Antibacterial activity of glycerol monolaurate formulated in petrolatum

Glycerol monolaurate (GML) is a fatty acid monoester of glycerol that is approved by the FDA as a food additive and component of cosmetics. We previously showed that 50,000 µg/mL of GML solubilized in the non-aqueous K-Y Warming Gel is broadly antibacterial, including S. aureus and various streptococcal species, and selectively increases beneficial lactobacilli. GML is also anti-inflammatory, reducing harmful inflammation. In the current study, we examined GML and longer or shorter fatty acid monoesters for their anti-staphylococcal activity. GML had the greatest anti-staphylococcal activity. We then showed in vitro that GML solubilized in petrolatum, a non-aqueous gel that has fewer unwanted side effects than K-Y Warming Gel, had enhanced activity in the killing of both methicillin-sensitive and methicillin-resistant S. aureus. GML in petrolatum also killed two coagulase-negative staphylococci. Collectively, all staphylococci were killed by GML concentrations of ≥500 µg/mL. This concentration is 100 times below the concentration of GML we previously used in vivo in humans as solubilized in K-Y Warming Gel. GML in petrolatum also effectively killed four viridans streptococci, organisms increasingly recognized as pathogenic in atopic dermatitis in children. GML (50,000 µg/mL) in petrolatum was bactericidal for S. aureus as tested in a dermatitis model in rabbits. The data suggest that GML in petrolatum, upon additional testing, may become useful in topical management of nasal and skin colonization of children, as well as older individuals, with S. aureus and viridans streptococci, and for use in management of Gram-positive bacteria in atopic dermatitis and diabetic ulcers.IMPORTANCEMost staphylococcal and streptococcal infections in humans originate from mucous membranes, usually the anterior nares, or from the skin. Glycerol monolaurate (GML) solubilized in petrolatum exhibited potent anti-Gram-positive bacteria activity as tested both in vitro and in a staphylococcal rabbit skin model. Because GML is generally recognized as safe (GRAS by FDA) and petrolatum is already approved for topical human use, our data suggest that upon additional testing GML in petrolatum may be effective for topical use in management of nasal and skin colonization with S. aureus and viridans streptococci in young children (as well as older individuals), and for use in management of bacterial infections in atopic dermatitis and diabetic ulcers.