Efficacy of photodynamic treatment with new methylene blue on planktonic cells and biofilms of Salmonella isolated from vegetal sources in Brazil

Author(s)

Vilela, Felipe Pinheiro ; Francisco, Camila Guedes ; Brancini, Guilherme Thomaz Pereira ; Rodrigues, Dalia dos Prazeres ; Medeiros, Marta Ines Cazentini ; Braga, Gilberto ubida Leite ; Falcao, Juliana Pfrimer

• Document type: Journal article
• Source: Food Research International; v. 211, p. 9-pg., 2025-04-23.

Abstract

Non-typhoid Salmonella enterica (NTS) serovars Enteritidis (S. Enteritidis), Infantis (S. Infantis), and Typhimurium (S. Typhimurium) are among the main pathogens causing foodborne diseases in humans worldwide. Considering their broad presence in several hosts, including plants, and their increasing antimicrobial resistance rates globally, methods to control spoilage and eradicate these pathogens are necessary. Antimicrobial photo-dynamic treatment (APDT) shows promising results for the control of foodborne pathogens, but only few studies have analyzed the potential of this method to control NTS, especially among isolates from vegetal sources. Therefore, this study evaluated the effect of APDT with new methylene blue N (NMBN) against planktonic cells and biofilms of S. Enteritidis, S. Infantis, and S. Typhimurium isolated from vegetal sources in Brazil. The eight strains were exposed to APDT with 6.25, 12.5, and 25 mu M of NMBN and 4.16, 12.5, and 25 J/cm2 light fluences (5, 15 and 30 min, respectively) for planktonic cells. Two S. Enteritidis and one S. Infantis strains with consistent biofilm formation on crystal-violet staining assay and confocal microscopy were selected for the anti-biofilm APDT under the same conditions. For planktonic cells, 12.5 or 25 mu M NMBN with 15 and 30 min exposures fully eradicated all strains tested. For biofilms, these conditions reduced cell counts for all strains, showing that APDT is effective in controlling biofilms. In conclusion, APDT with NMBN was capable of successfully eradicating planktonic cells of S. Enteritidis, S. Infantis, and S. Typhimurium, and also reduced cell counts of S. Enteritidis and S. Infantis biofilms. These results showed the promising capacity of APDT treatment with NMBN as a method for the control and eradication of NTS in food items. (AU)

• FAPESP's process: 22/07013-0 - Genome analyses, transcriptome, mutants' construction and phenotypic characterization of Campylobacter coli strains isolated from different sources during 25 years in Brazil
• Grantee: Juliana Pfrimer Falcão
• Support Opportunities: Regular Research Grants
• FAPESP's process: 21/07365-0 - Genomic, transcriptomic and phenotypic evaluation of virulence aspects of Salmonella Infantis strains isolated from diverse sources in Brazil
• Grantee: Felipe Pinheiro Vilela
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/11386-5 - Mechanistic study of perception and response to visible light in the entomopathogenic fungus Metarhizium acridum
• Grantee: Gilberto Úbida Leite Braga
• Support Opportunities: Regular Research Grants