Atividade antimicrobiana do complexo de rutênio [Ru(phen)2(bpy-ant)]2+ contra bactérias envolvidas em infecções relacionadas à assistência à saúde

Abstract

Healthcare-associated infections (HAI) have become a serious problem in recent years due to the high morbidity and mortality attributed to them, and an aggravating factor is the increasing antimicrobial resistance of microorganisms that are associated with those infections. Given this scenario, ruthenium complexes, whose antimicrobial activity has already been reported in the literature, become an alternative to current drugs. The present study aimed to evaluate the antimicrobial and antibiofilm activity of the [Ru(phen)2(bpy-ant)]2+ complex against the clinically important bacteria Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 700698 (MRSA), Staphylococcus epidermidis ATCC 12228, Staphylococcus epidermidis ATCC 35984 and Escherichia coli ATCC 11303. To evaluate the antimicrobial activity, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were analyzed, while the antibiofilm activity was tested using the crystal violet (CV) staining method of the biomass for quantification and the enumeration of viable cells method by counting colony forming units (CFU). The tests were performed in microtiter plates at concentrations ranging from 1.9 μg/mL to 125 μg/mL. Both MIC and MBC results ranged from 7.8 to 125 µg/mL. S. epidermidis ATCC 12228 had the lowest values ​​of MIC and MBC among all strains, followed by S. aureus ATCC 25923, S. aureus ATCC 700698 and S. epidermidis ATCC 35984, and these last two presented the same value of MBC. E. coli ATCC 11303 presented MIC value equal to S. aureus ATCC 25923 and did not present MBC value. In the quantification of biomass, the Gram-positive bacteria S. aureus and S. epidermidis obtained higher values of percentage of biomass reduction (77 to 100%) when compared to the Gram-negative bacteria E. coli (21 to 67%). In the enumeration of viable cells, S. aureus ATCC 25923 and S. epidermidis ATCC 12228 presented a higher reduction in the number of viable cells when compared to S. aureus ATCC 700698 and S. epidermidis ATCC 35984, which presented higher values ​​than E. coli ATCC 11303. In addition to concentrations in which there was no reduction in the number of viable cells, the values of reduction ranged from 0.2 to 7.71 logs, including the highest concentrations in which there was no growth of CFUs. Therefore, the potential of the ruthenium complex to control microbial growth and to inhibit the growth of biofilms was proven.