermentative
  • Use glucose and lactose oxidatively
  • B. bronchoseptica is motile, others are nonmotile
  • B. pertussis is for urease, others are

6
Bordetella
  • No growth on Mac for B. pertussis, others are
    variable
  • Oxidase test is variable
  • Virulence factors (B. pertussis)
  • Pili for attachment
  • Pertactin, an outer membrane protein also acts as
    an adhesion
  • Filamentous hemagglutinin is found on the cell
    surface of and is also secreted.
  • It attaches to cilia by binding to exposed
    lactose receptors.

7
Bordetella
8
Bordetella
  • Pertussis toxin
  • Secreted by type IV secretion system
  • Has one A subunit (toxic part), plus four
    different kinds of B subunits (involved in
    binding).

9
Structure of pertussis toxin
A subunit
B subunits
10
Activation of pertussis toxin
11
Bordetella
  • Once intracellular, the A subunit ADP ribosylates
    a critical cysteine residue on the Gi regulatory
    proteins involved in control of host cell
    adenylate cyclase resulting in increased
    intracellular cAMP.
  • This causes cellular dysfunction.
  • Bacterial adenylate cyclase is secreted and
    inserts into the host cell membrane and is
    activated by intracellular host cell calmodulin
    causing a further increase in the intracellular
    levels of cAMP.

12
Increases in cAMP
13
Bordetella
  • The increase in cAMP from the combined effects of
    pertussis toxin and bacterial adenylate cyclase
    is associate with an inhibition of host cell
    phagocytic cell oxidative responses and the
    inhibition of natural killer cell activity.
  • Dermonecrotic toxin is bacterial cell
    associated and is released upon cell lysis
    causing strong vasoconstrictive effects.

14
Bordetella
  • Trachael cytotoxin is related to the
    B.pertussis peptidoglycan.
  • When this is incubated with cells in culture, the
    cells are destroyed, so it might contribute to
    the killing and sloughing off of ciliated cells
    in the respiratory tract.
  • Lipooligosaccharide associated with the surface
    of the bacteria and has potent endotoxin activity.

15
Bordetella
  • Clinical significance
  • B. pertussis causes whooping cough
  • Acquired by inhalation of droplets containing the
    organism
  • The organism attaches to the ciliated cells of
    the respiratory tract.
  • During an incubation period of 1-2 weeks, the
    organism multiplies and starts to liberate its
    toxins.
  • Next the catarrhal stage occurs - the patient has
    a mild cough and sneezing whereby large numbers
    of organisms are spread through the respiratory
    secretions.
  • This last 2 weeks.

16
(No Transcript)
17
Bordetella
  • Next is the paroxysmal stage that lasts 4-6
    weeks.
  • The patient has rapid, consecutive coughs with a
    rapid intake of air between the coughs (has a
    whooping sound).
  • The ciliary action of the respiratory tract has
    been compromised, mucous has accumulated, and the
    patient is trying to cough up the mucous
    accumulations.
  • The coughs are strong enough to break ribs!
  • Other symptoms due to the activity of the
    released toxins include
  • Increased peripheral lymphocytes due to a
    blocking of homing of lymphocytes to the spleen
    and lymph nodes.
  • Metabolic alteration such as increased insulin
    release and the resulting hypoglycemia
  • Increased capillary permeability and increased
    susceptibility to histamine, serotonin, and
    endotoxin shock

18
Bordetella
  • Finally there is a convalescent stage during
    which symptoms gradually subside.
  • This can last for months.
  • B. pertussis rarely spreads to other sites, but a
    lot of damage may occur, such as CNS dysfunction
    which occurs in 10 of the cases and is due to
    an unknown cause.
  • Secondary infections such as pneumonia and otitis
    media are common.

19
B. pertussis pathogenesis
20
Bordetella
  • B. parapertussis causes a mild form of whooping
    cough
  • B. bronchoseptica
  • Widespread in animals where it causes kennel
    cough.
  • Occasionally causes respiratory or wound
    infections in humans.
  • Treatment
  • Erythromyin only effective in early stages of
    the disease before the toxin(s) have been
    released
  • Vaccination P part of DPT (killed, encapsulated
    organism) a subunit vaccine has also been
    developed (purified pertussis toxin).

21
Francisella
  • Classification only 1 pathogenic species F.
    tularensis
  • Morphology and cultural characteristics
  • Minute, pleomorphic g- rod that stains poorly
  • Staining may be bipolar
  • Nonmotile
  • Nonencapsulated
  • Wont grow on ordinary media requires cysteine
    or cystine for growth

22
Francisella
  • Grow on blood-glucose-cysteine agar
  • Will also grow on Chocolate or MTM with added
    isovitalex
  • Colonies may grow in 24 hours or may take 5-7
    days for growth
  • Is a strict aerobe
  • Biochemistry
  • Oxidase -

23
Francisella
  • No glucose fermentation
  • Wont grow on Mac
  • Diagnosis
  • Is best done by showing an antibody titer
    increase of 140 in a patient not previously
    infected.
  • Culturing the organism is hazardous and should
    only be done under a biosafety hood.
  • The organism is highly contagious and the
    infective dose for an aerosol route of infection
    is very small.

24
Francisella
  • Clinical significance tularemia is a disease
    mostly in rabbits and other rodents.
  • It is usually transmitted to man through skin
    abrasions after exposure to infected animals or
    by ticks or deer flies that have fed on infected
    rodents.
  • It can also be acquired by inhalation or
    ingestion.
  • The manifestations of disease depend upon the
    mode of entry

25
Francisella
  • Entry through skin abrasions (ulceroglandular
    form of the disease) - after 48 hours a lesion
    occurs at the inoculated site.
  • It forms an ulcer and the patient may have
    headaches, pain and fever as adjacent lymph nodes
    become enlarged.
  • If not contained, this can progress to
    septicemia, pneumonia, and abscesses throughout
    the body.
  • The organism survives for long periods of time
    inside phagocytic cells).

26
Skin lesion
27
Francisella
  • Ingestion (typhoidal form of the disease) the
    focus of infection is the mouth, throat, and GI
    tract.
  • Inhalation (pneumonic form of the disease) This
    is the most severe form of the disease and it
    manifests as a pneumonia with a high mortality
    rate of 30 in untreated cases.
  • Antimicrobial susceptibility
  • Streptomycin or tetracycline
  • An attenuated, live vaccine that protects against
    the inhalation form of the disease is available
    for those exposed to the organism.

28
Brucella
  • Classification
  • Are all intracellular organisms
  • 4 species can infect humans
  • B. abortus
  • B. suis
  • B. melitensis
  • B. canis
  • Morphology and cultural characteristics
  • Small g-cb that stain poorly

29
Brucella
  • Nonmotile
  • Nonencapsulated
  • In tissues are found intracellularly
  • Most clinical isolates come from blood cultures
    (Castenadas media which has both a solid and a
    liquid phase)
  • Requires enriched media containing meat infusion
    or tryptone
  • Will grow on CBA or chocolate agar
  • Growth is slow and may take 72 hours
  • Colonies start as tiny pinpoint, translucent
    colonies that become gray with age.

30
Brucella
  • B. abortus requires 10 CO2 for growth, others do
    not
  • Biochemistry
  • Oxidase
  • Nonfermentative
  • Urease \catalase
  • H2S produced by B. abortus and B. suis
  • Speciated based on the ability to grow in the
    presence of the dyes basic fuchsin and thionine

31
Brucella
  • Antigenic structure
  • 2 antigens that are part of the LPS are
    recognized A and M
  • B. melitensis has the highest concentration of M
    and causes the most serious infections
  • Virulence factors
  • Endotoxin
  • Clinical significance
  • Has a tropism for erythritol
  • Animal fetal tissues and placenta, other than
    those in humans, are rich in erythritol and,
    therefore, the organisms often cause abortions in
    these animals.

32
Brucella
  • Causes Brucellosis or undulent fever in man
    following ingestion of contaminated milk or
    cheese from goats (B. melitensis), cows (B.
    abortus), pigs (B. suis), or canines (B. canis).
  • Man can also acquire the organism via contact
    with infected animals.
  • Clinical manifestations range from subclinical,
    to chronic with low grade symptoms of low fever
    and muscular stiffness, to acute with fever and
    chills.
  • The fever typically spikes each evening and this
    coincides with the release of organisms from
    phagocytes (hence the name undulent fever).
  • The patient may also experience malaise,
    weakness, enlarged lymph nodes, weight loss, and
    arthritis.

33
Brucella
  • Antibiotic susceptibility
  • Chemotherapy is difficult because of the
    intracellular survival of the organism.
  • Tetracycline for 21 days, sometimes combined with
    streptomycin.
Write a Comment
User Comments (0)
About PowerShow.com