Modification of the Excised Teat Germicidal Activity Assay

The Excised Teat Assay is an in vitro germicidal activity assay for evaluation of bovine teat sanitizers. The rinse procedure of this assay was modified and compared to the standard method. The rinse modification used an ultrasonic cleaner to vibrate the quencher solution to remove bacteria from excised teats after challenge. In alternating trials, bacteria were rinsed from teats by the standard procedure or by the ultrasonic procedure. A 1% iodine based teat sanitizer, a chlorhexidine based teat sanitizer, and a negative control were used in the study. Staphylococcus aureus (ATCC 29740) was used as the challenge organism. No significant differences were obtained by analysis of variance when comparing procedures or in comparing procedures within treatments when an experienced technician conducted the procedure. When an inexperienced technician conducted the procedure, significant differences were obtained between procedures and within treatments when comparing procedures. The modified rinse procedure provided more consistent results than the standard rinse procedure when used by an inexperienced technician.