- Mucous membrane of the upper respiratory tract of humans.
- Found in the nasopharynx of approx. 75% of healthy peoples.
- Slender, short, gram negative rods or coccobacillus
- 3-0.5 um X 0.5-1 um with rounded ends.
- Prolonged counterstaining for 5-15 minutes with very dilute carbol fuschin often gives satisfactory results.
- Non-Motile, No flagella or pilli
- Capsules are present and important in pathogenicity.
- Encapsulated form are coccobacilli, CSF Sample
- Non-Capsulated are pleomorphic, long, thread, filamentous
- Fastidious Microorganism
- It is the first free living organisms to have its entire genome sequenced; 1,830,140 bp of DNA and 1740 Genes.
- On Blood Agar: translucent, low, convex or flat pin point colonies, Satellitism.
- On Chocolate Agar: Grayish, Transparent, smooth, low, convex or flat with a slightly splayed out, entire edge, mucoid, pale
- In liquid medium like Levinthal’s Broth or Filde’s Broth: Uniform Turbidity.
- 5 to 0.8 mm after incubation at 37˚C for 24 hours, can enlarge upto 1-1.5 mm by 48 hrs.
- Capsulated strains form larger, more opaque, smooth, mucoid colonies, 3-4 mm in diameter.
- Fastidious and Facultative anaerobes and aerobic, grow also in 5% CO2.
- Optimum Temperature: 35-37˚C, Min: 20-25˚C, Optimum pH: 7.6
- Killed at 55˚C for 30 minutes of heating
- Requires 2 accessory growth factors, a head stable growth promoting substances present in Red Blood Cells (X-Factor) and a heat labile vitamin like substances (V-Factor).
- Hemin, plays a role as an enzyme in respiration.
- Use human transferrin as a sole source of iron
- Provide protophyrin IX, iron can be obtained from another source.
- Present in the tissue of plants and animals.
- Heating blood agar to about 75˚C, until it acquires a chocolate agar, releases V-Factor from Red cells and also inactivates NADase activity.
- aureus release V-Factor during growth, which defuses into the surrounding medium, enhancing the growth of H. influenzae.
- influenzae will show Satellitism.
- V-Factor is involved in oxidation-reduction process in the growing bacterial cell.
- influenzae requires pantothenic acid, thiamine and uracil.
- Haemophilus influenza b (Hib) is the major cause of childhood infectious disease.
- It causes meningitis, primary bacteremia, pneumonia, epiglottitis and arthritis.
- Non-Capsulated influenzae (Nc-hi) causes otitis media, conjunctivitis and sinusitis
- Causes chronic bronchitis in adults
Encapsulated organisms –> penetrate the epithelium of the nasopharynx –> invade the blood capillaries –> infection.
- Capsule resists phagocytosis and complement mediated lysis.
- May be opportunistic
- Transmitted by direct contact, inhalation of the respiratory tract droplets.
Specimen: CSF, Sterile site aspirates, fluids, urine, sputum, Respiratory tract specimens.
1. Direct Detection Method
– Gram Staining –>Gram –ve, coccobacilli, small rods
2. Antigen Detection
– Agglutination Assays (Latex Agglutination Test)
– For H. influenzae type b
– On Blood Agar: translucent, low, convex or flat pin point colonies, Satellitism.
– On Chocolate Agar: Grayish, Transparent, smooth, low, convex or flat with a slightly splayed out, entire edge, mucoid, pale.
4. Polymerase Chain Reaction (PCR)
– More sensitive
– CSF is the sample,
– Test in case of meningitis.
- First line of treatment: 3rd Generation Cephalosporin with good CSF penetration.
- Ceftriaxone and Cefotaxime is used in case of Meningitis and Septicemia.
- In poor countries, Chloramphenicol alone or in combination with Ampicillin.
- For non-invasive infections: otitis media, sinusitis, bronchitis: Amoxicillin is used orally.
Prevention and Control
- PRP-conjugate vaccines (capsular antigen)
- PRP-T, PRP-OMP, PRP-CRM, HbOC.