The effect of incorporation of cloxacillin in liposomes on treatment of experimental staphylococcal mastitis in mice.

Abstract

The effect of incorporation of cloxacillin in liposomes on the treatment of staphylococcal mastitis was assessed bacteriologically 18 h after treatment of experimental infections in mice caused by two strains of Staphylococcus aureus. Intramammary treatments were cloxacillin incorporated in liposomes, cloxacillin in combination with liposomes, empty liposomes, cloxacillin in saline and saline alone. In none of the experiments did entrapment of cloxacillin within liposomes enhance its antibacterial effects. Electron microscopic studies demonstrated the presence of liposomes in neutrophils which also contained staphylococci. The results support the hypothesis that intracellular staphylococci are metabolically dormant and therefore not susceptible to the action of inhibitors of cell wall synthesis such as cloxacillin.