Combined effect of metabolites produced by a modified Lactobacillus casei and berry phenolic extract on Campylobacter and microbiome in chicken cecum contents.

Campylobacter is one of the most common foodborne bacterial pathogens causing illness, known as campylobacteriosis, in the United States. More than 70% of the campylobacteriosis cases have direct or indirect relation with poultry/poultry products. Currently, both conventional and organic/pasture poultry farmers are searching for sustainable alternative to antibiotics which can reduce colonization and cross-contamination of poultry products with Campylobacter and promote poultry health and growth. Probiotic and their nutritional supplement, known as prebiotic, have become consumers' preferences as alternatives to antibiotics/chemicals. In this study, we evaluated the combined effect of plant-derived prebiotic and probiotic-derived metabolites in reducing growth of Campylobacter in cecum contents, a simulated chicken gut condition. Cecum contents were collected from chickens pre-inoculated with kanamycin-resistant Campylobacter (CJRMKm), were incubated over 48 h time period, while being supplemented with either berry phenolic extract (BPE), cell free cultural supernatant from an engineered probiotic, Lactobacillus casei, or their combination. It was found that combine treatments were able to reduce both inoculated and naturally colonized Campylobacter more effectively. Microbiome analysis using 16S rRNA sequencing also revealed that combine treatments were capable to alter natural microflora positively within chicken cecum contents. Differences were observed in bacterial abundance at both phylum and genus level but did not show significant alteration in alpha diversity due to this treatment. PRACTICAL APPLICATION: The results of this study provide critical information for understanding the potential of synbiotic as an alternative in sustainable poultry farming. The outcomes of this study will lead future direction of using combination of probiotic-derived metabolites and BPE in poultry farming.

Antimicrobial and Antivirulence Impacts of Phenolics on Salmonella Enterica Serovar Typhimurium.

Salmonella enterica serovar Typhimurium (ST) remains a major infectious agent in the USA, with an increasing antibiotic resistance pattern, which requires the development of novel antimicrobials capable of controlling ST. Polyphenolic compounds found in plant extracts are strong candidates as alternative antimicrobials, particularly phenolic acids such as gallic acid (GA), protocatechuic acid (PA) and vanillic acid (VA). This study evaluates the effectiveness of these compounds in inhibiting ST growth while determining changes to the outer membrane through fluorescent dye uptake and scanning electron microscopy (SEM), in addition to measuring alterations to virulence genes with qRT-PCR. Results showed antimicrobial potential for all compounds, significantly inhibiting the detectable growth of ST. Fluorescent spectrophotometry and microscopy detected an increase in relative fluorescent intensity (RFI) and red-colored bacteria over time, suggesting membrane permeabilization. SEM revealed severe morphological defects at the polar ends of bacteria treated with GA and PA, while VA-treated bacteria were found to be mid-division. Relative gene expression showed significant downregulation in master regulator hilA and invH after GA and PA treatments, while fliC was upregulated in VA. Results suggest that GA, PA and VA have antimicrobial potential that warrants further research into their mechanism of action and the interactions that lead to ST death.

Growth Inhibition and Alternation of Virulence Genes of Salmonella on Produce Products Treated with Polyphenolic Extracts from Berry Pomace.

ABSTRACT: Organic farming, including integrated crop-livestock farms and backyard farming, is gaining popularity in the United States, and products from these farms are commonly sold at farmers' markets, local stores, and roadside stalls. Because organic farms avoid using antibiotics and chemicals and because they use composted animal waste and nonprofessional harvesting and packaging methods, their products have an increased risk of cross-contamination with zoonotic pathogens. This study sets out to evaluate the efficiency of new postharvest disinfection processes using natural berry pomace extracts (BPEs) as a means to reduce the bacterial load found in two common leafy greens, spinach and celery. Spinach and celery were inoculated with a fixed bacterial load of Salmonella Typhimurium and later were soaked in BPE-supplemented water (wBPE) for increasing periods of time, at two different temperatures (24 and 4°C). The remaining live bacteria were quantified (log CFU per leaf), and numbers were compared with those on vegetables soaked in water alone. The relative expression of virulence genes (hilA1/C1/D1, invA1/C1/E1/F1) of wBPE-treated Salmonella Typhimurium was determined. For spinach, there was a significant (P < 0.05) reduction of Salmonella Typhimurium: 0.2 to 1.2 log CFU/mL and 0.5 to 5 log CFU/mL at 24 and 4°C, respectively. For celery, there was also a significant (P < 0.05) reduction of Salmonella Typhimurium at either 24 or 4°C. The changes in relative expression of virulence genes of Salmonella Typhimurium isolated from spinach and celery varied depending on the treatment conditions but showed a significant down-regulation of inv genes when treated at 24°C for 1,440 min (P < 0.05). After seven uses, the total polyphenolic compounds in wBPE remained at an effective concentration. This research suggests that soaking these vegetables with BPE-containing water at lower temperatures can still reduce the Salmonella Typhimurium load enough to minimize the risk of infection and alter virulence properties.