RESUMO
Biofilms formed on implanted devices are difficult to eradicate. Adhesion mechanism, high bacterial density, aggregation, induction of persisters and stressed bacteria are some of the factors considered when the antimicrobial resistance of these biofilms is analyzed. The aim of this work was to provide an alternative approach to the understanding of this issue by using a specially designed experimental set up that includes the use of microstructured (MS) surfaces (potential inhibitors of bacterial aggregation) in combination with antimicrobial agents (streptomycin and levofloxacin) against Staphylococcusaureus attached cells. Biofilms formed on smooth surfaces were used as plain controls (biofilmed-PC) characterized by the formation of dense 2D bacterial aggregates. Results showed bacterial persistence when streptomycin or levofloxacin were applied to PC-biofilms. The antimicrobial activity of both antibiotics was enhanced when bacteria were attached on MS, where single cells or small aggregates were observed. Thus, dense 2D aggregates of bacteria seem to be crucial as a required previous stage to develop the antimicrobial resistance.
Assuntos
Aderência Bacteriana/efeitos dos fármacos , Biofilmes/crescimento & desenvolvimento , Farmacorresistência Bacteriana/efeitos dos fármacos , Levofloxacino , Staphylococcus aureus/fisiologia , Estreptomicina , Biofilmes/efeitos dos fármacos , Levofloxacino/química , Levofloxacino/farmacologia , Estreptomicina/química , Estreptomicina/farmacologiaRESUMO
The detrimental effects of biofilms are a cause of great concern in medical, industrial and environmental areas. In this study, we proposed a novel eradication strategy consisting of the combined use of micropatterned surfaces and antibiotics on biofilms to reduce the rate of bacterial colonisation. Pseudomonas fluorescens biofilms were used to perform a comparative evaluation of possible strategies to eradicate these biological layers. First, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration of planktonic cultures were determined. Subsequently, adhesion of bacteria on microstructured gold surfaces (MS) with patterned features that were similar to the bacterial diameter as well as on smooth nanostructured gold (NS) was assessed. As expected, lower bacterial attachment as well as inhibition of bacterial aggregation were observed on MS. The effect of streptomycin treatment (ST) in the concentration range 1-4 mg/L (0.25-1× MIC) on biofilms grown on MS and NS was also evaluated. The combined strategy involving the use of micropatterned surfaces and antibiotic treatment (MS+ST) to eradicate Pseudomonas biofilms was then investigated. Results showed a synergistic effect of MS+ST that yielded a reduction of ≥1000-fold in the number of surviving biofilm bacteria with respect to those obtained with single ST or MS. The combined strategy may be a significant contribution to the eradication of biofilms from different environments. In addition, the important role of early monolayer bacterial aggregates in increasing resistance to antimicrobial agents was demonstrated.