Glycerol Monolaurate Inhibits Lipase Production by Clinical Ocular Isolates Without Affecting Bacterial Cell Viability

PURPOSE. We sought to determine the relative lipase production of a range of ocular bacterial isolates and to assess the efficacy of glycerol monolaurate (GML) in inhibiting this lipase production in high lipase-producing bacteria without affecting bacterial cell growth. METHODS. Staphylococcus aureus, Staphylococcus epidermidis, Propionibacterium acnes, and Corynebacterium spp. were inoculated at a density of 10(6)/mL in varying concentrations of GML up to 25 mu g/mL for 24 hours at 37 degrees C with constant shaking. Bacterial suspensions were centrifuged, bacterial cell density was determined, and production of bacterial lipase was quantified using a commercial lipase assay kit. RESULTS. Staphylococcus spp. produced high levels of lipase activity compared with P. acnes and Corynebacterium spp. GML inhibited lipase production by Staphylococcal spp. in a dose-dependent manner, with S. epidermidis lipase production consistently more sensitive to GML than S. aureus. Glycerol monolaurate showed significant (P < 0.05) lipase inhibition above concentrations of 15 mu g/mL in S. aureus and was not cytotoxic up to 25 mu g/mL. For S. epidermidis, GML showed significant (P < 0.05) lipase inhibition above 7.5 mu g/mL. CONCLUSIONS. Lipase activity varied between species and between strains. Staphylococcal spp. produced higher lipase activity compared with P. acnes and Corynebacterium spp. Glycerol monolaurate inhibited lipase production by S. aureus and S. epidermidis at concentrations that did not adversely affect bacterial cell growth. GML can be used to inhibit ocular bacterial lipase production without proving detrimental to commensal bacteria viability.