Evaluation of Cecropin in circulating strains of Acinetobacter baumannii in the state of Rio de Janeiro

Introduction:Acinetobacter baumannii is a Gram-negative and multidrug-resistant, considered one of the main causes of Healthcare-Associated Infections. A. baumannii has acquired resistance to several antimicrobials.With the increase in bacterial resistance due to the excessive use of antibiotics.Studies indicate that antimicrobial peptides (PAMs) have the potential to inhibit biofilm formation, emerging as a promising therapeutic strategy and, in the literature, cecropin stands out for its broad spectrum of antimicrobial activity.Objectives: This study aims to evaluate the effects of Cecropin in strains of A. baumannii circulating in the state of Rio de Janeiro in order to develop therapeutic inputs.Methodology: Bacterial strains: Three strains of A. baumannii of clinical origin will be studied, in addition to the reference strain A. baumannii ATCC 19606.These strains are part of the Collection of Reference Microorganisms in Health Surveillance of the National Institute for Quality Control in Health of the Oswaldo Cruz Foundation.Determination of minimum inhibitory concentration: will be established from serial dilutions of the antimicrobial peptides in Luria Bertani broth; Bacterial membrane permeability assessment: The bacterial membrane permeability test will be performed by adding propidium iodide; Evaluation of inhibitory of biofilm formation: The inhibition of biofilm formation after treatment with PAMs will be quantified using the crystal violet colorimetric method.Results: MIC: A peptide concentration of 8 g/ml was found to inhibit the growth of all tested strains, marking the MIC for the peptide.Biofilm Formation Inhibition: After confirming the MIC (8 g), we evaluated biofilm formation from the sub-mic (4 g).Statistical analysis performed by GraphPad Prism (version 9.3.0), it was possible to observe that there was no significant difference (P>0.99) between treatments.Membrane Permeability: The membrane permeability test revealed visual differences in the ATCC strain after peptide exposure, with a decrease in cell concentration.In the Gen A strain, a notable difference was observed after 24h of biofilm growth.No significant biofilm damage was observed in the Gen C strain, suggesting potential resistance mechanisms activated by the peptide. Conclusion:Although cecropin is recognized in the literature for its antimicrobial effects, its impact on biofilm formation in contact with the strains circulating in the state of Rio de Janeiro was not shown to be effective.It is noted that the ability of some strains to develop resistance highlights challenges in the therapeutic use of this peptide.