Evaluating the effectiveness of commercial teat disinfectant products sold in Ireland using the disc diffusion method

Evaluation of teat disinfectant products for their effectiveness against the most prevalent mastitis-causing bacteria is important to identify the most effective ingredients against specific bacterial strains. Ninety-six commercially available teat disinfectant products were tested against three bacterial strains associated with mastitis in Ireland (Staphylococcus aureus, Streptococcus uberis and Escherichia coli) using the disc diffusion method. Products were reclassified by active ingredients (n = 9) for analysis. These ingredient groups included: chlorhexidine (n = 25), chlorine dioxide (n = 5), diamine (n = 1), iodine (n = 13), iodine combined with lactic acid (n = 5), lactic acid (n = 15), lactic acid combined with chlorhexidine (n = 21), lactic acid combined with hydrogen peroxide (n = 1) and lactic acid combined with salicylic acid (n = 10). The ingredient group chlorine dioxide resulted in the greatest zones of inhibition for all three bacterial strains. An individual product containing a combination of lactic acid and hydrogen peroxide resulted in the greatest zone of inhibition for Sta. aureus and Str. uberis, whereas a specific product within the chlorine dioxide group resulted in the greatest zones of inhibition for E. coli. High concentrations of active ingredient did not necessarily increase the effectiveness for the majority of teat disinfectant products. It is possible to use the disc diffusion method to evaluate/screen a large number of teat disinfectant products prior to conducting field trials to establish the products’ ability to reduce intramammary infections (IMI).