SYNERGIC ANTISTAPHYLOCOCCAL PROPERTIES OF LACTOFERRIN AND LYSOZYME

Staphylococcus epidermidis colonises a wide range of implanted prosthe tic devices, but rarely contact lenses - despite a similarity in mater ial composition. A conceivable explanation for this anomaly is the act ion of the tear defences, including the constitutive proteins lactofer rin and lysozyme. Therefore this study investigated the effect of lact oferrin, lysozyme and serum on the growth of S. epidermidis isolates i n artificial tear fluid. Whether supplemented with serum alone or seru m with either apolactoferrin or lysozyme, this medium induced a simila r, strain-variable effect. However, simultaneous addition of these pro teins induced a greater bactericidal or bacteristatic effect. Of those strains killed by the concerted action of apolactoferrin and lysozyme , the absence of serum led to a further increase in the bactericidal e ffect, whereas strains displaying bacteriostasis were unaffected by se rum. Iron saturation of lactoferrin reversed the antimicrobial synergy of apolactoferrin and lysozyme, These results show synergy between la ctoferrin and lysozyme which is dependent on the iron limitation of la ctoferrin, As a bactericidal mechanism, this synergy is augmented by s erum, but bacteriostasis remains unaffected by serum supplemention, Th us, the combination of lysozyme and lactoferrin may partly explain the low level of contact lens colonisation by S. epidermidis irt vivo.