Rifaximin is a semi-synthetic rifamycin antibiotic produced by Amycolatopsis mediterranei. It is non-absorbable and acts locally in the gut due to its unique chemical properties. Rifaximin has broad-spectrum activity against gram-positive and gram-negative bacteria as well as protozoa through inhibition of bacterial RNA polymerase. Its localized activity and lack of systemic absorption helps preserve other antibiotics and limits development of resistance. Rifaximin also has anti-inflammatory properties through activation of the pregnane X receptor, reducing levels of pro-inflammatory cytokines. Fatroximin dry cow is a rifaximin formulation developed for intramammary administration as dry cow therapy to