This document discusses Haemophilus influenzae, a gram-negative coccobacillary bacteria. It was first isolated in 1892 and thought to cause influenza. There are two main types: unencapsulated and encapsulated strains. Encapsulated type b strains cause more invasive diseases like meningitis while unencapsulated commonly cause localized infections. The document outlines the virulence factors, pathogenesis, clinical manifestations, diagnosis and prevention of H. influenzae infections. It also briefly discusses the HACEK group of bacteria which can cause endocarditis.

1. HEMOPHILUS
By Dr. Rakesh Prasad Sah
Assistant Professor, Microbiology

2. HAEMOPHILUS
• First isolated in 1892 by Robert Pfeiffer – Hence also called Pfeiffer’s bacillus
• Was thought to be the infectious agent for flu
• Was also called Bacillus influenzae
• Common Species
• H. influenzae
• H. parainfluenzae
• H. ducreyi

3. HAEMOPHILUS INFLUENZAE
• Gram negative Rods.
• Range from coccobacillary to long
filamentous forms.
• Non – motile
• Aerobic
• Fastidious organisms

6. HAEMOPHILUS INFLUENZAE
• Two main types:
• I The uncapsulated (untypable) strains
• II The encapsulated strains

7. CAPSULE
• Polysaccharide in nature
• Six types : a, b, c, d, e and f
• Type b is associated with most severe form of disease
• Hib capsule is Polyribitol Phosphate (PRP)

8. VIRULANCE FACTOR
• Outer membrane protein
• Pili
• Immunoglobulin A1 Protease
• Lipopolysaccharides
• Capsule
• Endotoxin

9. VIRULENCE FACTORS FUNCTIONS
Capsular polysaccharides PRP of the capsule is antiphagocytic. It resists
phagocytosis of the bacteria
Lipopolysaccharides Causes meningococcal inflammation
IgA1 protease Causes breakdown of IgA, facilitate colonization of
H. inflenzae on the basis of mucosal surface
Pilli Helps in adherence of H. influenzae to epithelial
cells
Endotoxin Induces host inflammatory response

10. • Humans are the only natural hosts
• Transmission: respiratory droplet spread
• The incidence of Hib fell by 95% in populations with high rates of vaccination

11. PATHOGENESIS
H.Influenzae enters the human host by respiratory route.
Adhesions of the bacteria mediate colonization in
the nasopharynx and oropharynx
Lipid A lipopolysaccharides impairs ciliary function and IgA1 protease
breakdown IgA1
A large bacterial load or the viral infection potentiate the bacterial
infection that invade mucosa and enter the blood stream.
Cause damage of the respiratory mucosa

12. The presence of antibodies, complement components and phagocytes
cause clearance of bacteremia
The absence of anti PRP antibodies contributes to bacterial infection
High grade bacteremia leads to disseminate to various sites including
meninges, subcutaneous tissue,joints,pleura and pericardium
Responsible for causing Meningitis, Arthritis, pneumonia and endocarditis
Colonization of noncapsulated strains will direct extend to sinuses,
eustachian tube etc cause sinusitis and otitis media

13. HAEMOPHILUS INFLUENZAE
Uncapsulated Capsulated
Responsible for localized infections i.e. Responsible for Invasive disease i.e.
Otitis media Meningitis
Conjuctivitis Septicaemia
Brochitis Epiglottitis
Sinusitis Pneumonia
Septic arthritis
Cellulitis

15. CELLULITIS CAUSE BY H.INFLUENZAE IN FOOT

16. CELLULITIS CAUSED BY H.INFLUENZAE IN CHEEK

17. H. INFLUENZAE CAUSING OTITIS MEDIA

18. NON TYPEABLE H. INFLUENZAE
• Otitis media
• COPD
• Pneumoniae in adults underlying COPD or AIDS
• Puerperal sepsis and neonatal bacteremia ( NMF)
• Sinusitis in children and adults
• Rarely invasive infections

19. Features Type b strains Nontypeable strains
Capsule Made up of poly ribosyl ribitol phosphate
(PRP)
Non capsulated
Manifestations Invasive – meningitis, epiglottits,
pneumonia, bacterimia, endocarditis
Noninvasive – otitis media
(children) and penumonia
(adult)
Age Affect children Affect adult
Spread Hematogenous spread Contiguous spread
Vaccine Hib vaccine is available Not available

20. SPECIMEN
• CSF
• Throat Swab
• Sputum
• Pus
• Joint Aspirates
• Pleural Aspirates
• Bronchial Aspirates
• Pericardial Aspirates

23. DIRECT SMEAR OF H.INFLUENZAE IN CSF IN A CASE OF
MENINGITIS

24. H.INFLUENZAE IN IMMUNOFLUORESCENCE MICROSCOPY

25. CULTURAL CHARACTERISTICS
H.Influenzae in Chocolate Agar

26. SATELLITISM
Satellitism Test for H.Influenzae

27. ANTIGEN DETECTION
Latex
Agglutination
Test For H.
influenzae

28. Blood Culture:
• Brain Heart Infusion Broth (BHI Broth)
• Biochemical Reactions
• Catalase
• Oxidase
• Nitrate reduction test
• Serotyping

29. PREVENTION AND CONTROL
Vaccination :
• Purified type b capsular polysaccharide vaccine  18-24 months  2 months interval
• Hib PRP vaccine  type b capsular polysaccharide covalently coupled to protiens such as
diptheria toxoid, tetanus toxoid and N. meningitidis outer membrane protein.
• Rifampicin  4 days to prevent infection in contacts and also to eradicate carrier state.

31. HACEK GROUP BACTERIA
• Highly Fastidious bacteria, slow growing, capnophilic, G –ve, resident of mouth
• Sometimes cause severe infection like endocarditis.
• Species of this group includes
• Haemophilus species : H. aphorphilus, H. paraphrophilus & H. Parainfluenzae
• Aggregatibacter (formerly Actinobacillus) actinomycetemocomitans
• Cardiobacterium hominis
• Eikenella corrodens
• Kingella kingae
• Blood cultures positive after 7-30 days.
• Highly drug resistant so ASTs are essential.