Haemophilus influenzae B. Coloured Transmission Electron Micrograph (TEM) of a single Haemophilus influenzae type B bacterium. In cross-section the outer cell wall of the bacterium is seen, with DNA genetic material (blue) in the core. It is rod- shaped, and a Gram-negative bacillus. Haemophilus influenzae is an important pathogen in children aged 1-5 years old. It colonizes the upper respiratory tract within the first few months of life. It may spread locally to cause respiratory tract diseases like bronchitis and pneumonia. The type B (HIB) serogroup of this bacteria is the most common cause of epiglottitis and paediatric meningitis. Magnification: x20,000 at 6x7cm size.