Characterization of genes conferring V factor independence in haemophilus parainfluenzae and haemophilus ducreyi.

Abstract

Haemophilus influenzae and Haemophilus parainfluenzae are obligate human parasites that form part of the flora of the mucous membranes. They are normally present in the mouth and upper respiratory tract of healthy individuals. H. influenzae is known as a major pathogen in children while H. parainfluenzae is an opportunistic pathogen which is also found in the urogenital tract. H. ducreyi, however; has only been isolated from genital ulcers in patients suffering from chancroid. The various species of the genus Haemophilus are characterised by their requirements for two growth factors, X factor or haemin and V factor or nicotinamide adenine dinucleotide (NAD). According to present taxonomic criteria and laboratory practice, isolates belonging to the genus Haemophilus that grow in the absence of NAD cannot be identified as H. influenzae or H. poraintluenzae. However, in 1989 four unusual clinical strains of H. parainfluenzae were isolated which were found to be V factor-independent. (Abbreviation abstract)