Haemophilus spp

Haemophillus

Sharq Elneil CollegeSchool of Medical Laboratory SciencesDepartment of MicrobiologyMedical Bacteriology course

Mr.Mahadi Hassan MahmoudBsc, Msc, MIBMS Microbiology

History

Hib was found in a group of patients during an influenza outbreak in 1892

Haemophilus influenzae was first isolated in 1890 by Richard Pfeiffer

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Medically important spp

H. Influenzae

H.ducreyi

H. haemolyticus.

H. phrophilus

H.segnis

H.aegyptius (Koch.

Weeks)

H.Para Influenze

H.para haemalyticus

H.araphrophitus

Morphology

Haemophilus influenzae is :

a pleomorphic gram-negative coccobacillus.

H.influenzae may be either encapsulated (typeable) or unencapsulated (nontypeable).

There are six encapsulated serotypes (designated af) that have distinct capsular polysaccharides.

General properties

Extracellular pathogen, does not invade into cells

Fastidious

This means it is difficult to grow

We must give it lots of growth factors

Haemophilus = blood loving

However, this organism can not grow on blood agar alone!

Requires X factor (hematin)

Requires V factors (NAD)

Culture:

Chocolate agar + CO2

Blood culture bottles

Blood agar plate culture of Haemophilus influenzae

X and V factor:

X factor is used by H. influenzae to produce essential respiratory enzyme such as cyto chrome catalase and peroxidase.

V Factor is used as electorn carriers in the organism oxidation reduction system live culture on chocolate (heated blood agar at 75Co - for few minute).

For extra V factor released from RBES on chocolate agar after. Over night. Incubation, H. influenzae strain produce mucoid colonies.

Fig

Species Growth Factor Required

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H. influenzae X + V

H. parainfluenzae V

H. ophrophilus X

H. ducreyi X

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Satellitism

satellitism test when we streak staphaureus (produce V factor) across the surface of on inoculated blood agar plate.

The colonies are largest nearest to the staphylo cocous aureus column of growth than those furthest from it.

Satellitism

Levinthal agar (heated)

The use of transparent media such as levinthal agar (heated) or fildes agar (Peptic digestion) after 24h at 37C

colonies are fishy, seminal smell the colonies of capsulate strain are larger high convex in shape and mucoid and we show ividencence consisting of Red-orange green blue shade which alter with angle of observation.

H. influenzae typing

H. influenzae can be divided into eight biotypes on the basis of three biochemical test (indole production urease activity and ornithine de carboxylase)

this bio typing system is of limited use for epidemiological studies

the majority clinical isolate are distributed between three bio type (I, II, III) invasive type b strains are of biotype, I.

VIRULENCE FACTORS

i. Capsule:

ii. Outer membrane components:OMP & LOS

iii. Adherence:

iv. IgA proteases:

Virulence Factors

Fimbriae for attachment to respiratory tract cells

Capsule is produced to prevent phagocytosis

Endotoxin which is part of ALL Gram-negative cells

Helps respiratory tract colonization by blocking cilia clearance

Induces inflammation at site of infection

Causes disease by simply being in the environment and sparking inflammation through endotoxin

Transmission:

Transmission occurs through direct contact with respiratory droplets from nasopharyngeal carrier or case patient.

Neonates can acquire infection by aspiration of amniotic fluid or contact with genital tract secretions containing the bacteria.

Pathogencity of Haemophilus

Is divided to capsulate and Non capsulate

Capsulated strains could be differentiated serological into 6.type labeled (a F).

The most serious strain is type b which cause:

Pyogenic (purulent) meningitis in young children (2 month to 3 years) olds

Acute epiglotitis (group) (2 7 years ols)

Cellulitis pyogemic ar thritis, osteitis) conjunctivitis, middle ear infections, and pneumonia.

On Capsulated H. Influenzae strains are associated with less severe but often persistent infections such as

purulent exacerbations of chronic bron chitis (Mainly in adult),

conductivities middle ear infection

paranasal sinusitis Non capsulated of H. Influnzae and some other species form.

Haemophilus influenzae

Systemic infections (meningitis)

Caused by encapsulated strains

Prior to the development of the new conjugate vaccines, 1 in 200 children got the disease

65% of cases were in kids