| Congresso Brasileiro de Microbiologia 2023 | Resumo: 434-2 | ||||
Resumo:Escherichia coli is the major Gram-negative bacteria associated with mastitis worldwide and is known as an opportunistic pathogen that normally causes acute infections with severe clinical signs. Dipping technique consists in teat immersion in an antiseptic solution before (pre-dipping) and after (post-dipping) milking, and is a key measure for mastitis control. Several antiseptics solutions can be used as dipping; however, the frequent use and sub-inhibitory concentrations can contribute to emergence of resistant strains to these antiseptics. Thus, the objective of this study was to assess the susceptibility profile of E. coli isolates from cases of bovine mastitis to various antiseptics commonly used as dipping solutions. A total of 52 strains of E. coli were evaluated, obtained from milk of cows diagnosed with mastitis across different municipalities in the southern region of the state of Minas Gerais, Brazil. These strains belong to the Microorganism Collection of the Laboratórios Integrados de Sanidade Animal e Saúde Coletiva (LISASC) between 2004 and 2016. The broth microdilution technique, adapted from the proposed by the Clinical and Laboratory Standards Institute (CLSI) for antibiotics, was used to assess the Minimum Inhibitory Concentration (MIC) for six antiseptics and the following concentrations: 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 each antiseptic and results were as follows: hydrogen peroxide: 0.002% and 0.004%; sodium hypochlorite: 1.25% for both; chlorhexidine gluconate: 0.002% for both; lactic acid: 0.165% and 0.33%, iodine: 0.016% for both; and quaternary ammonium: 0.016% and 0.031%. The results revealed that the concentration required to inhibit E. coli was highest for sodium hypochlorite (1.25%), being almost double of that recommended by the National Mastitis Council (NMC) (0,64%). This result represents a problem for animal health and mastitis control, since the concentration commonly used is probably not capable of prevent intramammary infections in farms. Still, this find represents a problem for public health, since E. coli is also an important pathogen for human. For the other tested antiseptics, in contrast, inhibition concentrations were much lower than those recommended in the literature and used in field. However, it is important to highlight that this concentration was obtained in an in vitro experiment, carried out with controlled environment and with prolonged exposure time. In this way, more studies are needed to evaluate the ideal concentrations of antiseptics used as dipping. In conclusion, all mastitis-causing E. coli strains were inhibited using low concentrations of the most of tested antiseptics, except for sodium hypochlorite.
Development Agency: CAPES, CNPq, FAPEMIG, UFLA Palavras-chave: antimicrobial resistance, cattle, bovine diseases, minimum inhibitory concentration, MIC Agência de fomento:CAPES,CNPq,FAPEMIG,UFLA | |||||