Haemophilus and Legionella

Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the Pasteurellaceae family. These organisms inhabit the mucous membranes of the upper respiratory tract, mouth, vagina, and intestinal tract. The genus Haemophilus includes a number of species that cause a wide variety of infections but share a common morphology and a requirement for blood-derived factors during growth that has given the genus its name.The impotant one and the major pathogen is Haemophilus influenza.
Other Haemophilus species cause disease less frequently. Haemophilus parainfluenzae sometimes causes pneumonia or bacterial endocarditis. Haemophilus ducreyi causes chancroid. Haemophilus aphrophilus is a member of the normal flora of the mouth and occasionally causes bacterial endocarditis. Haemophilus aegyptius, which causes conjunctivitis and Brazilian purpuric fever, and Haemophilus haemolyticus
Haemophilus influenzae is a small, nonmotile Gram-negative bacterium this bacteria is classified as type-able (encapsulated) and non-type-able (non encapsulated) according to the presence or absence of capsule .Encapsulated strains of Haemophilus influenzae are coccobacilli, similar in morphology to Bordetella pertussis, the agent of whooping cough. ,and are further classified into 6 serotypes(a-f) , with the Haemophilus influenzae serotype b being the most pathogenic for humans, responsible for respiratory infections, ocular infection, sepsis and meningitis. While non encapsulated strains are pleomorphic and often exhibit long threads and filaments. The organism may appear Gram-positive unless the Gram stain procedure is very carefully carried out. Furthermore, elongated forms may exhibit bipolar staining, leading to an erroneous diagnosis of Streptococcus pneumoniae