Dados do Trabalho

Título

Activity of cell-free supernatant of Bacillus subtilis strain 118 against pathogenic bacteria

Introdução

Introduction: Probiotics are microorganisms that, when administered via the diet, interact with the microbiota and host cells, promoting health benefits, especially through immunomodulatory activities. During its production, a byproduct called cell-free supernatant (CFS) is generated, containing metabolites and cellular components. CFS has advantages such as greater security, ease of production and multiple mechanisms of action. Bacillus subtilis stands out for producing antimicrobial compounds that are effective against various bacteria, protozoa and fungi. Therefore, it is necessary to verify the activity of CFS derived from B. subtilis strains against pathogenic microorganisms.

Objetivo (s)

Objective: To evaluate the action of CFS from B. subtilis strain 118 against pathogenic microorganisms.

Material e Métodos

Methods: B. subtilis strain 118 was cultivated in Luria Bertani (LB) medium at 37°C for 24 hours with shaking at 180 rpm. The number of bacterial cells was adjusted to the tube equivalent of 0.5 on the McFarland scale and incubated again for 24 hours at 37°C and 180 rpm. CFS was obtained by centrifugation at 12,000g for 15 minutes, neutralized with HCl until pH 6.5 and filtered (0.22 µm). The inhibitory capacity of CFS was tested against Staphylococcus aureus, a resistant strain of bacteria (MRSA), and Escherichia coli. Mueller Hinton agar plates were inoculated with the bacterial suspension. 8 mm wells were drilled and filled with 40 μl of sterile CFS. The plates were incubated at 37°C for 24h and checked for the zone of inhibition. Furthermore, the broth microdilution method was performed in 96-well plates, incubating standardized suspensions of S. aureus, MRSA and E. coli with serial dilutions of CFS (1:2 to 1:512) at 37°C for 18 hours, measuring the absorbance at 470 nm. There was no need to submit to the ethics committee.

Resultados e Conclusão

Results: CFS derived from B. subtilis strain 118 showed efficacy against S. aureus and MRSA, suggesting better activity against Gram-positive bacteria. The significant inhibitory action was evidenced by the formation of an inhibition halo around the wells and by the results of the microdilution method, showing inhibition of bacterial growth at the 1:2 dilution. Conclusion: The findings highlight the potential of CFS obtained from the cultivation of B. subtilis as a promising alternative in combating pathogenic microorganisms, emphasizing the importance of future investigations to explore its therapeutic use and its role in promoting health.

Palavras Chave

Keywords: Probiotic; Bacillus sp.; Gram-positive bacteria; Gram-Negative Bacteria.