Haemophilus

Genus of tiny rod-shaped bacteria.

All are strict parasites occurring in the respiratory tracts of warm-blooded animals, including humans, and in certain cold-blooded animals. Some require oxygen, others do not. H. influenzae causes severe bacterial diseases in young children, including meningitis, otitis, and pneumonia. Another species of Haemophilus causes a sexually transmitted disease in humans known as chancroid, or soft chancre. Yet another causes secondary infection in persons with influenza.

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▪ bacteria genus

also spelled  Hemophilus,  

 genus of very small rod-shaped bacteria of uncertain affiliation. All species of Haemophilus are strict parasites occurring in the respiratory tracts of warm-blooded animals, including humans, and in certain cold-blooded animals. All Haemophilus are gram-negative, aerobic or facultative anaerobic and nonmotile and require a growth factor that is found in blood. They are minute in size, H. influenzae measuring 0.3 micrometre across and up to 2 micrometres long.

      H. gallinarum causes infectious coryza in fowl. H. parasuis (itself not disease-causing), together with a virus (Tarpeia suis), causes swine influenza. H. ducreyi causes a venereal disease in humans known as chancroid, or soft chancre. H. influenzae was at one time thought to cause human influenza, but it is now believed to be a source of secondary infection in persons suffering from influenza, which is now known to be a viral disease.

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