Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology] · 2026
Multi-strain probiotic suppression of Staphylococcus aureus virulence: Growth kinetics, enterotoxin production, and sea/seb gene expression under Lactobacillus casei, Lactobacillus plantarum, Bifidobacterium bifidum and consortia co-culture conditions.
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Parihar Himani, Chaturvedi Priyanka, Dayal Ranu, Tirumalai Prem Saran
Аннотация
BACKGROUND: Staphylococcus aureus causes staphylococcal food poisoning (SFP), mediated through heat-stable enterotoxins encoded by virulence genes sea and seb. Probiotic biocontrol represents a promising upstream intervention, yet simultaneous mechanistic evidence spanning growth inhibition, toxin suppression, and virulence gene transcriptional downregulation remains limited.
OBJECTIVES: To evaluate the capacity of Lacticaseibacillus casei (formerly Lactobacillus casei), Lactiplantibacillus plantarum (formerly Lactobacillus plantarum), Bifidobacterium bifidum, and their defined consortia to suppress S. aureus across three analytical tiers: growth kinetics, enterotoxin production (ELISA), and sea/seb gene expression (RT-qPCR).
METHODS: Probiotic-pathogen co-cultures were established in broth and sampled at 24, 48, and 72 h. Viable counts were determined by standard plate count (Log₁₀ CFU/mL, verified by standard plate count). Enterotoxin levels were quantified by ELISA. Relative expression of sea and seb was determined by RT-qPCR using the 2⁻ᴵᴵᴺᵗ method with dual housekeeping gene normalisation (gmk and tpi).
RESULTS: All treatments reduced S. aureus viability and enterotoxin production vs. controls. The consortium was bactericidal (µ = -0.178 h⁻¹), achieving a 4.56 log₁₀ CFU/mL reduction and 58.1% enterotoxin suppression at 72 h (p < 0.01). sea was downregulated across all treatments (FC 0.0002-0.67 at 24 h). seb showed stationary-phase upregulation in individual strain treatments at 48 h, while the consortia sustained transcriptional downregulation of both genes throughout (sea: 0.0002-0.044; seb: 0.0014-0.009).
CONCLUSION: Three-tier evidence confirms that the consortia coherently suppresses S. aureus growth, enterotoxin accumulation, and virulence gene transcription. The seb stationary-phase transcriptional downregulation These results support multi-strain probiotic formulations as biocontrol agents in food safety applications.
OBJECTIVES: To evaluate the capacity of Lacticaseibacillus casei (formerly Lactobacillus casei), Lactiplantibacillus plantarum (formerly Lactobacillus plantarum), Bifidobacterium bifidum, and their defined consortia to suppress S. aureus across three analytical tiers: growth kinetics, enterotoxin production (ELISA), and sea/seb gene expression (RT-qPCR).
METHODS: Probiotic-pathogen co-cultures were established in broth and sampled at 24, 48, and 72 h. Viable counts were determined by standard plate count (Log₁₀ CFU/mL, verified by standard plate count). Enterotoxin levels were quantified by ELISA. Relative expression of sea and seb was determined by RT-qPCR using the 2⁻ᴵᴵᴺᵗ method with dual housekeeping gene normalisation (gmk and tpi).
RESULTS: All treatments reduced S. aureus viability and enterotoxin production vs. controls. The consortium was bactericidal (µ = -0.178 h⁻¹), achieving a 4.56 log₁₀ CFU/mL reduction and 58.1% enterotoxin suppression at 72 h (p < 0.01). sea was downregulated across all treatments (FC 0.0002-0.67 at 24 h). seb showed stationary-phase upregulation in individual strain treatments at 48 h, while the consortia sustained transcriptional downregulation of both genes throughout (sea: 0.0002-0.044; seb: 0.0014-0.009).
CONCLUSION: Three-tier evidence confirms that the consortia coherently suppresses S. aureus growth, enterotoxin accumulation, and virulence gene transcription. The seb stationary-phase transcriptional downregulation These results support multi-strain probiotic formulations as biocontrol agents in food safety applications.