Growth of Streptococcus faecium in the Presence of Lysozyme

Abstract

Streptococcus faecium can grow normally in the presence of lysozyme, despite the observation that cell suspensions of the organism are lysed readily by the enzyme. Growth in the presence of lysozyme is not due to resistant cells, and the culture is lysed after growth if the p H of the medium is not allowed to drop too low for lysozyme activity. Growth followed by lysis in the presence of lysozyme was not exhibited by other organisms tested which were either significantly more resistant or more sensitive to lysozyme than S. faecium. Lysozyme was active on the cell wall of S. faecium during growth in the presence of 200 μg of the enzyme per ml in a complex medium. It appears that, when actively metabolizing, S. faecium can synthesize the cell wall at a greater rate than lysozyme can hydrolyze it. Thus, the organism is capable of growth in the presence of the enzyme. A large variation in the lytic responses of enterococcal cell suspensions to lysozyme was dependent on the strain used, the growth phase from which the culture was harvested, and the medium in which the culture was grown.