In vitro evaluation of the efficacy of commercial disinfectants used in pre and post-dipping against Staphylococcus spp. isolated from bovine mastitis

The objective of this investigation was to evaluate the in vitro sensibility of Staphylococcus spp. to several commercially available disinfectants used for pre and post dipping. A total of 60 isolates of Staphylococcus spp., identified as Staphylococcus aureus (50) and Positive coagulase Staphylococcus (10) were obtained from the mammary glands of dairy cows with subclinical mastitis in the regions of Metropolitan Recife, the Agreste and the Zona da Mata of the State of Pernambuco, Brazil. As active ingredients were used a chlorine base (25%), iodine (0.6%), chlorhexidine (2.0%), quaternary ammonium (4.0%), and lactic acid (2.0%) at four specific intervals (15", 30", 60", and 300"). One hundred percent of S. aureus was found to be sensitive to iodine, 93.3% to chlorhexidine, 80% to ammonia, 35.6% to lactic acid, and 97.8% were resistant to chlorine at a 60-minute interval. With respect to the Positive coagulase Staphylococcus (SCP), 100.0% of the isolates were sensitive to iodine, 81.8% to quaternary ammonium, 99.9% to lactic acid, 72.7% to chlorhexidine, and 100% was resistant to chlorine at an interval of 60 minutes. It can be concluded that the highest disinfectant activity in vitro was found to be with iodine and chlorhexidine for S. aureus, and with iodine and lactic acid for SCP. A further conclusion was that it is important to undertake a periodic evaluation of the disinfectants used on the dairy properties in the regions studied, given the variety of sensibilities and resistance to disinfectants used, which may prejudice the control of bovine mastitis caused by Staphylococcus spp.