| Congresso Brasileiro de Microbiologia 2023 | Resumo: 430-2 | ||||
Resumo:Staphylococcus aureus is an important Gram-positive bacteria associated with bovine mastitis, causing both subclinical and clinical manifestation of the disease. This pathogen has capacity of adhesion and biofilm production, which difficult treatment with antimicrobial drugs and, consequently, can lead to chronic infections. In this context, it is mandatory preventing mammary infections by S. aureus in dairy herds and one of the measures adopted is the immersion of the teats in an antiseptic solution both before and after milking, technique known as dipping. Several antiseptic solutions can be used as dipping, however, the frequent use and subinhibitory concentrations can contribute to selective pression and selection of resistant bacterial strains. Thus, this study aimed to assess the susceptibility profile of S. aureus isolated from bovine mastitis to six antiseptics commonly employed as dipping solutions. A total of 400 strains of S. aureus were evaluated, obtained from milk of cows diagnosed with mastitis and obtained between 1994 and 2016. These isolates belong to the Microorganism Collection of the Empresa Brasileira de Pesquisa Agropecuária (Embrapa Gado de Leite). The minimum inhibitory concentration (MIC) for each antiseptic was obtained using the broth microdilution technique, adapted of the protocol proposed by Clinical and Laboratory Standards Institute (CLSI) for antibiotics. Antiseptics and concentrations intervals tested were as follows: hydrogen peroxide (0.002-1.0%), sodium hypochlorite (0.004-2.5%), chlorhexidine gluconate (0.002-1.4%), lactic acid (0.021-10.56%), iodine (0.002-1.0%) and quaternary ammonium (0.004-2.0%). MIC50 and MIC90 were obtained for all antiseptic and the results were, respectively: hydrogen peroxide - 0.002 and 0.004%; sodium hypochlorite - 0.310 and 0.620%; chlorhexidine gluconate - 0.002% (both); lactic acid - 0.082 and 0.165%; iodine - 0.008; and 0.016% and quaternary ammonium - 0.004% (both). Results showed that the higher concentration were needed to inhibit the isolates for sodium hypochlorite (0,62%), although this concentration is compatible with the commonly used as dipping in the field. On the other hand, for the other tested antiseptics, the concentrations required to inhibit S. aureus were much lower than those usually used in dairy farms. However, it is worth highlight that these results were obtained in an in vitro study, with longer exposure time to antiseptics and without the challenges found in the field, which probably reduces the need for an active principle for inhibit the pathogens. In conclusion, the S. aureus strains isolated from bovine mastitis were susceptible to all antiseptics in concentrations usually used as dipping. Palavras-chave: bovine disease, cattle, MIC, minimum inhibitory concentration, resistance Agência de fomento:CAPES, CNPq, FAPEMIG | |||||