Haemophilus influenzae

Haemophilus influenzae
H. influenzae on a chocolate agar plate
Scientific classification
Domain:	Bacteria
Phylum:	Pseudomonadota
Class:	Gammaproteobacteria
Order:	Pasteurellales
Family:	Pasteurellaceae
Genus:	Haemophilus
Species:	H. influenzae
Binomial name
Haemophilus influenzae (Lehmann & Neumann 1896) Winslow et al. 1917

Haemophilus influenzae (formerly called Pfeiffer's bacillus or Bacillus influenzae) is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria are mesophilic and grow best at temperatures between 35 and 37 °C.^[1]

H. influenzae was first described in 1893^[2][3] by Richard Pfeiffer during an influenza pandemic^[4] when he incorrectly identified it as the causative microbe, which is why the bacteria was given the name "influenzae".^[5][6] H. influenzae is responsible for a wide range of localized and invasive infections, typically in infants and children,^[7] including pneumonia, meningitis, or bloodstream infections.^[8] Treatment consists of antibiotics; however, H. influenzae is often resistant to the penicillin family, but amoxicillin/clavulanic acid can be used in mild cases.^[9] Serotype B H. influenzae have been a major cause of meningitis in infants and small children, frequently causing deafness and mental retardation. However the development in the 1980s of a vaccine effective in this age group (the Hib vaccine) has almost eliminated this in developed countries.

This species was the first organism to have its entire genome sequenced.^[10][11]