Unit 2: Bacteriology
118
Lecture 8 – Bordetellae
1. Bordetella pertussis:
Causes whooping cough (pertussis).
Morphology:
Minute G-, nonmtile encapsulated coccobacilli
toluidine blue stain → bipolar metachromatic granules
Culture: Strict aerobic requires enriched media:
1) Bordet-Gengou (potato-blood-glycerol) agar + penicillin
G or Regan-Lowe medium.
2) BCYE (buffered charcoal-yeast extract) agar.
Incubation at 35-37Cº for 3-7 days in a moist
environment & identified by IF staining.
Hemolysis of blood is associated with virulent pertussis.
Antigenic Structure
B. pertussis produces many factors that are involved in
the pathogenesis:
1) Pili: adherence of bacteria to the ciliated epithelial cells
of upper R.T.
2) Tracheal cytotoxin: inhibits DNA synthesis in ciliated
cells =
3) LPS: causing damage to the epithelial cells of upper R.T.
4) five virulence factors regulated by vir or bvg (bordetella
virulence gene):
a. Filamentous hemagglutinin: mediates adhesion to
ciliated cells.
b. Pertussis toxin: a protein consists of 2 subunits A & B
has similar action of cholera toxin & promotes
lymphocytosis, sensitization to histamine, enhanced
insulin secretion & has ADP-ribosylating activity.
c. Adenylyl cyclase toxin.
d. Dermonecrotic toxin.
e. Hemolysin.
Pathogenicity:
Transmitted by respiratory route from carriers or early
cases, adheres to & multiplies on the epithelial surface of
trachea & bronchi & interferes with ciliary action (no blood
invasiveness), liberate toxins & substances that irritate
surface cells → coughing & lymphocytosis may be necrosis
& PMNs infiltration peribronchial inflammation &
pneumonia (secondary invaders like staphylococci & H.
influenzae may cause pneumonia) obstruction of smaller
bronchioles by mucous plugs & oxygenation of blood →
causing whooping cough (in infants).
Clinical Findings:
After incubation period (2weeks) →catarrhal stage: mild
coughing, sneezing & large No. of bacteria in droplets of
patient (highly infectious but not very ill) → paroxysmal
stage: explosive cough & characteristic whoop upon
inhalation → rapid exhaustion may associated with
vomiting, cyanosis & convulsions. Rarely become fatal
complication of encephalitis.
WBC`s count high (16000-30000/μL) with lymphocytosis.
Several types of adenovirus & Chlamydia pneumoniae can
produce a similar clinical picture of B. pertussis.
Unit 2: Bacteriology
119
Diagnostic Lab
Specimen: saline nasal wash, nasopharyngeal swabs or
cough droplets (onto a cough plate).
Direct fluorescent Ab (FA) test: FA reagent used to
examine nasopharyngeal swab & to B. pertussis after
culture on solid media.
Culture: Bordet-Gengou medium or BCYE medium →
identified by IF staining or by slide agglutination with
specific antiserum.
PCR test: for B. pertussis & B. parapertussis.
Immunity:
The 1
st
defense against B. pertussis infection is the Ab that
prevents attachment of bacteria on the cilia of the
respiratory epithelium.
After recovery & vaccination 2
nd
infections may occur but
mild. Reinfections may occur years later in adults that may
be sever.
Pertussis vaccine: using toxin-producing phase I cells →
acellular pertussis vaccines contains 3-5 Ags.
Treatment:
Erythromycin during catarrhalstage to elimination of
bacteria, as a prophylactic & prevent paroxysmal stage.
Oxygen inhalation to prevent anoxic damage to the brain.
Epidemiology, Prevention & Control:
Worldwide, the source of infection is the patient in the
catarrhal stage. Most cases in children less than 5 years &
the most deaths occur in the 1
st
year of life. So every infant
should receive 3 injections of pertussis vaccine during the
1
st
year followed by a booster of 5 doses.
Pertussis vaccine administered in combination with toxoid
of diphtheria & tetanus (DTP).
Prophylactic: erythromycin for 5 days benefits to infants &
exposed adults.
2. B. parapertussis:
produce disease similar to whooping cough, it has a silent
copy of the pertussis toxin gene. Grows more rapidly than
B. pertussis produces larger colonies.
3. B. bronchiseptica (bronchicanis):
found in the R.T. of canines, causes diseases in animals &
pertussis- like illness in humans a chronic R.T. infections. It
has a silent copy of the pertussis toxin gene.