Efficacy of citrus-based disinfectants to inhibit growth, swarming, and biofilm formation of Salmonella and decontaminate parsley

Biofilms allow bacteria to adhere to biological or nonbiological surfaces and are difficult to remove, whereas swarming enables the rapid colonization of nutrient-rich environments. In this study, the efficacy of six commercial citric-based antimicrobial formulations to control growth, biofilm production, and swarming of Salmonella was determined. Furthermore, the efficacy of Citrik Agro® to disinfect contaminated parsley was established. Minimum bactericidal concentrations (MBCs) of the disinfectants against five Salmonella strains were evaluated by the microplate-dilution method. For the swarm motility test, subinhibitory concentrations of the disinfectants were mixed with Luria–Bertani agar. Biofilm formation was quantified in microplates with broth after staining with safranin. Parsley was artificially contaminated with Salmonella, then washed with Citrik Agro and the presence of Salmonella was determined after several days. The MBCs of the disinfectants ranged from 81 to 922 µg/ml. Citrik AB was the most effective inhibitor of Salmonella growth (MBC: 81–105 µg/ml). Most disinfectants inhibited biofilm formation at 75% of the MBC, and a reduction was observed at lower concentrations. However, Citrik AB inhibited biofilm formation even at 25% of the MBC, and it also produced a higher (P<0.05) swarming reduction (75%) when 75% of the MBC was used, compared to the other disinfectants. In addition, Citrik Agro reduced more than 2 logs of Salmonella in parsley. This reduction was higher (P<0.05) than that observed by the chlorine treatment. In conclusion, citric extract-based products could be a natural alternative to reduce the risk of Salmonella contamination in fresh produce.