Colonization of the Bovine Teat Duct Following Inoculation with Staphylococcus Aureus and Escherichia Coli

Abstract

The ability of Staphylococcus aureus and Escherichia coli to colonize the bovine teat duct was examined in a series of experiments in which varying numbers of the organisms were inoculated either at the teat orifice or 2 mm into the teat duct. Inoculation with 20 cfu of Staph. aureus failed to produce colonization but placing 200 or 2000 cfu either at the orifice or 2 mm into the duct produced colonization in 60 to 72% and 92% of teats respectively. The number of Staph. aureus recoverable from the teat apex of quarters increased steadily with time and was still rising after 19 days. Intramammary infection was an infrequent consequence of colonization in these short duration experiments, only four infections resulting from a total of 78 colonizations. Contrastingly, inoculation of the duct with up to 43 × 106 cfu of E. coli resulted in only a transient colonization which seldom persisted for more than three or four days. The significance of these observations is discussed in relation to the pathogenesis of udder disease due to E. coli and Staph. aureus.