Haemophilus influenzaeHaemophilus influenzae

The genus haemophilus organisms are small The genus haemophilus organisms are small

gram negative cocco-bacilli (because rounded gram negative cocco-bacilli (because rounded

at ends).at ends).

Long filamentous forms also seen. Long filamentous forms also seen.

Some strains are capsulated. Some strains are capsulated.

The commonest is Haemophilus influenzae.The commonest is Haemophilus influenzae.

The other species of the genus haemophilus The other species of the genus haemophilus

are.are.

1. H. ducreyi1. H. ducreyi

2. H. parainfleunziae 3. H. aegyptius2. H. parainfleunziae 3. H. aegyptius

PropertiesProperties:: It is a gram negative rod ( coccobacillus).It is a gram negative rod ( coccobacillus).

A facultative anaerobe which grows best in A facultative anaerobe which grows best in

media enriched with comedia enriched with co22..

Temperature requirements 32-37 degree Temperature requirements 32-37 degree

celciuscelcius

Has got a polysaccharide capsule.Has got a polysaccharide capsule.

Non capsulated forms also exist.Non capsulated forms also exist.

On the basis of type of capsule there are six On the basis of type of capsule there are six

serotypes numbered as a,b,c,d,e and f.serotypes numbered as a,b,c,d,e and f.

Serotype b is most virulent typeSerotype b is most virulent type

Organism found only in humans.Organism found only in humans.

PathogenecityPathogenecity:: Enters the body through respiratory tractEnters the body through respiratory tract

Two types of behaviours.Two types of behaviours.

11. . Asymptomatic colonizationAsymptomatic colonization

2. Infections such as sinusitis, otitis media 2. Infections such as sinusitis, otitis media

or pneumonia.or pneumonia.

Organism produces IgA protease whichOrganism produces IgA protease which

neutralizes respiratory mucosal IgA.neutralizes respiratory mucosal IgA.

This helps in its attachment to This helps in its attachment to

respiratory mucosa.respiratory mucosa.

After attachment to respiratory mucosa it After attachment to respiratory mucosa it

can enter blood stream and cause.can enter blood stream and cause.

Bacteremia and meningitis.Bacteremia and meningitis.

95% of encapsulated forms (type 95% of encapsulated forms (type

b) responsible for these diseases.b) responsible for these diseases.

Non capsulated forms are responsible for Non capsulated forms are responsible for

otitis media, sinusitis and pneumonia.otitis media, sinusitis and pneumonia.

In children the age group 6 months -6 In children the age group 6 months -6 years is most prone to infection by the years is most prone to infection by the organism.organism.

Peak incidence is from 6 months- 1 year.Peak incidence is from 6 months- 1 year. Virulence factors are polysaccharide Virulence factors are polysaccharide

capsule and endotoxin.capsule and endotoxin.

Clinical featuresClinical features::

1.Meningitis is same in features to that 1.Meningitis is same in features to that

caused by meningococcus and caused by meningococcus and

pneumococcus except that the onset of pneumococcus except that the onset of

other symptoms along with drowsiness other symptoms along with drowsiness

is rapid.is rapid.

2.Otitis media and sinusitis cause pain in 2.Otitis media and sinusitis cause pain in

affected areas and redness and bulging affected areas and redness and bulging

of tympanic membrane.of tympanic membrane.

3.Septic arthritis, cellulitis and sepsis3.Septic arthritis, cellulitis and sepsis

(specially in splenectomized patients).(specially in splenectomized patients).

4.Rarely epiglotitis in young children.4.Rarely epiglotitis in young children.

5.Pneumonia in elderly specially those with 5.Pneumonia in elderly specially those with

chronic respiratory disease.chronic respiratory disease.

Lab diagnosisLab diagnosis::

Gram stainingGram staining

Organism is grown on chocolate agar.Organism is grown on chocolate agar.

Chocolate agar is enriched with two factors.Chocolate agar is enriched with two factors.

1. Factor X (haematin)1. Factor X (haematin)

2. Factor V (NAD).2. Factor V (NAD).

Other species do not require both factorsOther species do not require both factors

The colonies will be greyish-white, small and The colonies will be greyish-white, small and

mucoid.mucoid.

Definitive diagnosis can be made with Quellung Definitive diagnosis can be made with Quellung

testtest

Additional means of identifying encapsulated Additional means of identifying encapsulated

strains include fluorescent-antibody staining of strains include fluorescent-antibody staining of

the organism and latex agglutination tests, the organism and latex agglutination tests,

which detect the capsular polysaccharide.which detect the capsular polysaccharide.

TreatmentTreatment:: Ceftriaxone is drug of choice in meningitis Ceftriaxone is drug of choice in meningitis

and other serious infectionsand other serious infections Otitis media and sinusitis are treated with Otitis media and sinusitis are treated with

co-amoxiclav.co-amoxiclav. PreventionPrevention:: It is by vacination.It is by vacination. The vaccine given is called HibThe vaccine given is called Hib It is in conjugated form. Conjugated with It is in conjugated form. Conjugated with

a carrier protein.a carrier protein.

Given in between 2-15 months.Given in between 2-15 months.

Conjugated is more effective than un Conjugated is more effective than un

conjugated one.conjugated one.

Rifampicin is given in close contactsRifampicin is given in close contacts

BordetellaBordetella

The genus Bordetella contains seven species. B. pertussis is by far the most important causative agent of whooping cough

Other important ones are B. parapertussis, B. bronchoseptica.

Properties: B. pertussis is a tiny (0.5 to 1.0 m),

gram-negative cocco-bacillary rod.

EncapsulatedEncapsulated

Obligate aerobeObligate aerobe

The organism is also very susceptible to

environmental changes and survives for

little time outside the human respiratory

tract.

Oxidase and Catalase positive.

The pilli of cell wail contain a protein

called filamentous haemagglutinin(fha)

EpidemiologyEpidemiology:: B. pertussis is spread by droplets

produced by patients in the early stages of illness. It is highly contagious, infecting 80 to

100% of exposed susceptible persons. Pathogenesis: B. pertussis is a strict human pathogen Primarily a disease of infants and Primarily a disease of infants and

childrenchildren

The organism attaches to the respiratory The organism attaches to the respiratory

mucosa with the help of filamentous mucosa with the help of filamentous

haemaglutinin (fha).haemaglutinin (fha).

Once attached, the bacteria immobilize

the cilia and begin a sequence in which

the ciliated cells are progressively

destroyed and extruded from the

epithelial border

B. pertussis does not directly invade the cells of the respiratory tract or spread to deeper tissue sites.

Including filamentous haemagglutinin it produces four virulence factors.

1.Pertussis toxin ( Exotoxin) is a single antigen causing local tissue damage associated with inflammation.

This exotoxin has a B subunit that binds to target cell receptors, "unlocks" the cell, allowing entry of the A subunit.

The A subunit activates cell-membrane-

bound G regulatory proteins,which in turn

activate adenylate cyclase. This results in

production and outpouring of cAMP,

which activates protein kinase and other

intracellular messengers.

It causes promotion of lymphocytosis and

inhibition of phagocytosis.

2.Extra cytoplasmic adenylate cyclase:

The organisms also synthesize and export The organisms also synthesize and export

adenylate cyclase. This enzyme, when adenylate cyclase. This enzyme, when

taken up by phagocytic cells can inhibit taken up by phagocytic cells can inhibit

their bactericidal activity. their bactericidal activity.

3)Tracheal cytotoxin: is a fragment of the is a fragment of the

bacterial peptidoglycan that damages bacterial peptidoglycan that damages

ciliated cells of the respiratory tract. ciliated cells of the respiratory tract.

Tracheal cytotoxin appears to act along Tracheal cytotoxin appears to act along

with endotoxin to induce nitric oxide, with endotoxin to induce nitric oxide,

which kills the ciliated epithelial cells.which kills the ciliated epithelial cells.

Clinical FindingsClinical Findings:: Whooping cough is an acute Whooping cough is an acute

tracheobronchitis that begins with mild tracheobronchitis that begins with mild

upper respiratory tract symptoms upper respiratory tract symptoms

followed by a severe paroxysmal cough, followed by a severe paroxysmal cough,

which lasts from 1 to 4 weeks.which lasts from 1 to 4 weeks.

Occurs in three distinct stages:Occurs in three distinct stages:

Catarrhal stageCatarrhal stage:: mild upper respiratory mild upper respiratory

tract infection tract infection

Paroxysmal stageParoxysmal stage:: extends to the lower extends to the lower

respiratory tract, with severe cough respiratory tract, with severe cough

Convalescent stageConvalescent stage:: less severe cough less severe cough

that may persist for several months that may persist for several months

Lab diagnosisLab diagnosis:: Gram staining.Gram staining. The organism can be isolated from The organism can be isolated from

nasopharyngeal swabs taken during the nasopharyngeal swabs taken during the paroxysmal stage. Bordet-Gengou paroxysmal stage. Bordet-Gengou medium or Regan-Lowe is used for the medium or Regan-Lowe is used for the culture.culture.

Direct fluorescent-antibody staining of Direct fluorescent-antibody staining of the nasopharyngeal specimens is often the nasopharyngeal specimens is often used for diagnosis. used for diagnosis.

Polymerase Chain ReactionPolymerase Chain Reaction Treatment:Treatment: Erythromycin reduces the number of Erythromycin reduces the number of

organisms in the throat and decreases organisms in the throat and decreases the risk of secondary complications the risk of secondary complications

Prevention:Prevention: By vaccinationBy vaccination