Abstract
The aim of this study is to evaluate the chlorhexidine gluconate (CHG) susceptibility in both planktonic cells and biofilm of 32 Gram-negative (Gn) and 6 Gram-positive (Gp) isolates by minimal inhibitory concentration (2–256 μg/mL for Gn and 2–32 μg/mL for Gp), minimal bactericidal concentration (4–256 μg/mL for Gn and 2–32 μg/mL for Gp) in planktonic cells, and minimal biofilm elimination concentration (128 ≥ 16,384 μg/mL in Gn and 32 ≥ 16,384 μg/mL in Gp) in biofilm environment. Our study showed that Gn isolates have higher minimal concentrations than Gp and bacteria in biofilms are more tolerant than planktonic ones. No correlation between MBC or MBEC and biofilm formation was statistically confirmed. The Eagle effect, previously described for antimicrobials and antifungals, was evidenced in this work for CHG, an antiseptic. Besides that, the phenomenon was described in 23/38 isolates (60.5%), raising minimal concentration up to ≥ 16,384 μg/mL. Our study showed that clinical isolates have a high ability to form biofilm allowing them to tolerate CHG concentrations as high as the ones used in clinical practice. Therefore, attention should be given to the occurrence of this phenomenon to avoid false susceptibility results.
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This study was supported by CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) with a PhD scholarship.
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Study design: S. F. C. and L. V. P. N.; material preparation, data collection, and methodology: A. P. M. and S. V. N.; data analysis: A. P. M., M. F. C., and L. V. P. N.; manuscript review: A. P. M., M. F. C., S. V. N., F. R., A. S. L., S. F. C., L. V. P. N.; funding acquisition: S. F. C. and A. S. L. The first draft of the manuscript was written by A. P. M., and all authors read and approved the final manuscript.
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Ethics approval for this study was obtained through of Ethical Committee of Hospital da Clinicas (São Paulo, Brazil) under the number: 214/19.
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Marchi, A.P., Farrel Côrtes, M., Vásconez Noguera, S. et al. Chlorhexidine susceptibility and Eagle effect in planktonic cells and biofilm of nosocomial isolates. Eur J Clin Microbiol Infect Dis 42, 787–792 (2023). https://doi.org/10.1007/s10096-023-04594-w
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DOI: https://doi.org/10.1007/s10096-023-04594-w