Prevalence of Biofilm-Forming Non-Typhoidal Salmonella Across the Farm-to-Fork Continuum: A Systematic Review and...

Non-typhoidal Salmonella (NTS) remains a major cause of foodborne illness worldwide, and its persistence along the food-production continuum poses a significant public health challenge. Biofilm formation is an adaptive mechanism that enhances NTS survival and persistence outside the primary animal reservoir, particularly under extra-host stress conditions in food and environmental settings. We hypothesized that true biofilm-positive NTS are less prevalent in animal reservoirs and relatively enriched in food-, environmental-, and human-associated sources along the farm-to-fork continuum, reflecting their increased likelihood of persisting in foods and contributing to human exposure. Systematic review and meta-analysis were conducted following PRISMA guidelines, identifying 88 eligible studies; 57 qualified for systematic review, and 47 and 35 qualified for source- and serogroup-based meta-analyses, respectively. Descriptive synthesis revealed substantial biological and methodological heterogeneity across studies. Proportion-based analysis showed that true biofilm-positive (TBP) prevalence was lowest among animal isolates (58.4%), increased in food (67.7%) and human isolates (73.1%), and was highest among environmental isolates (88.1%) (χ² test, p < 0.001). In the source-based meta-analysis, the pooled TBP prevalence was 73.9% (95% CI: 58.4-85.06%). Meta-regression demonstrated that the predicted proportion of TBP NTS among food and human sources was significantly higher compared with the animal reservoir (food: p = 0.0002; human: p = 0.0005), whereas the difference between the environmental and animal reservoirs was not statistically significant (p = 0.075). These findings suggest that biofilm-forming NTS are enriched outside the primary animal reservoir under extra-host stress conditions. The results raise testable hypotheses regarding biofilm-mediated persistence and enrichment across the food-production continuum and support future longitudinal studies to evaluate its role in transmission and targeted sanitation strategies.