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Neeta Khandekar, Judith Flanagan, Keizo Watanabe, Rani S Bandara, Amali Ariyavidana, Brien A Holden, Eric B Papas, Hua Zhu; GML inhibits lipase production by ocular isolates. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3675.
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Evaporative dry eye is usually linked to an unstable tear film. Alterations in the meibomian lipids can cause evaporation of the tear film and exacerbate dry eye conditions. Lipase produced by commensal ocular bacteria such as Staphylococcus aureus and Staphylococcus epidermidis might play a role in dry eye by degrading meibomian lipids. Glycerol monolaurate (GML) is known to inhibit lipase production by Gram positive bacteria including S. aureus on skin and mucosal surfaces. We studied the effect of GML in inhibiting lipase production by ocular isolates in addition to its effect on bacterial cell growth.
Concentrations of GML from 5 μg/mL - 25 μg/mL were prepared in Tryptic Soy Broth (TSB). Test strains S. aureus 020 & 134, and S. epidermidis 001 & 024 were inoculated at the density of 106 in varying concentrations of GML for 24 h at 37°C with constant shaking. After 24 h, the bacterial suspensions were centrifuged and the supernatant was analyzed for presence of bacterial lipases using commercial Lipase assay kit. Bacterial cell growth was assessed by measuring OD at 660 nm. The test was conducted 3 times.
GML inhibited lipase production by test strains in a dose-dependent manner, with 50% (±25%) inhibition at 10 μg/mL and 88% (±7%) at 17.5 μg/mL for S. aureus 020; and 25% (±21%) at 10 μg/mL and 63% (±9%) at 17.5 μg/mL for S. aureus 134. For S. epidermidis 001 the inhibition was 28% (±14%) at 7.5 μg/mL and 43% (±12%) at 12.5 μg/mL; whilst, for S. epidermidis 024, it was 52% (±7%) at 7.5 μg/mL and 64% (±22%) at 12.5 μg/mL. GML showed significant (p < 0.05) lipase inhibition above concentrations of 15 μg/mL in S. aureus 020 and S. aureus 134, without exhibiting antimicrobial activity for the tested concentrations. For S. epidermidis 001 and S. epidermidis 024, GML showed significant (p < 0.05) lipase inhibition above 10 μg/mL and 7.5 μg/mL, respectively.
GML inhibits lipase production by S. aureus and S. epidermidis at low concentrations without adversely affecting bacterial cell growth. Therefore, GML in low concentrations can be used to inhibit lipases produced by ocular isolates without proving detrimental to commensal bacteria.
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