| Summary: | Mastitis is inflammation of mammary glands usually caused by bacteria such as <i>Staphylococcus aureus</i>. Dairy cows are susceptible to mastitis during early dry and transition periods. Effective vaccine is needed during these periods. One of the limitations to develop an effective vaccine against <i>S. aureus</i> is the absence of good infection model. Intramammary infusion (IMIF) with <i>S. aureus</i> has been used as an infection model to test vaccine efficacy. IMIF is reliable in causing mastitis, but it bypasses physical barriers, non-specific natural defenses, and immunity in the teat canal. IMIF also transfers a large number of bacteria into the intramammary area at once. The objective of this study was to develop <i>S. aureus</i> IMIF model that mimics natural infection. Eight Holstein dairy cows were randomly divided into two groups of experimental (<i>n</i> = 5) and control (<i>n</i> = 3) cows. All teats of experimental cows were dipped in <i>S. aureus</i> culture suspension, whereas that of control cows were dipped in phosphate-buffered saline. Results showed that four of five cows were infected with challenge strain by day 3 of the challenge. The remaining cow was infected with <i>Staphylococcus chromogenes.</i> In conclusion, an experimental <i>S. aureus</i> intramammary infection can be induced by teat dipping into bacterial suspension.
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