Inhibition of phage infection in capsule-producing Streptococcus thermophilus using concanavalin A, lysozyme and saccharides

Abstract

Lactic cultures that produce capsular polysaccharides are widely used in the dairy industry. However, little information is available on their phage-cell interactions. Concanavalin A (Con A), lysozyme, and
saccharides were investigated for their ability to modify phage-cell interactions in such a manner as to inhibit phage infection. The ability of phage to infect cells was determined by measuring acid
production in Elliker broth. Acid production by capsule-producing Streptococcus thermophilus was inhibited less by bacteriophage when cells were pretreated with Con. A than was acid production by a
capsule-free variant. The presence of 0.5 mg/ml lysozyme in Elliker broth significantly reduced phage infection. However, there was no increased effect when lysozyme and Con A were combined in the
growth medium. The addition of 5 g/L of glucosamine to Elliker broth also inhibited phage infection. The results of this study indicate that it is possible to reduce phage infection of capsule-forming S.
thermophilus by blocking or modifying phage adsorption sites.