PO35 | BACTERIOCINS FOR THE CONTROL OF STAPHYLOCOCCUS AUREUS: META-ANALYSIS, LAB SCREENING, AND PLANTARICIN-BASED STRATEGIES

Cristian Piras¹, Rosario De Fazio¹, Pierluigi Aldo Di Ciccio², Paola Roncada¹ | ¹Department of Health Sciences, University “Magna Græcia” of Catanzaro, Italy; ²Department of Veterinary Sciences, University of Turin, Grugliasco, Torino, Italy.

Food safety remains a major challenge because of the persistence of foodborne pathogens, the spread of antimicrobial resistance, and the need for sustainable alternatives to conventional chemical preservatives. Bacteriocins, particularly those produced by lactic acid bacteria (LAB), are natural antimicrobial peptides with potential applications in controlling pathogenic and spoilage microorganisms in foods of animal origin.
This work integrates systematic evidence assessment with preliminary experimental screening and combination testing. A systematic review and meta-analysis were conducted in PubMed, Scopus, and Web of Science to identify bacteriocins active against bacterial and parasitic hazards relevant to food safety. Studies reporting quantitative minimum inhibitory concentration (MIC) values for purified bacteriocins were included in the antibacterial synthesis, with values standardized to mg/mL and evaluated through family-level random-effects models. Of 5,291 records identified, 5,072 remained after duplicate removal and 46 studies were included. Staphylococcus aureus was associated with the largest number of active bacteriocins, while the evidence base was broader for Gram-positive than for Gram-negative targets. Micrococcins showed the lowest pooled MIC values against Gram-positive bacteria, followed by enterocins and subtilosins. Plantaricins showed intermediate activity against Gram-positive targets and were the only family supported by sufficient independent studies for quantitative aggregation against Gram-negative bacteria.
The potential of plantaricin as part of a combined natural antimicrobial strategy was further investigated against S. aureus. Plantaricin was tested with an essential-oil blend composed of Myrtus communis, Salvia officinalis, and Cistus ladanifer, previously evaluated against a raw-milk Staphylococcus xylosus isolate. The MICs of the essential-oil blend and plantaricin alone were 5.00 and 0.417 mg/mL, respectively. In combination, growth inhibition was obtained with 2.50 mg/mL of the essential-oil blend and 0.104 mg/mL of plantaricin. The resulting fractional inhibitory concentration index was 0.75, indicating an additive interaction. These findings connect literature-based evidence with the identification of antimicrobial LAB and the evaluation of bacteriocin-phytobiotic combinations.
In parallel, two milk-derived LAB isolates, strains 5 and 9, were evaluated against S. aureus. Both produced inhibition in spot assays, with mean inhibition-zone diameters of 6.0 and 9.7 mm, respectively, and their cell-free culture supernatants retained antimicrobial activity. A co-culture challenge model was also established in sterile milk and tryptic soy broth using serial dilutions of strain 9 to assess antagonistic activity under food-relevant conditions.
Plantaricin and bacteriocin-producing LABs, used alone or in combination, may represent useful tools for food biopreservation.