Isolation of spheroplastic forms of Haemophilus influenzae from sputum in conventionally treated chronic bronchial sepsis using selective medium supplemented with N-acetyl-D-glucosamine: possible reservoir for re-emergence of infection.

The isolation rate of Haemophilus influenzae from patients with persistent production of purulent sputum has been increased by the routine use of a selective medium. Nevertheless, some purulent sputum still fails to yield a pathogen. The selective medium was supplemented with N-acetyl-D-glucosamine to encourage primary isolation of colony forming, spheroplastic H influenzae, which reverted to normal forms on subculture. On the basis of in vitro experiments it is postulated that these spheroplastic forms of H influenzae may be induced by inadequate antimicrobial chemotherapy and may be responsible for re-emergence of symptoms in these patients during or shortly after stopping chemotherapy.