Fatty acids and monoacylglycerols inhibit growth of Staphylococcus aureus

Staphylococcus aureus causes a variety of human infections including toxic shock syndrome, osteomyelitis, and mastitis. Mastitis is a common disease in the dairy cow, and S. aureus has been found to be a major infectious organism causing mastitis. The objectives of this research were to determine which FA and esterified forms of FA were inhibitory to growth of S. aureus bacteria. FA as well as their mono-, di-, and triacylglycerol forms were tested for their ability to inhibit a human toxic shock syndrome clinical isolate (MN8) and two S. aureus clinical bovine mastitis isolates (305 and Novel). The seven most potent inhibitors across all strains tested by minimum inhibitory concentration analysis included lauric acid, glycerol monolaurate, capric acid, myristic acid, linoleic acid, cis-9, trans-11 conjugated linoleic acid, and trans-10, cis-12 conjugated linoleic acid. Some of these lipids were chosen for 48-h growth curve analysis with a bovine mastitis S. aureus isolate (Novel) at doses of 0, 20, 50, and 100 μg/mL except myristic acid, which was tested at 0, 50, 100, and 200 μg/mL. The saturated FA (lauric, capric, myristic) and glycerol monolaurate behaved similarly and reduced overall growth. In contrast, the polyunsaturated FA (linoleic and cis-9, trans-11 conjugated linoleic acid) delayed the time to initiation of exponential growth in a dose-dependent fashion. The results suggest that lipids may be important in the control of S. aureus during an infection.