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Biomédica
Print version ISSN 0120-4157On-line version ISSN 2590-7379
Abstract
MORENO, Xiomara; VENTURA, Melanie; PANIZO, María Mercedes and GARCES, María Fátima. Assessment of biofilms formation of bacterial and fungal isolates using qualitative Congo red agar and semiquantitative crystal violet microtiter methods. Biomed. [online]. 2023, vol.43, suppl.1, pp.77-88. Epub Aug 31, 2023. ISSN 0120-4157. https://doi.org/10.7705/biomedica.6732.
Introduction.
Sixty-five percent of human infections are caused by bacteria or yeasts able to form biofilms. This feature makes them more resistant to antimicrobials and antifungals.
Objective.
To determine biofilm formation capacity of bacterial and fungal isolates by quantitative crystal violet microtiter and qualitative Congo red agar methods.
Materials and methods.
Brain-heart infusion, trypticase soy broth and Müeller-Hinton culture media were used in bacterial isolates for the quantitative method; brain-heart infusion broth and Sabouraud dextrose were used for yeasts. The same culture media plus 3% Congo red and 10% dextrose were used to apply the qualitative method in agar. The proposal by Stepanovic, et al. was used as a reference method.
Results.
We evaluated 103 bacterial isolates and 108 yeasts isolates. We did not recommend substitute brain-heart infusion broth for trypticase soy and Müeller-Hinton broths for biofilm formation assessment in bacterial isolates using the quantitative method. Sabouraud dextrose medium, both broth and agar, can replace brain-heart infusion to assess biofilm formation in yeasts, quantitatively and qualitatively.
Conclusion.
The study of biofilms in the microbiology laboratory, using Congo red agar qualitative method, is a simple, fast, and inexpensive procedure that provides precise information for the diagnosis and treatment of persistent infections caused by bacteria and yeasts.
Keywords : Biofilms; Gram-positive bacteria; Gram-negative bacteria; yeasts; Congo red.