PSV-16 - Probiotic and synbiotic preparations limit growth of multidrug resistant pathogens in vitro

Abstract: Nutritional supplements promoting animal health and well-being have become prevalent through the increased adoption of prebiotics and/or probiotics. Moreover, recent research has also led to the use of additional biotics such as postbiotics, synbiotics and paraprobiotics which could have a role supporting intestinal function and gut microbiome. With the rise in antimicrobial resistance (AMR) and limitations on the use of antibiotics, greater focus is now on potential novel feed ingredients that combat the prevalence and transmission of AMR. Research has also suggested that postbiotic preparations could be considered as effective alternatives to commercial antibiotics. Therefore, a study was conducted to evaluate the antimicrobial efficacy of probiotic and synbiotic preparations to restrict and inhibit growth of enteric pathogens, including multidrug resistant variants in vitro. These included E.coli ETEC, E.coli 0157:H7 and Salmonella Enteritidis, as well as multidrug-resistant (MDR) Salmonella Dublin, MDR E.coli, and ESBL-producing E.coli isolates from swine. Four synbiotic preparations comprised of Lactobacillus derived probiotics produced under different growth conditions and combined with different yeast mannan rich fractions were cultured overnight in MRS media (0.1%, w/v). Cell-free supernatant (CFS) was collected following overnight incubation at 37°C (4000rpm, 0.22µm filter). Antimicrobial activity was tested by agar-well diffusion method, expressed as zone of inhibition (ZOI), and growth kinetics by broth microdilution overnight using a Varioskan LUX Multimode Microplate Reader (OD @595nm). Statistical analysis was performed using Minitab statistical software (version 20.4). One-way ANOVA with Tukey’s Pairwise comparison was carried out to test for significant differences between means per bacteria species. All synbiotic preparations exhibited inhibitory (P < 0.05) effects against each of the pathogenic bacteria tested. Restriction of bacterial growth was species dependant and significantly reduced by each synbiotic preparation. In terms of growth restriction measured by ZOI analysis, Synbiotic 2, 3, and 4 had higher efficacy (P < 0.05) than Synbiotic 1 in reducing growth of MDR E.coli and MDR Salmonella. Growth analysis with differing synbiotic preparations determined that non-resistant E.coli and Salmonella was reduced by 39 – 90%, whilst growth of the multidrug-resistant variants was reduced by 45 – 96 %, relative to bacteria control (P < 0.05). Reduction in growth of E.coli, Salmonella, and notably drug-resistant species of E.coli and Salmonella was determined (P < 0.05). In conclusion, synbiotic preparations proved an effective alternative to different commercial antibiotics, with broad spectrum antibacterial potential. The use of functional dietary components, such as synbiotics, could represent an innovative approach to combat antimicrobial resistance.