Study objective was to determine efficacy of a novel antimicrobial solution containing citrate ion, methylene blue, parabens and emollients (ZuraLac^SD, Zurex PharmAgra) used as a post-milking teat dip against a positive and negative control in reducing the incidence of new quarter intramammary infections (QIMI) during a period of experimental exposure of teats to contagious mastitis organisms, Streptococcus agalactiae and Staphylococcus aureus. 120 Holstein cows were used in an 8-wk trial with 40 cows/ treatment. Cows were 66–122 DIM and free of IMI. Three treatments were experimental dip - ZuraLac^SD containing 10.0% trisodium citrate with 5.0% emollients used as a post-milking teat dip; positive control – Theratec^R (GEA Farm Technologies Inc.) containing 0.5% iodine with a 3% triple emollient system used as a post-milking teat dip; and a negative control where no post-milking teat dipping occurred. All teats were dipped immediately after machine removal at morning milking with broth suspensions of Streptococcus agalactiae (ATCC 55194) and Staphylococcus aureus (ATCC 12600). Teats were post dipped with appropriate teat dip between 2 and 5 min after teats dipped with culture broth. Duplicate quarter samples were taken aseptically weekly (and when clinical mastitis occurred) to determine quarter bacteriological status (3rd sample when results differed). Infection data were analyzed using Student t-statistics based on percent eligible quarters becoming infected with respective mastitis pathogens. Novel germicide post milking teat dip (3.3% quarter IMI) significantly (P < 0.01%) reduced the number of new infections of Streptococcus agalactiae and Staphylococcus aureus compared with both the negative control (53.7% QIMI; 95.3% reduction) and positive control (13.1% QIMI; 80.9% reduction). Incidence of clinical mastitis with a bacteriological positive identification of one of the challenge organisms was 40, 4, and 0 for negative control, positive control and novel germicide dips, respectively. Novel germicide dip was significantly better than positive and negative controls.