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Bordettela

Sharq Elneil College

School of Medical Laboratory Sciences

Department of Microbiology

Medical Bacteriology course

U.Mahadi Hassan Mahmoud Bsc, Msc, MIBMS Microbiology

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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

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Any Questions?