Purpose: Determine the efficacy of commercial natural antimicrobial formulations to control growth, biofilm production and swarming of Salmonella.
Methods: Different commercial formulations based on citric extracts were evaluated (Citric AB liquid, Citrik AB powder, Citrol K Ultra, Citrodex, Citrik Max and Citrik Agro). Minimal bactericidal concentrations (MBC) were evaluated against S. monophasic, S. Typhi, S. Typhimurium, S. Muenchen and Salmonella spp. by microplate-dilution method. For swarm motility test, sub-inhibitory concentrations of formulations were mixed with LB with 0.5% agar. Five µl of bacteria cultures were placed in the center of the plate and incubated for 18 h. The extent of swarming motility was determined by measuring the diameter of migration and compared with control. Biofilm formation in polyestirene microtiter plates with TSB was quantified after staining with safranin at OD 492 nm in a microplate reader.
Results: MBC of formulations ranged from 81 to 922 mg/ml. Citrik AB was the most effective in inhibiting Salmonella growth (MBC 81-105 mg/ml). Citrodex showed the highest MBC (900 mg/ml). Most formulations inhibited biofilm formation at 75% of MBC, and a reduction was observed at lower concentrations. However, Citrik AB inhibited the biofilm formation even at 25% of the MBC, and also produced the higher swarming reduction (75%) when 75% of the MBC was added to treatments. The other compounds showed less swarming reduction.
Significance: These formulations could represent good alternatives to control the presence of Salmonella in circumstances were growth, biofilm formation and swarming are involved in survival or contamination.