Commensal Bacteria Impact on Intestinal Toll-like Receptor Signaling in Salmonella-Challenged Gnotobiotic Piglets

Gnotobiotic (GN) animals with simple and defined microbiota can help to elucidate host-pathogen interferences. Hysterectomy-derived germ-free (GF) minipigs were associated at 4 and 24 h post-hysterectomy with porcine commensal mucinolytic Bifidobacterium boum RP36 (RP36) strain or non-mucinolytic strain RP37 (RP37) or at 4 h post-hysterectomy with Lactobacillus amylovorus (LA). One-week-old GN minipigs were infected with Salmonella Typhimurium LT2 strain (LT2). We monitored histological changes in the ileum, mRNA expression of Toll-like receptors (TLRs) 2, 4, and 9 and their related molecules lipopolysaccharide-binding protein (LBP), coreceptors MD-2 and CD14, adaptor proteins MyD88 and TRIF, and receptor for advanced glycation end products (RAGE) in the ileum and colon. LT2 significantly induced expression of TLR2, TLR4, MyD88, LBP, MD-2, and CD14 in the ileum and TLR4, MyD88, TRIF, LBP, and CD14 in the colon. The LT2 infection also significantly increased plasmatic levels of inflammatory markers interleukin (IL)-6 and IL-12/23p40. The previous colonization with RP37 alleviated damage of the ileum caused by the Salmonella infection, and RP37 and LA downregulated plasmatic levels of IL-6. A defined oligo-microbiota composed of bacterial species with selected properties should probably be more effective in downregulating inflammatory response than single bacteria.

Defined Pig Microbiota with a Potential Protective Effect against Infection with Salmonella Typhimurium

A balanced microbiota is a main prerequisite for the host's health. The aim of the present work was to develop defined pig microbiota (DPM) with the potential ability to protect piglets against infection with Salmonella Typhimurium, which causes enterocolitis. A total of 284 bacterial strains were isolated from the colon and fecal samples of wild and domestic pigs or piglets using selective and nonselective cultivation media. Isolates belonging to 47 species from 11 different genera were identified by MALDI-TOF mass spectrometry (MALDI-TOF MS). The bacterial strains for the DPM were selected for anti-Salmonella activity, ability to aggregate, adherence to epithelial cells, and to be bile and acid tolerant. The selected combination of 9 strains was identified by sequencing of the 16S rRNA gene as Bacillus sp., Bifidobacterium animalis subsp. lactis, B. porcinum, Clostridium sporogenes, Lactobacillus amylovorus, L. paracasei subsp. tolerans, Limosilactobacillus reuteri subsp. suis, and Limosilactobacillus reuteri (two strains) did not show mutual inhibition, and the mixture was stable under freezing for at least 6 months. Moreover, strains were classified as safe without pathogenic phenotype and resistance to antibiotics. Future experiments with Salmonella-infected piglets are needed to test the protective effect of the developed DPM.

Release of HMGB1 and Toll-like Receptors 2, 4, and 9 Signaling Are Modulated by Bifidobacterium animalis subsp. lactis BB-12 and Salmonella Typhimurium in a Gnotobiotic Piglet Model of Preterm Infants

Gnotobiotic (GN) animals with defined microbiota allow us to study host-microbiota and microbiota-microbiota interferences. Preterm germ-free (GF) piglets were mono-associated with probiotic Bifidobacterium animalis subsp. lactis BB-12 (BB12) to ameliorate/prevent the consequences of infection with the Salmonella Typhimurium strain LT2 (LT2). Goblet cell density; expression of Toll-like receptors (TLRs) 2, 4, and 9; high mobility group box 1 (HMGB1); interleukin (IL)-6; and IL-12/23p40 were analyzed to evaluate the possible modulatory effect of BB12. BB12 prevented an LT2-induced decrease of goblet cell density in the colon. TLRs signaling modified by LT2 was not influenced by the previous association with BB12. The expression of HMGB1, IL-6, and IL12/23p40 in the jejunum, ileum, and colon and their levels in plasma were all decreased by BB12, but these changes were not statistically significant. In the colon, differences in HMGB1 distribution between the GF and LT2 piglet groups were observed. In conclusion, the mono-association of GF piglets with BB12 prior to LT2 infection partially ameliorated the inflammatory response to LT2 infection.

Histopathological Findings of Lung Cancer in Black Coal Miners in the Czech Republic

Background

Coal miners with coal workers’ pneumoconiosis (CWP, J60 according to ICD-10) were previously found to have a significantly higher risk of lung carcinoma compared to the general male population. The presented study aimed to analyze the incidence of lung carcinoma in miners, histopathological findings in cohorts with and without CWP, and effect of smoking cessation on the histopathological profile.

Methods

Analysed cohorts consisted of miners with (n = 3476) and without (n = 6687) CWP. Data on personal and working history obtained from the medical records were combined with information on lung cancer from the Czech Oncological Register and histopathological findings. Statistical analysis was performed using non-parametric tests and the incidence risk ratio (significance level of 5%).

Results

In 1992-2015, 180 miners (2.7%) without CWP and 169 (4.9%) with CWP, respectively, were diagnosed with lung carcinoma. The risk of lung cancer in miners with CWP was 1.82 (95% CI: 1.48-2.25) times higher than in those without CWP. Squamous cell carcinoma (37%) was the most common histopathological type, followed by adenocarcinoma (22%) and small cell carcinoma (21%). A statistically significant difference between the cohorts (p = 0.003) was found in the histopathological subtypes, with the incidence of small cell carcinoma being 2 times higher in miners without CWP than in those with CWP. Only a few individuals with lung carcinoma were non-smokers. The incidence of small cell carcinoma, which is strongly associated with smoking, is significantly higher in miners without CWP.

Conclusions

Smoking constitutes the most important risk factor for developing lung carcinoma even in that cohort. However, CWP remains a very important risk factor.

This work was supported by grant of Research Support Foundation, Vaduz. Markus R. Tödtli Consulting and project Healthy Aging in the Industrial Environment CZ.02.1.01/0.0/0.0/16_019/0000798 (HAIE).

Key messages

Short-term exposure to PM2.5 and hospital admissions for respiratory causes in the Czech Republic

Background and Aims

The Regions Ostrava and Karvina are the most polluted areas in the Czech Republic. The aim of this study was the analysis of effect of ambient fine particles (PM2.5) on acute hospital admissions for respiratory causes.

Methods

In the period 2013-2019, a total of 20,490 cases of acute hospitalization from respiratory causes (J00-99 according to ICD-10) was registered. The daily PM2.5 concentrations were measured at 5 stations. The analyses were performed in two ways: i) including extreme values (max. 224 μg.m-3) and ii) for PM2.5<60 μg.m-3 (5% of the highest values were cut off). The generalized additive model (GAM) for Poisson distribution was used for the analyses; the „thin plate regression spline“ was applied to smooth the pressure, relative humidity and a temperature. The model was adjusted for meteorological conditions, incidence of acute respiratory infections, days off, the order of a day in a week and the area. The calculation was done for lag0 to lag3 days. The analyses were completed using the SW Stata v.14 and SW R v.3.6.1 with the use of mgcv package v.1.8-28.

Results

The median age of patients was 57 years (IQR 4-75 years), 56% were men. The annual PM2.5 values ranged from 18.5 to 31.0 μg.m-3. Based on the fully adjusted model, a10 μg.m-3 increase in PM2.5 was associated with an increase in hospital admission of 1.0% (95% CI: 0.2-1.8%) for lag0 and lag2, 1.2% (95% CI: 0.5-1.9%) for lag3. The percentage changes for models with values of PM2.5<60 μg.m-3 were higher - 1.8% (95% CI: 0.3-3.2%) for lag0 and 3.3% (95% CI: 2.0-4.7%) for lag1-lag3.

Conclusions

The analyses confirmed the effect of ambient fine particulates (PM2.5) on acute hospital admissions for respiratory causes in the regions Ostrava and Karvina.

This presentation was supported by the project TH03030195 of the Technology Agency of the Czech Republic and the project Healthy Aging in the Industrial Environment CZ.02.1.01/0.0/0.0/16_019/0000798 (HAIE).

Key messages

• A positive association was confirmed between short-term concentrations of PM2.5 and acute hospital admissions for respiratory causes (lag0-lag3).

• No statistically significant difference was found between the identified C-R functions and C-R functions published by the WHO for the relationship between respiratory hospitalizations and PM2.5.

GIS analysis of the relationship between PM2.5 and acute CVD and respiratory hospitalizations

Background and aims

The PM air pollution is a serious concern in northern Moravia in the Czech Republic. The aim is to evaluate the risk of acute hospital admissions for cardiovascular and respiratory causes with the use of the Geographic information system (GIS).

Methods

The data on acute hospital admissions for cardiovascular (I00-99 according to ICD-10) and respiratory (J00-99) causes was assigned based on the information on residence to 77 geographical units (601,299 inhabitants). The annual concentrations of PM2.5 in the period 2013-2019 were assigned to this units according to the respective concentration iso-shapes (step 2 μg.m-3, concentrations ≤29 to ≥ 38 μg.m-3). The Incidence Rate Ratio (IRR) and 95% confidence interval (CI) was calculated for each concentration category. The incidence in the first category with the lowest PM2.5 concentrations (≤29 μg.m-3) was chosen the reference category. The statistical analyses were performed using the SW STATA v.15.

Results

About a half of population (56%) in the year 2013 belonged into the PM2.5 category 34-35 μg.m-3, 26 thousand of inhabitants (4%) live in the PM2.5 concentrations ≥38 μg.m-3. During the analysed period the average concentration values decreased from 30.8 to 21.4 μg.m-3. A statistically significant risk of the acute hospitalization for cardiovascular causes was identified in the categories ≤36 μg.m-3, in the highest interval of PM2.5 the IRR values were 2-3-fold higher comparing with the reference category. As for respiratory causes, the trend is similar, but the statistically significant risk was found already from the interval 34-35 μg.m-3.

Conclusions

With increasing concentrations, the risk of both acute cardiovascular, and respiratory hospitalizations increased.

This presentation was supported by the project TH03030195 of the Technology Agency of the Czech Republic and the project Healthy Aging in the Industrial Environment CZ.02.1.01/0.0/0.0/16_019/0000798 (HAIE).

Key messages

• A statistically significant increase of the IRR for acute cardiovascular and respiratory hospitalizations was found at PM2.5 concentrations ≤34 μg.m-3 compared to the reference category ≤29 μg.m-3.

• Average annual PM2.5 concentration decreased from 30.8 to 21.4 μg.m-3 during the followed period and also the risk of acute hospitalization from cardiovascular and respiratory causes decreased.

The order of immunoglobulin light chain κ and λ usage in primary and secondary lymphoid tissues of germ-free and conventional piglets

In pigs (Sus scrofa), the initial immunoglobulin rearrangement of the κ light chain is replaced by λ before the heavy chains rearrange, and the light chains may rearrange even later. This study investigates whether these developmental differences are reflected in the usage of IGK and IGL genes. We found large differences between peripheral B cells and those developing in the bone marrow, and between B cells in germ-free piglets and conventional pigs. During early B cell development in the bone marrow, more 3' V and 5' J gene segments for both light chains are used. However, in the peripheral naive repertoire, more 5' IGLV and 3' IGLJ genes are used. A similar shift toward the use of more 5' IGKV and 3' IGKJ genes is observed later after antigen exposure in conventional pigs. The expression profile showed that most λ⁺ B cells are generated earlier, while κ⁺ B cells develop from late precursors that already contain the λ rearrangement. The initial λ rearrangement is retained in both λ⁺ and κ⁺ B lymphocytes, and multiple λ transcripts can be found in individual cells. The overall pool of the IGLV repertoire is therefore much larger and more diversified than for IGKV. The κ repertoire is further restricted to the preferential use of only two major IGKV genes, reflecting the limitation for only two consecutive rearrangements. Tracing of silenced λ transcripts in κ⁺ B cells further confirmed the unconventional mechanism of differential rearrangements in pigs. Our results underline the diversity of the immune system among mammals.

Monoassociation of Preterm Germ-Free Piglets with Bifidobacterium animalis Subsp. lactis BB-12 and Its Impact on Infection with Salmonella Typhimurium

Preterm germ-free piglets were monoassociated with probiotic Bifidobacterium animalis subsp. lactis BB-12 (BB12) to verify its safety and to investigate possible protection against subsequent infection with Salmonella Typhimurium strain LT2 (LT2). Clinical signs of salmonellosis, bacterial colonization in the intestine, bacterial translocation to mesenteric lymph nodes (MLN), blood, liver, spleen, and lungs, histopathological changes in the ileum, claudin-1 and occludin mRNA expression in the ileum and colon, intestinal and plasma concentrations of IL-8, TNF-α, and IL-10 were evaluated. Both BB12 and LT2 colonized the intestine of the monoassociated piglets. BB12 did not translocate in the BB12-monoassociated piglets. BB12 was detected in some cases in the MLN of piglets, consequently infected with LT2, but reduced LT2 counts in the ileum and liver of these piglets. LT2 damaged the luminal structure of the ileum, but a previous association with BB12 mildly alleviated these changes. LT2 infection upregulated claudin-1 mRNA in the ileum and colon and downregulated occludin mRNA in the colon. Infection with LT2 increased levels of IL-8, TNF-α, and IL-10 in the intestine and plasma, and BB12 mildly downregulated them compared to LT2 alone. Despite reductions in bacterial translocation and inflammatory cytokines, clinical signs of LT2 infection were not significantly affected by the probiotic BB12. Thus, we hypothesize that multistrain bacterial colonization of preterm gnotobiotic piglets may be needed to enhance the protective effect against the infection with S. Typhimurium LT2.

Colonization of Germ-Free Piglets with Mucinolytic and Non-Mucinolytic Bifidobacterium boum Strains Isolated from the Intestine of Wild Boar and Their Interference with Salmonella Typhimurium

Non-typhoidal Salmonella serovars are worldwide spread foodborne pathogens that cause diarrhea in humans and animals. Colonization of gnotobiotic piglet intestine with porcine indigenous mucinolytic Bifidobacterium boum RP36 strain and non-mucinolytic strain RP37 and their interference with Salmonella Typhimurium infection were compared. Bacterial interferences and impact on the host were evaluated by clinical signs of salmonellosis, bacterial translocation, goblet cell count, mRNA expression of mucin 2, villin, claudin-1, claudin-2, and occludin in the ileum and colon, and plasmatic levels of inflammatory cytokines IL-8, TNF-α, and IL-10. Both bifidobacterial strains colonized the intestine comparably. Neither RP36 nor RP37 B. boum strains effectively suppressed signs of salmonellosis. Both B. boum strains suppressed the growth of S. Typhimurium in the ileum and colon. The mucinolytic RP36 strain increased the translocation of S. Typhimurium into the blood, liver, and spleen.

Toll-Like Receptor 4 Signaling in the Ileum and Colon of Gnotobiotic Piglets Infected with Salmonella Typhimurium or Its Isogenic ∆rfa Mutants

Salmonella Typhimurium is a Gram-negative bacterium that causes enterocolitis in humans and pigs. Lipopolysaccharide (LPS) is a component of the outer leaflet of Gram-negative bacteria that provokes endotoxin shock. LPS can be synthesized completely or incompletely and creates S (smooth) or R (rough) chemotypes. Toll-like receptors (TLR) 2, 4, and 9 initiate an inflammatory reaction to combat bacterial infections. We associated/challenged one-week-old gnotobiotic piglets with wild-type S. Typhimurium with S chemotype or its isogenic ∆rfa mutants with R chemotype LPS. The wild-type S. Typhimurium induced TLR2 and TLR4 mRNA expression but not TLR9 mRNA expression in the ileum and colon of one-week-old gnotobiotic piglets 24 h after challenge. The TLR2 and TLR4 stimulatory effects of the S. Typhimurium ∆rfa mutants were related to the completeness of their LPS chain. The transcription of IL-12/23 p40, IFN-γ, and IL-6 in the intestine and the intestinal and plasmatic levels of IL-12/23 p40 and IL-6 but not IFN-γ were related to the activation of TLR2 and TLR4 signaling pathways. The avirulent S. Typhimurium ∆rfa mutants are potentially useful for modulation of the TLR2 and TLR4 signaling pathways to protect the immunocompromised gnotobiotic piglets against subsequent infection with the virulent S. Typhimurium.

High Mobility Group Box 1 and TLR4 Signaling Pathway in Gnotobiotic Piglets Colonized/Infected with L. amylovorus, L. mucosae, E. coli Nissle 1917 and S. Typhimurium

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein that can be actively secreted by immune cells after different immune stimuli or passively released from cells undergoing necrosis. HMGB1 amplifies inflammation, and its hypersecretion contributes to multiple organ dysfunction syndrome and death. We tested possible immunomodulatory effect of commensal Lactobacillus amylovorus (LA), Lactobacillus mucosae (LM) or probiotic Escherichia coli Nissle 1917 (EcN) in infection of gnotobiotic piglets with Salmonella Typhimurium (ST). Transcription of HMGB1 and Toll-like receptors (TLR) 2, 4, and 9 and receptor for advanced glycation end products (RAGE), TLR4-related molecules (MD-2, CD14, and LBP), and adaptor proteins (MyD88 and TRIF) in the ileum and colon were measured by RT-qPCR. Expression of TLR4 and its related molecules were highly upregulated in the ST-infected intestine, which was suppressed by EcN, but not LA nor LM. In contrast, HMGB1 expression was unaffected by ST infection or commensal/probiotic administration. HMGB1 protein levels in the intestine measured by ELISA were increased in ST-infected piglets, but they were decreased by previous colonization with E. coli Nissle 1917 only. We conclude that the stability of HMGB1 mRNA expression in all piglet groups could show its importance for DNA transcription and physiological cell functions. The presence of HMGB1 protein in the intestinal lumen probably indicates cellular damage.

Impact of the Lipopolysaccharide Chemotype of Salmonella Enterica Serovar Typhimurium on Virulence in Gnotobiotic Piglets

Salmonella Typhimurium is an enteric pathogen that causes acute and chronic infections in humans and animals. One-week-old germ-free piglets were orally colonized/infected with the Salmonella Typhimurium LT2 strain or its isogenic rough ΔrfaL, ΔrfaG or ΔrfaC mutants with exactly defined lipopolysaccharide (LPS) defects. After 24 h, the piglets were euthanized and the colonization of the small intestine, translocations into the mesenteric lymph nodes, liver, spleen, lungs, and bacteremia, along with changes in the ileum histology, and transcription levels of the tight junction proteins claudin-1, claudin-2, and occludin were all assessed. Additionally, transcription levels of IL-8, TNF-α, and IL-10 in the terminal ileum, and their local and systemic protein levels were evaluated. Wild-type Salmonella Typhimurium showed the highest translocation, histopathological changes, upregulation of claudins and downregulation of occludin, transcription of the cytokines, intestinal IL-8 and TNF-α levels, and systemic TNF-α and IL-10 levels. Depending on the extent of the incompleteness of the LPS, the levels of the respective elements decreased, or no changes were observed at all in the piglets colonized/infected with Δrfa mutants. Intestinal IL-10 and systemic IL-8 levels were not detected in any piglet groups. This study provided foundational data on the gnotobiotic piglet response to colonization/infection with the exactly defined rough Salmonella Typhimurium LT2 isogenic mutants.

Colonization of Germ-Free Piglets with Commensal Lactobacillus amylovorus, Lactobacillus mucosae, and Probiotic E. coli Nissle 1917 and Their Interference with Salmonella Typhimurium

Non-typhoid Salmonellae are worldwide spread food-borne pathogens that cause diarrhea in humans and animals. Their multi-drug resistances require alternative ways to combat this enteric pathogen. Mono-colonization of a gnotobiotic piglet gastrointestinal tract with commensal lactobacilli Lactobacillus amylovorus and Lactobacillus mucosae and with probiotic E. coli Nissle 1917 and their interference with S. Typhimurium infection was compared. The impact of bacteria and possible protection against infection with Salmonella were evaluated by clinical signs, bacterial translocation, intestinal histology, mRNA expression of villin, claudin-1, claudin-2, and occludin in the ileum and colon, and local intestinal and systemic levels of inflammatory cytokines IL-8, TNF-α, and IL-10. Both lactobacilli colonized the gastrointestinal tract in approximately 100× lower density compare to E. coli Nissle and S. Typhimurium. Neither L. amylovorus nor L. mucosae suppressed the inflammatory reaction caused by the 24 h infection with S. Typhimurium. In contrast, probiotic E. coli Nissle 1917 was able to suppress clinical signs, histopathological changes, the transcriptions of the proteins, and the inductions of the inflammatory cytokines. Future studies are needed to determine whether prebiotic support of the growth of lactobacilli and multistrain lactobacilli inoculum could show higher protective effects.

Colonization of preterm gnotobiotic piglets with probiotic Lactobacillus rhamnosus GG and its interference with Salmonella Typhimurium

A balanced microbiota of the gastrointestinal tract (GIT) is a prerequisite for a healthy host. The GIT microbiota in preterm infants is determined by the method of delivery and nutrition. Probiotics can improve the GIT microbiota balance and suitable animal models are required to verify their harmlessness. Preterm gnotobiotic piglets were colonized with Lactobacillus rhamnosus GG (LGG) to evaluate its safety and possible protective action against infection with an enteric pathogen, Salmonella Typhimurium (ST). Clinical signs (anorexia, somnolence, fever and diarrhea), bacterial interference and translocation, intestinal histopathology, transcriptions of claudin-1, occludin and interferon (IFN)-γ, intestinal and systemic protein levels of interleukin (IL)-8, IL-12/23 p40 and IFN-γ were compared among (i) germ-free, (ii) LGG-colonized, (iii) ST-infected and (iv) LGG-colonized and subsequently ST-infected piglets for 24 h. Both LGG and ST-colonized the GIT; LGG translocated in some cases into mesenteric lymph nodes and the spleen but did not cause bacteremia and clinical changes. ST caused clinical signs of gastroenteritis, translocated into mesenteric lymph nodes, the spleen, liver and blood, increased claudin-1 and IFN-γ transcriptions, but decreased occludin transcription and increased local and systemic levels of IL-8 and IL-12/23 p40. Previous colonization with LGG reduced ST colonization in the jejunum and translocation into the liver, spleen and blood. It partially ameliorated histopathological changes in the intestine, reduced IL-8 levels in the jejunum and plasma and IL-12/23 p40 in the jejunum. The preterm gnotobiotic piglet model of the vulnerable preterm immunocompromised infant is useful to verify the safety of probiotics and evaluate their protective effect.

Preterm Life in Sterile Conditions: A Study on Preterm, Germ-Free Piglets

Preterm infants born with immature organ systems, which can impede normal development, can also be highly sensitive to different biological and/or environmental factors. Animal models could aid in investigating and understanding the effects of different conditions on the health of these immunocompromised infants. The epitheliochorial placentation of the pig prevents the prenatal transfer of protective colostral immunoglobulins. Surgical colostrum-deprived piglets are free of maternal immunoglobulins, and the cells that are normally provided via colostrum. We bred preterm germ-free piglets in sterile conditions and compared them with their term counterparts. Enterocyte development and intestinal morphology, tight junction proteins claudin-1 and occludin, pattern-recognizing receptors, adaptor molecules and coreceptors (RAGE, TLR2, TLR4, TLR9, MyD88, TRIF, MD2, and CD14), and inflammasome NLRP3 transcription were all evaluated. The production of inflammatory mediators IFN-α, IL-4, IL-6, IL-8, IL-10, IL-12/23 p40, TNF-α, IFN-γ, and high mobility group box 1 (HMGB1) in the intestine of germ-free piglets was also assessed. In the preterm germ-free piglets, the ileum showed decreased lamina propria cellularity, reduced villous height, and thinner and less distinct stratification - especially muscle layer, in comparison with their term counterparts. Claudin-1 transcription increased in the intestine of the preterm piglets. The transcription levels of pattern-recognizing receptors and adaptor molecules showed ambiguous trends between the groups. The levels of IL-6, IL-8, IL-10, and TNF-α were increased in the preterm ileum numerically (though not significantly), with statistically significant increases in the colon. Additionally, IL-12/23 p40 and IFN-γ were statistically significantly higher in the preterm colon. Both blood plasma and intestinal HMGB1 levels were nonsignificantly higher in the preterm group. We propose that the intestine of the preterm germ-free piglets showed "mild inflammation in sterile conditions." This model, which establishes preterm, hysterectomy-derived germ-free piglets, without protective maternal immunoglobulins, can be used to study influences of microbiota, nutrition, and therapeutic interventions on the development and health of vulnerable immunocompromised preterm infants.

A modified MacConkey agar for selective enumeration of necrotoxigenic E. coli O55 and probiotic E. coli Nissle 1917

An agar selective enumeration of necrotoxigenic Escherichia coli O55 (NTEC2) and probiotic E. coli Nissle 1917, using modified MacConkey agar, was developed to study bacterial interference between these E. coli strains in a gnotobiotic piglet model. Replacement of lactose with saccharose in the agar enables the direct visual enumeration of red colonies of E. coli O55 and yellow colonies of E. coli Nissle 1917 that are co-cultured in the same Petri dish. A total of 336 colonies (168 for each color) were subjected to strain-specific PCR identification with LNA probes. Sensitivity, specificity, and positive and negative predictive values were 96.43%, 95.83%, 95.86% and 96.41% respectively in E. coli O55, and 98.21%, 97.02%, 97.06% and 98.19% respectively in E. coli Nissle 1917. Color-based enumeration of both E. coli strains in colonic contents and mesenteric lymph nodes homogenates of gnotobiotic piglets demonstrated the applicability of this method for the gnotobiotic piglet model of enteric diseases.

Local and systemic occurrences of HMGB1 in gnotobiotic piglets infected with E. coli O55 are related to bacterial translocation and inflammatory cytokines

High mobility group box 1 (HMGB1), a nuclear protein, can be secreted by stimulated cells or released from damaged cells. It is recognized as a late mediator of sepsis, but its extracellular occurrence has primarily been studied on the systemic level. Acute and chronic diseases of the gastrointestinal tract, however, have usually been connected with immediate local cell damage. We present local and systemic findings of HMGB1 in Escherichia coli O55-caused infection, in relation to inflammatory cytokines, using a pig gnotobiotic infection model. High levels of HMGB1 were detected in the intestine of those piglets that suffered from infection (fever, anorexia, and diarrhea), as compared to their E. coli 055-infected counterparts that thrived. These local changes were also reflected at the systemic level and related to inflammatory cytokines. Based on our findings of high levels of HMGB1 in the intestinal content of the infection-suffering gnotobiotic piglets, its concurrent presence with inflammatory cytokines, and the published literature, we propose that the detection and analysis of HMGB1 levels in feces can be a non-invasive method of clinical evaluation of the severity of enteric infections.

Alarmin HMGB1 is released in the small intestine of gnotobiotic piglets infected with enteric pathogens and its level in plasma reflects severity of sepsis

OBJECTIVES

Alarmin high mobility group box 1 (HMGB1) is essential for correct DNA folding and transcription. It can be released from damaged cells or secreted by stimulated cells. HMGB1 has been detected in serum or plasma as a late marker of sepsis, but its suitability as a marker of sepsis has been disputed.

METHODS

One-week-old germ-free piglets were orally infected/colonized with enteric bacterial pathogens (Salmonella Typhimurium or Escherichia coli O55) or with probiotic bacteria (E. coli Nissle 1917) for 24 h. The transcriptions of HMGB1, interleukin (IL)-8, tumor necrosis factor (TNF)-α, and IL-10 (quantitative reverse transcription and polymerase chain reaction), their protein levels (ELISA), and clinical state of the piglets (somnolence, anorexia, diarrhea, tachycardia, tachypnea, and tremor) were estimated.

RESULTS

The piglets infected with enteric pathogens suffered from infections. HMGB1 was transcribed in the terminal ileum constitutively, regardless of any bacterial presence. In contrast, the transcription of cytokines was upregulated by virulent bacteria. HMGB1, IL-8, and TNF-α levels in the ileum were increased by both enteric pathogens, while IL-10 levels increased in E. coli O55-infected piglets only. HMGB1 significantly increased in the plasma of piglets infected with virulent E. coli only, but cytokine levels were in most cases increased by both virulent bacteria. HMGB1 and cytokine levels in ileum lavages and plasma of piglets colonized with probiotic E. coli remained comparable to those of the non-stimulated germ-free piglets.

CONCLUSION

The local and systemic expression of HMGB1, its relationship to the inflammatory cytokines, and clinical findings showed HMGB1 as a suitable marker of severity of sepsis in the gnotobiotic piglet infection model.

Interference of Bifidobacterium choerinum or Escherichia coli Nissle 1917 with Salmonella Typhimurium in gnotobiotic piglets correlates with cytokine patterns in blood and intestine

The colonization, translocation and protective effect of two intestinal bacteria - PR4 (pig commensal strain of Bifidobacterium choerinum) or EcN (probiotic Escherichia coli strain Nissle 1917) - against subsequent infection with a virulent LT2 strain of Salmonella enterica serovar Typhimurium were studied in gnotobiotic pigs after oral association. The clinical state of experimental animals correlated with bacterial translocation and levels of inflammatory cytokines [a chemokine, interleukin (IL)-8, a proinflammatory cytokine, tumour necrosis factor (TNF)-α and an anti-inflammatory cytokine, IL-10] in plasma and intestinal lavages. Gnotobiotic pigs orally mono-associated with either PR4 or EcN thrived, and bacteria were not found in their blood. No significant inflammatory cytokine response was observed. Mono-association with Salmonella caused devastating septicaemia characterized by high levels of IL-10 and TNF-α in plasma and TNF-α in the intestine. Di-associated gnotobiotic pigs were given PR4 or EcN for 24 h. Subsequently, they were infected orally with Salmonella and euthanized 24 h later. Pigs associated with bifidobacteria before Salmonella infection suffered from severe systemic infection and mounted similar cytokine responses as pigs infected with Salmonella alone. In contrast, EcN interfered with translocation of Salmonella into mesenteric lymph nodes and systemic circulation. Pigs pre-associated with EcN thrived and their clinical condition correlated with the absence of IL-10 in their plasma and a decrease of TNF-α in plasma and ileum.

Modulation of natural immunity in the gut by Escherichia coli strain Nissle 1917

The beneficial effect of probiotic Escherichia coli strain Nissle 1917 (EcN) suggests the gut epithelium plays a basic role in immune interactions with bacteria. Contrary to other commensal strains of Escherichia coli, EcN profoundly modulates the gut barrier to elevate its resistance to microbial pathogens. The present review documents the properties of EcN that have led to the protection of gnotobiotic pigs against lethal enteric infections. This effect could be important in light of the growing number of acquired deficiencies that paralyze gut immunity in humans.

Cytokine response to Escherichia coli in gnotobiotic pigs

One-week-old-germ-free pigs were inoculated with 10(8) CFU of E.coli bacteria-either commensal 086 strain or virulent 055 strain for 1 d. Bacteria were counted in the small intestine, mesenteric lymph nodes, blood and lungs. The O55 strain reached higher levels in circulation and lungs. IL-8, IL-10 and TNF-alpha concentrations were determined by ELISA in plasma and intestinal washes . No difference in cytokine levels was found between control germ-free pigs and their counterparts associated with commensal O86 strain in spite of its high concentration in the gut and circulation.

Susceptibility of germ-free pigs to challenge with protease mutants of Salmonella enterica serovar Typhimurium

Salmonella protease mutants, clpP and especially htrA, are candidate live oral vaccines in humans. A functional and mature immune system is, however, required to cope with them in mice. Here, we test the cytokine response of highly susceptible germ-free pigs to infection with Salmonella Typhimurium clpP and htrA mutants. Cytokine levels (IL-4, IL-10, IL-18 and IFN-gamma) were measured by ELISA in plasma and washes from the terminal small bowel 24h after oral challenge. Unlike the infection with the wild type strain, no IFN-gamma response and low IL-18 intestinal levels were found in pigs infected with the protease mutants. Despite this and regardless of partially reduced ability of htrA and clpP mutants to invade and multiply in a 3D4 porcine macrophage-like cell line, both the mutants were as virulent as was the wild type LT2 strain and caused fatal septicaemia in germ-free pigs. IFN-gamma and IL-18 response therefore did not correlate with the virulence of Salmonella Typhimurium. Our results indicate that htrA and clpP attenuations should be used with caution in populations in which an increased number of immunocompromised individuals can be expected.

Attenuated aroA Salmonella enterica serovar Typhimurium does not induce inflammatory response and early protection of gnotobiotic pigs against parental virulent LT2 strain

Cytokine and inflammatory response against virulent LT2 strain and its attenuated aroA deletion mutant of Salmonella enterica serovar Typhimurium were compared in gnotobiotic pigs. Contrary to the parental strain, the auxotrofic mutant did not induce IL-1beta, IL-18, TNF-alpha, and IFN-gamma in the ileum and plasma 24h after the infection, did not cause pathological changes in ileal epithelium and mesenteric lymph nodes or immunoreactivity of gp91 phox and peroxynitrite and was not immunostained for GroEL stress protein. The absence of induction of proinflammatory cytokines may be a reason why aroA mutant was unable to elicit any inflammatory response and protect pigs against challenge with virulent LT2 strain administered 24h later.