In this study, the effect of sustainable probiotics on Campylobacter jejuni colonization and gut microbiome composition was evaluated using chicken as a model organism. Chickens were given Lactobacillus casei over-expressing myosin-cross-reactive antigen (LC+mcra). LC+mcra can generate bioactive compounds in larger quantity including conjugated linoleic acid. A total of 120 chickens were used in duplicate trials to investigate the effectiveness of LC+mcra in decreasing C. jejuni colonization by means of kanamycin resistant strain compared to the control group. We observed that LC+mcra can efficiently colonize various parts of the chicken gut and competitively reduce colonization of natural and challenged C. jejuni and natural Salmonella enterica. LC+mcra was found to reduce C. jejuni colonization in cecum, ileum and jejunum, by more than one log CFU/g when compared to the no-probiotic control group. Furthermore, 16S rRNA compositional analysis revealed lower abundance of Proteobacteria, higher abundance of Firmicutes, along with enriched bacterial genus diversity in gut of LC+mcra fed chicken. Decreased contamination of drinking water by C. jejuni and S. enterica was also observed, suggesting a potential function of reducing horizontal transfer of enteric bacteria in poultry. Outcomes of this study reveal high potential of LC+mcra as sustainable approach to decrease colonization of C. jejuni and S. enterica in poultry gut along with other beneficial attributes.

No abstract

Enhancing extracellular metabolic byproducts of probiotics is one of the promising strategies to improve overall host health as well as to control enteric infections caused by various foodborne pathogens. However, the underlying mechanism of action of those metabolites and their effective concentrations are yet to be established. In this study, we determined the antibacterial potential of the metabolites in the cell-free culture supernatant (CFCS) collected from wild-type Lactobacillus casei (LCwt) and genetically modified LC to overexpress linoleate isomerase (LCCLA). We also evaluated the mechanism of action of CFCSs collected from the culture of LCwt in the presence or absence of 0.5% peanut flour (CFCSwt and CFCSwt+PF, respectively) and LCCLA alone (CFCSCLA) against enterohemorrhagic Escherichia coli (EHEC). The metabolites present in CFCSwt+PF and CFCSCLA eliminated EHEC within 24 and 48 h, respectively. Whereas CFCSwt failed to eliminate EHEC but reduced their growth by 6.7 logs (p < 0.05) as compared to the control. Significant downregulation of the expression of cell division gene, ftsZ, supported the observed degree of bactericidal and bacteriostatic properties of the collected CFCSs. Upregulation of EHEC genes related to maintaining cell membrane integrity, DNA damage repair, and molecular chaperons indicated an intensive stress condition imposed by the total metabolites present in CFCSs on EHEC growth and cellular structures. A range of deviated morphological features provoked by the metabolites indicated a membrane-targeted action, in general, to compromise the membrane permeability of EHEC. The information obtained from this study may contribute to a more efficient prevention of EHEC related infections.

BACKGROUND: Enterohemorrhagic Escherichia coli (EHEC) is still a major foodborne bacterial infectious agent in the USA and causes both diarrheal disease and hemolytic uremic syndrome (HUS). As antibiotic therapy is not an option, appropriate antimicrobial or inhibitor against EHEC colonization/infections is urgently needed. OBJECTIVE: Develop an appropriate natural antimicrobial and stimulate host defense to control foodborne illnesses with EHEC. METHOD: We investigated the role of chokeberry (Aronia melanocarpa) pomace (byproducts) extract (CPE) on growth and survival of EHEC EDL-933, probiotics specifically Lactobacillus, and other common gut bacterial flora including Streptococcus thermophilus, Enterococcus faecalis and Bacillus subtilis. We also tested the effects of CPE on physicochemical properties, host cells-EHEC interactions, and expression of various virulence genes of EHEC. RESULTS:The growth of EHEC EDL-933 was reduced by 4 logs in the presence of 0.5 mg GAE/mL CPE at 5 hr while this concentration promoted the growth of Lactobacillus and common gut bacterial flora, S. thermophillus, E. faealis and B. subtilis. The abilities of EHEC to attach and invade host intestinal epithelial (INT-407) cells were also reduced significantly (p < 0.05) which was supported by alternation physiological properties of EHEC and virulence genes expression. CONCLUSION: These results suggest that CPE has the potential to be an effective therapeutic/preventive for EHEC EDL-933 without affecting the common gut microflora and probiotics.

Probiotics in fermented foods or commercially available supplements benefit the host by providing metabolites and peptides. The production of these metabolites varies with the available substrates or prebiotics present in the system and their concentration. In this study, 0.5% peanut flour (PF) was used to stimulate the growth and production of metabolites of wild-type Lactobacillus casei (LCwt) and compare with an engineered L. casei (LCCLA) capable of converting a higher amount of conjugated linoleic acid (CLA). The total extracellular metabolites present in the cell-free cultural supernatant (CFCS) of LCwt (without peanut), LCwt+PF (with peanut), and LCCLA were collected after 24 and 48 h of incubation, and their antagonistic activities against enterohemorrhagic Escherichia coli (EHEC EDL933) growth and pathogenesis were evaluated. All collected metabolites exhibited varying efficiency in restraining EHEC EDL933 growth, whereas supplementing a low concentration of CLA to the 48-h CFCS from LCwt showed augmented antagonism toward EHEC EDL933. A downregulation of key virulence genes was observed from metabolites collected at the 48-h time point. These observations indicate that the presence of metabolites in CFCSs—including CLA, which is produced by Lactobacillus and was identified by gas chromatography–mass spectrometry—plays a critical role. This study demonstrates the potential applicability of Lactobacillus-originated CLA in the prevention of EHEC EDL933–mediated illnesses. HIGHLIGHTS