Staphylococcus aureus and S. epidermidis are the major teat skin bacteria and lead to\nsevere bovine mastitis. Teat antiseptic is an important tool for controlling intramammary infection.\nThe antibacterial activity of lactic acid (LA) against one reference strain of S. aureus ATCC 25923 and\ntwo field strains including S. aureus and S. epidermidis was investigated using the broth microdilution\nmethod. Its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)\nwere 0.5% for strains belonging to both species. An antiseptic preparation containing 5% LA with\nmodified rice gel (LA-RG) was successfully prepared. Rheological behavior of LA-RG was found to\nbe a pseudoplastic flow with thixotropy with viscosity of approximately 0.007 Pas. LA-RG exhibited\na sufficient adhesive property in the rolling ball test with a length of 9.67 ± 0.04 cm. Killing kinetic\nstudies of LA-RG showed that the killing rate of LA-RG was significantly faster than that of LA.\nAfter 32 min of exposure to LA-RG, approximately 86% and 60% of S. aureus and S. epidermidis were\nreduced, respectively. Abnormal bacterial cell surface after exposure to LA-RG was observed by\nscanning electron microscopy. It is concluded that LA-RG is a promising preparation as an alternative\nproduct for preventing mastitis in dairy cattle
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