haemophilus influenzae. the genus haemophilus organisms are small gram negative cocco-bacilli...
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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
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
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