Growth-enhancing effect of Branhamella catarrhalis culture filtrates on the L-forms of Haemophilus influenzae.

Abstract

Haemophilus influenzae is a common respiratory pathogen and recurrent infection due to H. influenzae is a phenomenon often present in patients with chronic respiratory tract infections. The effects of Neisseria perflava and B. catarrhalis culture filtrates on the growth and reversion of H. influenzae L-forms were determined using the L-forms of H. influenzae induced and subcultured in a medium containing 10% sucrose and these culture filtrates. When each culture filtrate of two strains of N. perflava was added, the viable count of revertants reached a peak of growth after 48 hr and exceeded 10(4) CFU/ml even 48 days after the subculture. Adding each culture filtrate of six strains of B. catarrhalis, the viable count of revertants from the L-forms of H. influenzae was much higher than that in the absence of any filtrate (negative control). The filtrate of a culture prepared from one of the six strains of B. catarrhalis was subjected to biochemical analysis. The molecular weight of the growth-enhancing factor(s) was determined to be approximately 1,000 to 5,000. Some peptide fractions showed growth-enhancing effects on the L-forms of H. influenzae. These findings suggest that culture filtrates may be important clues as to the correlation between recurrent infections due to H. influenzae and the growth of L-forms in the sputum of the patients with chronic respiratory tract infections, during or after the administration of beta-lactam antibiotics.