Haemophilus parainfluenzae is a species of Haemophilus. It is one of the HACEK organisms.H. parainfluenzae is an opportunistic pathogen that has been associated with endocarditis, bronchitis, otitis, conjunctivitis, pneumonia, abscesses and genital tract infections. H. parainfluenzae biotypes I and II are capable of natural genetic transformation. Natural genetic transformation is a bacterial adaptation for DNA transfer. In order for a bacterium to bind, take up and recombine exogenous DNA into its genome it must enter a special physiological state termed natural competence. In H. parainfluenzae, competence is induced during the late stationary phase of growth. Natural DNA transformation may play a major role in the exchange of genetic information among H. parainfluenzae isolates.