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In 1906, Jules Bordet and Octave
Gengou (another famous Belgian
bacteriologist : 1875-1957) discovered
the microbe that causes whooping
cough (Bordet-Gengou bacillus or
Bordetella pertussis).
Medically Important spp
the genus contains three
medially important species
B. pertussis
B. parapertussis
B. bronchoseptica
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General properties
Morphology and cultural
characteristics
Small gram negative cocco
bacilli
B. parapertussis and B.
bronchoseptica both grow on
sheep BA (SBA) in 1-2 days
Bordetella pertussis
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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.
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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.
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.
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Pertussis toxin
Has one A subunit (toxic part),
plus four different kinds of B
subunits (involved in binding).
Structure of pertussis toxin
A subunit
B subunits
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Activation of pertussis toxin
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.
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Pathogenesis
Respiratory droplet exposure
Enter respiratory tract
Attach to ciliated epithelial cells
Endotoxin inhibits cilia clearance
Replication on outside of respiratory
cells
Cells eventually die and release toxin
Three stages of Whooping
Cough
Catarrhal stage
First stage as bacteria just start to die and
release toxin
Mild cold symptoms, coughing, sneezing
Child is not that sick so parent thinks they
have a common cold and don’t isolate from
other children
This is the MOST contagious stage since
many bacteria still alive in respiratory
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Paroxysmal stage
Maximum cell death and toxin release
Severe Cough
40 – 50 cough spells/day, 20-30 coughs in
a row with no chance to breath
Coughing causes stomach upset and vomiting
Mucous build-up in Lungs
Air blockage can in rare cases lead to death
Secondary pneumonia is biggest threat
Caused by other bacterial pathogens
H. influenzae, S. aureus, S. pneumoniae
Convalescent stage
Coughing spells diminish
slowly
decrease in number of spells
and severity
Possible CNS complications in
some children. The
pathogenesis is not clear
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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.
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!
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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
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.
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B. pertussis pathogenesis
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.
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Specimens: Pernasal swab
from Naso pharyngeal
secretion.
Microscope: B-Pertusis is
small-Non Motile –
capsulated G-Ve
Coccobacilli – Non sporing.
Lab Diagnosis:
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Culture:
B-Pertusis, when culture on
charcoal cephatexin blood Agar
(CCBA) or Bordet – Gengou
pencillin.
It is strike O2 incubation (35 – 37Co)
for 3 days produce mucoid – grayish
– white colonies with shiny surface
and high convex shape (bisected
pearl) or (mercury drop)
appearance
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Biochemical:
we can differential between
species of B-Pertusis by many
test e.g (Motility – Urea –
Oxidase – catalase – pigment
– Producing – Growth on
blood agar.
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B.Pertusis:
Non Motile – catalase +ve –
oxidase +ve urea –ve.
can not grow on blood agar.
not produce pigment.
It differ from Haemophilus
influenzae in it's continued
viability at low temp. (00 – 10C0).
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Serology:
B.Pertusis has three major Ags
(Serotype)
Type 1,2/type 1,2,3/ type 1,3
B. Pertusis can be detected by:
Slide agglutinating.
Immunofluorescent
microscopes.
Complement Fixation.
ELISA.
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B. Parapertusis:
Oxidase –ve - grow rapidy on blood
Agar
Urea +ve - Produce brown Pigment in
N. Agar
Non Motile - it can grow on blood Agar
B. Bronchiseptica:
Motile - it can grow in blood Agar.
Urea +ve - oxidase +ve
Bordetella bronchiseptica
Leifson flagella stain
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Antimicrobial Sensitivity:
Erythromycin –only effective in
early stages of the disease before
the toxin(s) have been released
chloramphenicol.
Tetracycline.
Vaccination
Vaccination (DPT – diphtheria, pertussis,
tetanus)
CNS toxicity was major stumbling block
Blamed on whole cell pertussis prep in the DPT vaccine
Many parents avoided vaccine and apathy led to wide
spread outbreaks
New genetic engineered noncellular preparations
have helped to alleviate fear in parents
However, only effective in 80-85% of children
Therefore, we still need to give antibiotics to
contacts
