Response of porcine intestinal in vitro organ culture tissues following exposure to Lactobacillus plantarum JC1 and Salmonella enterica serovar Typhimurium SL1344

The Game for Three: Salmonella–Host–Microbiota Interaction Models

Colonization of the gastrointestinal (GI) tract by enteric pathogens occurs in a context strongly determined by host-specific gut microbiota, which can significantly affect the outcome of infection. The complex gameplay between the trillions of microbes that inhabit the GI tract, the host, and the infecting pathogen defines a specific triangle of interaction; therefore, a complete model of infection should consider all of these elements. Many different infection models have been developed to explain the complexity of these interactions. This review sheds light on current knowledge, along with the strengths and limitations of in vitro and in vivo models utilized in the study of Salmonella–host–microbiome interactions. These models range from the simplest experiment simulating environmental conditions using dedicated growth media through in vitro interaction with cell lines and 3-D organoid structure, and sophisticated “gut on a chip” systems, ending in various animal models. Finally, the challenges facing this field of research and the important future directions are outlined.

Protective Effect of Potential Probiotic Strains from Fermented Ethiopian Food against Salmonella Typhimurium DT104 in Mice

Salmonella is one of the most harmful pathogens responsible for foodborne outbreaks, illnesses and deaths. The aim of this study was to evaluate the effect of potentially probiotic strains against Salmonella Typhimurium DT104 in mice. The compatibility test among the selected potential probiotic strains (Lactobacillus plantarum K132, Lactobacillus paracasei K114 and Lactococcus lactis E124) using the cross-streaking method showed the absence of antagonism. The anti-Salmonella activities of coculture of the isolated potential probiotics in the form of mixed or single culture showed a remarkable anti-Salmonella activity with 96.50 to 100% growth inhibition. The combination of strains, which showed the highest growth inhibition rates against Salmonella Typhimurium DT104, was used to test their effect on the colonization of mice by Salmonella Typhimurium DT104. White albino male mice were pretreated with the mixed potential probiotics for 7 days and infected with Salmonella Typhimurium DT104 for 1 day. A total of 3 treatments were applied, during which the negative control group was treated with phosphate-buffered saline (PBS); a positive control group (typ) was challenged with Salmonella Typhimurium DT104 alone. The treated group (pro-typ) was pretreated with mixed potential probiotic culture and then infected with Salmonella Typhimurium DT104. The survival rate of mice and counts of Salmonella in feces were recorded. The survival rate of mice on day 21 after the oral challenge with Salmonella Typhimurium DT104 was significantly (p < 0.05) higher in the experimental pro-typ group (100% survival) compared with the positive control group (20% survival). The counts (colony-forming unit per ml) of Salmonella in feces were significantly lower (p < 0.05) for the pro-typ group compared to the typ group. The combination of potential probiotic strains was able to protect mice against Salmonella Typhimurium DT104 infection that demonstrates their potential to be used as probiotic cultures for the production of functional fermented products.

Strain-specific properties of Lactobacillus plantarum for prevention of Salmonella infection

Salmonella is a common food-borne pathogen; since lactobacilli show great potential for protecting against Salmonella infections, they are used as dietary supplements in functional foods. The aim of this study is to investigate the strain-specific properties and the involved mechanisms of action of Lactobacillus plantarum towards prevention of Salmonella infection. Mice were pretreated with mixed strains or single strain of Lactobacillus plantarum for 10 d prior to infection with Salmonella typhimurium SL1344, and the survival rates showed that lactobacilli exhibited strain-specific properties for preventing Salmonella infection. Then, in vitro and in vivo studies were carried out to investigate the involved mechanism of the strain-specific properties. The results showed that different Lactobacillus plantarum strains had different effects on inhibiting Salmonella growth, thus preventing adhesion to and invasion of epithelial cells by pathogens and enhancing immune responses. The present study demonstrated strain-specific properties of probiotics to prevent Salmonella infection and elucidated their underlying mechanisms.

Infection of porcine colon explants with "Brachyspira hampsonii" leads to increased epithelial necrosis and catarrhal exudate

Mucohemorrhagic diarrhea in pigs caused by Brachyspira spp. has a global distribution, and an economic impact on affected farms due to poor performance of animals. Demonstrations that "Brachyspira hampsonii" is pathogenic have been achieved using in vivo animal models, but a critical knowledge gap exists regarding the pathogenic mechanisms employed by Brachyspira. Here, we used in vitro organ culture of porcine colon to investigate interactions between "B. hampsonii" and explants during the first 12 h of contact. Explants were either inoculated with "B. hampsonii" or sterile culture broth. Responses to infection were evaluated by optical microscopy and quantitative PCR. Significantly greater numbers of necrotic crypt cells and thicker catarrhal exudate were observed on infected explants compared to controls. Spirochaetes were observed in the mucus layer, in contact with necrotic exfoliated cells, in crypts and the lamina propria. Statistical differences were observed in mRNA levels between inoculated and control explants for IL-1α, TNF-α and ZO-1 using a Bayesian analysis, but not observed using the ΔΔCq method. These results provide a demonstration of a porcine colon explant model for investigating interactions of Brachyspira with its host and show that initial effects on the host are observed within the first 12 h of contact.

Development and evaluation of a porcine in vitro colon organ culture technique

The intestinal mucosa comprises a complex assemblage of specialized tissues that interact in numerous ways. In vitro cell culture models are generally focused on recreating a specific characteristic of this organ and do not account for the many interactions between the different tissues. In vitro organ culture (IVOC) methods offer a way to overcome these limitations, but prolonging cell viability is essential. This study aimed to determine the feasibility and optimal conditions for in vitro culture of swine colonic mucosa for use as an enteric pathogen infection model. Explants (n = 168) from commercial pigs (n = 12), aged 5 to 10 wk, were used to assess the impact of various culture protocols on explant viability. Explants were cultured for up to 5 d and formalin fixed at 24-h intervals. Following establishment of the culture protocol, explants (n = 208) from 13 pigs were evaluated at Day 0 and 5 of culture. Assessment of viability was based on histological changes (tissue architecture evaluated by H&E, immunostaining of cell proliferation marker Ki-67) and expression of genes encoding IL-1α, IL-8, TNF-α, IFN-γ, and e-cadherin. After 5 d in culture, 20% of explants displayed over 80% of epithelial coverage, whereas 31% of explants had more than 50% of their surface covered by columnar epithelium, and 81% had crypts but with a decreased number of Ki-67-positive cells when compared to Day 0. Notably, large variability in explant quality was observed between donor pigs. Best possible explants were obtained from the distal colon of pigs, processed immediately after euthanasia, cultured at the liquid-tissue-gas interface in media supplemented with a mixture of antibiotics and antifungals and an oxygen-rich gas mix.

New mass-spectrometry-compatible degradable surfactant for tissue proteomics

Tissue proteomics is increasingly recognized for its role in biomarker discovery and disease mechanism investigation. However, protein solubility remains a significant challenge in mass spectrometry (MS)-based tissue proteomics. Conventional surfactants such as sodium dodecyl sulfate (SDS), the preferred surfactant for protein solubilization, are not compatible with MS. Herein, we have screened a library of surfactant-like compounds and discovered an MS-compatible degradable surfactant (MaSDeS) for tissue proteomics that solubilizes all categories of proteins with performance comparable to SDS. The use of MaSDeS in the tissue extraction significantly improves the total number of protein identifications from commonly used tissues, including tissue from the heart, liver, and lung. Notably, MaSDeS significantly enriches membrane proteins, which are often under-represented in proteomics studies. The acid degradable nature of MaSDeS makes it amenable for high-throughput MS-based proteomics. In addition, the thermostability of MaSDeS allows for its use in experiments requiring high temperature to facilitate protein extraction and solubilization. Furthermore, we have shown that MaSDeS outperforms the other MS-compatible surfactants in terms of overall protein solubility and the total number of identified proteins in tissue proteomics. Thus, the use of MaSDeS will greatly advance tissue proteomics and realize its potential in basic biomedical and clinical research. MaSDeS could be utilized in a variety of proteomics studies as well as general biochemical and biological experiments that employ surfactants for protein solubilization.

SPI-23 of S. Derby: role in adherence and invasion of porcine tissues

Salmonella enterica serovars Derby and Mbandaka are isolated from different groups of livestock species in the UK. S. Derby is predominantly isolated from pigs and turkeys and S. Mbandaka is predominantly isolated from cattle and chickens. Alignment of the genome sequences of two isolates of each serovar led to the discovery of a new putative Salmonella pathogenicity island, SPI-23, in the chromosome sequence of S. Derby isolates. SPI-23 is 37 kb in length and contains 42 ORFs, ten of which are putative type III effector proteins. In this study we use porcine jejunum derived cell line IPEC-J2 and in vitro organ culture of porcine jejunum and colon, to characterise the association and invasion rates of S. Derby and S. Mbandaka, and tissue tropism of S. Derby respectively. We show that S. Derby invades and associates to an IPEC-J2 monolayer in significantly greater numbers than S. Mbandaka, and that S. Derby preferentially attaches to porcine jejunum over colon explants. We also show that nine genes across SPI-23 are up-regulated to a greater degree in the jejunum compared to the colon explants. Furthermore, we constructed a mutant of the highly up-regulated, pilV-like gene, potR, and find that it produces an excess of surface pili compared to the parent strain which form a strong agglutinating phenotype interfering with association and invasion of IPEC-J2 monolayers. We suggest that potR may play a role in tissue tropism.

Lactulose and Lactobacillus plantarum, a potential complementary synbiotic to control postweaning colibacillosis in piglets

The potential of a prebiotic oligosaccharide lactulose, a probiotic strain of Lactobacillus plantarum, or their synbiotic combination to control postweaning colibacillosis in pigs was evaluated using an enterotoxigenic Escherichia coli (ETEC) K88 oral challenge. Seventy-two weanlings were fed four diets: a control diet (CTR), that diet supplemented with L. plantarum (2 × 10(10) CFU · day(-1)) (LPN), that diet supplemented with 10 g · kg(-1) lactulose (LAC), or a combination of the two treatments (SYN). After 7 days, the pigs were orally challenged. Six pigs per treatment were euthanized on days 6 and 10 postchallenge (PC). Inclusion of lactulose improved the average daily gain (ADG) (P < 0.05) and increased lactobacilli (P < 0.05) and the percentage of butyric acid (P < 0.02) in the colon. An increase in the ileum villous height (P < 0.05) and a reduction of the pig major acute-phase protein (Pig-MAP) in serum (P < 0.01) were observed also. The inclusion of the probiotic increased numbers of L. plantarum bacteria in the ileum and colon (P < 0.05) and in the total lactobacilli in the colon and showed a trend to reduce diarrhea (P = 0.09). The concentrations of ammonia in ileal and colonic digesta were decreased (P < 0.05), and the villous height (P < 0.01) and number of ileal goblet cells (P < 0.05) increased, at day 10 PC. A decrease in plasmatic tumor necrosis factor alpha (TNF-α) (P < 0.01) was also seen. The positive effects of the two additives were combined in the SYN treatment, resulting in a complementary synbiotic with potential to be used to control postweaning colibacillosis.

Lactobacilli antagonize the growth, motility, and adherence of Brachyspira pilosicoli: a potential intervention against avian intestinal spirochetosis

Avian intestinal spirochetosis (AIS) results from the colonization of the ceca and colorectum of poultry by pathogenic Brachyspira species. The number of cases of AIS has increased since the 2006 European Union ban on the use of antibiotic growth promoters, which, together with emerging antimicrobial resistance in Brachyspira, has driven renewed interest in alternative intervention strategies. Probiotics have been reported as protecting livestock against infection with common enteric pathogens, and here we investigate which aspects of the biology of Brachyspira they antagonize in order to identify possible interventions against AIS. The cell-free supernatants (CFS) of two Lactobacillus strains, Lactobacillus reuteri LM1 and Lactobacillus salivarius LM2, suppressed the growth of Brachyspira pilosicoli B2904 in a pH-dependent manner. In in vitro adherence and invasion assays with HT29-16E three-dimensional (3D) cells and in a novel avian cecal in vitro organ culture (IVOC) model, the adherence and invasion of B. pilosicoli in epithelial cells were reduced significantly by the presence of lactobacilli (P < 0.001). In addition, live and heat-inactivated lactobacilli inhibited the motility of B. pilosicoli, and electron microscopic observations indicated that contact between the lactobacilli and Brachyspira was crucial in inhibiting both adherence and motility. These data suggest that motility is essential for B. pilosicoli to adhere to and invade the gut epithelium and that any interference of motility may be a useful tool for the development of control strategies.