Rupture, invasion and inflammatory destruction of the intestinal barrier by Shigella: the yin and yang of innate immunity

Sulfated Chinese Yam Polysaccharides Alleviate LPS-Induced Acute Inflammation in Mice through Modulating Intestinal Microbiota

This study aimed to test the preventive anti-inflammatory properties of Chinese yam polysaccharides (CYP) and sulfated Chinese yam polysaccharides (SCYP) on LPS-induced systemic acute inflammation in mice and investigate their mechanisms of action. The results showed that SCYP can efficiently reduce plasma TNF-α and IL-6 levels, exhibiting an obvious anti-inflammation ability. Moreover, SCYP reduced hepatic TNF-α, IL-6, and IL-1β secretion more effectively than CYP, and significantly altered intestinal oxidative stress levels. In addition, a 16S rRNA gene sequencing analysis showed that CYP regulated the gut microbiota by decreasing Desulfovibrio and Sutterella and increasing Prevotella. SCYP changed the gut microbiota by decreasing Desulfovibrio and increasing Coprococcus, which reversed the microbiota dysbiosis caused by LPS. Linear discriminant analysis (LDA) effect size (LEfSe) revealed that treatment with CYP and SCYP can produce more biomarkers of the gut microbiome that can promote the proliferation of polysaccharide-degrading bacteria and facilitate the intestinal de-utilization of polysaccharides. These results suggest that SCYP can differentially regulate intestinal flora, and that they exhibit anti-inflammatory effects, thus providing a new reference to rationalize the exploitation of sulfated yam polysaccharides.

Gut Microbiota as a Potential Predictive Biomarker in Relapsing-Remitting Multiple Sclerosis

BACKGROUND

The influence of the microbiome on neurological diseases has been studied for years. Recent findings have shown a different composition of gut microbiota detected in patients with multiple sclerosis (MS). The role of this dysbiosis is still unknown.

OBJECTIVE

We analyzed the gut microbiota of 15 patients with active relapsing-remitting multiple sclerosis (RRMS), comparing with diet-matched healthy controls.

METHOD

To determine the composition of the gut microbiota, we performed high-throughput sequencing of the 16S ribosomal RNA gene. The specific amplified sequences were in the V3 and V4 regions of the 16S ribosomal RNA gene.

RESULTS

The gut microbiota of RRMS patients differed from healthy controls in the levels of the Lachnospiraceae, Ezakiella, Ruminococcaceae, Hungatella, Roseburia, Clostridium, Shuttleworthia, Poephyromonas, and Bilophila genera. All these genera were included in a logistic regression analysis to determine the sensitivity and the specificity of the test. Finally, the ROC (receiver operating characteristic) and AUC with a 95% CI were calculated and best-matched for Ezakiella (AUC of 75.0 and CI from 60.6 to 89.4) and Bilophila (AUC of 70.2 and CI from 50.1 to 90.4).

CONCLUSIONS

There is a dysbiosis in the gut microbiota of RRMS patients. An analysis of the components of the microbiota suggests the role of some genera as a predictive factor of RRMS prognosis and diagnosis.

The tale of the traveling cheese: Shigella in a lung transplant patient

Shigellae are Gram-negative, nonmotile, facultatively anaerobic, non-spore-forming rods. Shigella is a common cause of gastroenteritis in areas of overcrowding and poor sanitation, but is seen less frequently in the developed world. Infection is mainly acquired through the fecal-oral route, but consumption of unpasteurized dairy remains a high risk for transmission. In the developing world, Shigella is a childhood illness and with adequate hydration is fairly self-limiting. The use of antibiotics depends on the severity of illness, the age of the patient and immune status. In immunocompromised patients, chronic symptomatic or relapsing infection has been described. In this report, we describe a case of a lung transplant patient, one year out of his transplant, on triple immunosuppressive therapy, who presented with septic shock secondary to Shigella gastroenteritis after ingesting unpasteurized cheese brought back from Peru. This case highlights the importance of educating transplant patients on how to reduce certain harmful exposures that may be fatal in immunosuppressed individuals.

Effect of Psidium guajava (guava) L. Leaf Decoction on Antibiotic-resistant Clinical Diarrhoeagenic Isolates of Shigella spp

Background: Although shigellosis is self-limiting, antibiotics are recommended to minimize the severity of symptoms and reduce mortality rates. However, due to the increasing reports of antibiotic resistance, alternative approaches are needed to combat shigellosis. Interest for research on medicinal plants has increased in recent years, and hence, they can be explored to treat this infectious diarrhoea. Objective: To study the effect of Psidium guajava L. (guava) leaf decoction (GLD) on the antibiotic-resistant clinical isolates of Shigella spp. Materials and Methods: A total of 43 isolated Shigella spp. from diarrhoeal patients were used in this study. The effect of GLD on the bacterial viability was initially assessed. The isolates were divided into two categories: sensitive and resistant to GLD. For sensitive isolates, antibacterial activity of GLD was evaluated while for resistant strains, the ability of GLD for reducing the bacterial invasion of the HEp-2 cell line underwent an investigation. Results: Among the 43 Shigella isolates, GLD affected the growth of 23 strains. The invasion of 9 strains from the 20 remaining resistant isolates was unaffected. Although the number of isolates was less, the data suggested that isolates belonging to S. flexneri serogroup were more sensitive to GLD in comparison with other spp (i.e., sonnei, boydii, and dysenteriae). Conclusion: The results of this study revealed the efficacy of GLD against drug-resistant Shigella spp. and thus could be considered for the treatment of diarrhoea. GLD can be a cost-effective alternative to antibiotics.

Multiple proteins arising from a single gene: The role of the Spa33 variants in Shigella T3SS regulation

Shigella invasion and dissemination in intestinal epithelial cells relies on a type 3 secretion system (T3SS), which mediates translocation of virulence proteins into host cells. T3SSs are composed of three major parts: an extracellular needle, a basal body, and a cytoplasmic complex. Three categories of proteins are hierarchically secreted: (a) the needle components, (b) the translocator proteins which form a pore (translocon) inside the host cell membrane and (c) the effectors interfering with the host cell signaling pathways. In the absence of host cell contact, the T3SS is maintained in an “off” state by the presence of a tip complex. Secretion is activated by host cell contact which allows the release of a gatekeeper protein called MxiC. In this work, we have investigated the role of Spa33, a component of the cytoplasmic complex, in the regulation of secretion. The spa33 gene encodes a 33‐kDa protein and a smaller fragment of 12 kDa (Spa33^C) which are both essential components of the cytoplasmic complex. We have shown that the spa33 gene gives rise to 5 fragments of various sizes. Among them, three are necessary for T3SS. Interestingly, we have shown that Spa33 is implicated in the regulation of secretion. Indeed, the mutation of a single residue in Spa33 induces an effector mutant phenotype, in which MxiC is sequestered. Moreover, we have shown a direct interaction between Spa33 and MxiC.

A murine model of diarrhea, growth impairment and metabolic disturbances with Shigella flexneri infection and the role of zinc deficiency

Shigella is one of the major enteric pathogens worldwide. We present a murine model of S. flexneri infection and investigate the role of zinc deficiency (ZD). C57BL/6 mice fed either standard chow (HC) or ZD diets were pretreated with an antibiotic cocktail and received S. flexneri strain 2457T orally. Antibiotic pre-treated ZD mice showed higher S. flexneri colonization than non-treated mice. ZD mice showed persistent colonization for at least 50 days post-infection (pi). S. flexneri-infected mice showed significant weight loss, diarrhea and increased levels of fecal MPO and LCN in both HC and ZD fed mice. S. flexneri preferentially colonized the colon, caused epithelial disruption and inflammatory cell infiltrate, and promoted cytokine production which correlated with weight loss and histopathological changes. Infection with S. flexneri ΔmxiG (critical for type 3 secretion system) did not cause weight loss or diarrhea, and had decreased stool shedding duration and tissue burden. Several biochemical changes related to energy, inflammation and gut-microbial metabolism were observed. Zinc supplementation increased weight gains and reduced intestinal inflammation and stool shedding in ZD infected mice. In conclusion, young antibiotic-treated mice provide a new model of oral S. flexneri infection, with ZD promoting prolonged infection outcomes.

The inner-rod component of Shigella flexneri type 3 secretion system, MxiI, is involved in the transmission of the secretion activation signal by its interaction with MxiC

The virulence of Shigella mainly resides in the use of a Type 3 Secretion System (T3SS) to inject several proteins inside the host cell. Three categories of proteins are hierarchically secreted: (1) the needle components (MxiH and MxiI), (2) the translocator proteins which form a pore (translocon) inside the host cell membrane, and (3) the effectors interfering with the host cell signaling pathways. In the absence of host cell contact, the T3SS is maintained in an “off” state by the presence of a tip complex. We have previously identified a gatekeeper protein, MxiC, which sequesters effectors inside the bacteria probably by interacting with MxiI, the inner‐rod component. Upon cell contact and translocon insertion, a signal is most likely transmitted from the top of the needle to the base, passing through the needle and allowing effectors release. However, the molecular mechanism underlying the transmission of the activation signal through the needle is still poorly understood. In this work, we investigate the role of MxiI in the activation of the T3SS by performing a mutational study. Interestingly we have shown that mutations of a single residue in MxiI (T82) induce an mxiC‐like phenotype and prevent the interaction with MxiC. Moreover, we have shown that the L26A mutation significantly reduces T3 secretion. The L26A mutation impairs the interaction between MxiI and Spa40, a keystone component of the switch between needle assembly and translocators secretion. The L26A mutation also sequesters MxiC. All these results highlight the crucial role of MxiI in regulating the secretion and transmitting the activation signal of the T3SS.

Escherichia albertii, a novel human enteropathogen, colonizes rat enterocytes and translocates to extra-intestinal sites

Diarrhea is the second leading cause of death of children up to five years old in the developing countries. Among the etiological diarrheal agents are atypical enteropathogenic Escherichia coli (aEPEC), one of the diarrheagenic E. coli pathotypes that affects children and adults, even in developed countries. Currently, genotypic and biochemical approaches have helped to demonstrate that some strains classified as aEPEC are actually E. albertii, a recently recognized human enteropathogen. Studies on particular strains are necessary to explore their virulence potential in order to further understand the underlying mechanisms of E. albertii infections. Here we demonstrated for the first time that infection of fragments of rat intestinal mucosa is a useful tool to study the initial steps of E. albertii colonization. We also observed that an E. albertii strain can translocate from the intestinal lumen to Mesenteric Lymph Nodes and liver in a rat model. Based on our finding of bacterial translocation, we investigated how E. albertii might cross the intestinal epithelium by performing infections of M-like cells in vitro to identify the potential in vivo translocation route. Altogether, our approaches allowed us to draft a general E. albertii infection route from the colonization till the bacterial spreading in vivo.

The Impact of Oxygen on Bacterial Enteric Pathogens

Bacterial enteric pathogens are responsible for a tremendous amount of foodborne illnesses every year through the consumption of contaminated food products. During their transit from contaminated food sources to the host gastrointestinal tract, these pathogens are exposed and must adapt to fluctuating oxygen levels to successfully colonize the host and cause diseases. However, the majority of enteric infection research has been conducted under aerobic conditions. To raise awareness of the importance in understanding the impact of oxygen, or lack of oxygen, on enteric pathogenesis, we describe in this review the metabolic and physiological responses of nine bacterial enteric pathogens exposed to environments with different oxygen levels. We further discuss the effects of oxygen levels on virulence regulation to establish potential connections between metabolic adaptations and bacterial pathogenesis. While not providing an exhaustive list of all bacterial pathogens, we highlight key differences and similarities among nine facultative anaerobic and microaerobic pathogens in this review to argue for a more in-depth understanding of the diverse impact oxygen levels have on enteric pathogenesis.

Dietary plant extracts modulate gene expression profiles in ileal mucosa of weaned pigs after an Escherichia coli infection

This study was conducted to characterize the effects of infection with a pathogenic F-18 Escherichia coli and 3 different plant extracts on gene expression of ileal mucosa in weaned pigs. Weaned pigs (total = 64, 6.3 ± 0.2 kg BW, and 21-d old) were housed in individual pens for 15 d, 4 d before and 11 d after the first inoculation (d 0). Treatments were in a 2 × 4 factorial arrangement: with or without an F-18 E. coli challenge and 4 diets (a nursery basal, control diet [CON], 10 ppm of capsicum oleoresin [CAP], garlic botanical [GAR], or turmeric oleoresin [TUR]). Results reported elsewhere showed that the plant extracts reduced diarrhea in challenged pigs. Total RNA (4 pigs/treatment) was extracted from ileal mucosa of pigs at d 5 post inoculation. Double-stranded cDNA was amplified, labeled, and further hybridized to the microarray, and data were analyzed in R. Differential gene expression was tested by fitting a mixed linear model in a 2 × 4 factorial ANOVA. Bioinformatics analysis was conducted by DAVID Bioinformatics Resources 6.7 (DAVID; National Institute of Allergy and Infectious Diseases [NIAID, NIH], http://david.abcc.ncifcrf.gov). The E. coli infection altered (P < 0.05) the expression of 240 genes in pigs fed the CON (148 up- and 92 down-regulated). Compared with the infected CON, feeding CAP, GAR, or TUR altered (P < 0.05) the expression of 52 genes (18 up, 34 down), 117 genes (34 up- and 83 down-regulated), or 84 genes (16 up- and 68 down-regulated), respectively, often counteracting the effects of E. coli. The E. coli infection up-regulated (P < 0.05) the expression of genes related to the activation of immune response and complement and coagulation cascades, but down-regulated (P < 0.05) the expression of genes involved in protein synthesis and accumulation. Compared with the CON, feeding CAP and GAR increased (P < 0.05) the expression of genes related to integrity of membranes in infected pigs, indicating enhanced gut mucosa health. Moreover, feeding all 3 plant extracts reduced (P < 0.05) the expression of genes associated with antigen presentation or other biological processes of immune responses, indicating they attenuated overstimulation of immune responses caused by E. coli. These findings may explain why diarrhea was reduced and clinical immune responses were ameliorated in infected pigs fed plant extracts. In conclusion, plant extracts altered the expression of genes in ileal mucosa of E. coli-infected pigs, perhaps leading to the reduction in diarrhea reported previously.

Diagnostic and prognostic value of procalcitonin and C-reactive protein in malnourished children

BACKGROUND

Early recognition of bacterial infections is crucial for their proper management, but is particularly difficult in children with severe acute malnutrition (SAM). The objectives of this study were to evaluate the accuracy of C-reactive protein (CRP) and procalcitonin (PCT) for diagnosing bacterial infections and assessing the prognosis of hospitalized children with SAM, and to determine the reliability of CRP and PCT rapid tests suitable for remote settings.

METHODS

From November 2007 to July 2008, we prospectively recruited 311 children aged 6 to 59 months hospitalized with SAM plus a medical complication in Maradi, Niger. Blood, urine, and stool cultures and chest radiography were performed systematically on admission. CRP and PCT were measured by rapid tests and by reference quantitative methods using frozen serum sent to a reference laboratory.

RESULTS

Median CRP and PCT levels were higher in children with bacteremia or pneumonia than in those with no proven bacterial infection (P < .002). However, both markers performed poorly in identifying invasive bacterial infection, with areas under the curve of 0.64 and 0.67 before and after excluding children with malaria, respectively. At a threshold of 40 mg/L, CRP was the best predictor of death (81% sensitivity, 58% specificity). Rapid test results were consistent with those from reference methods.

CONCLUSIONS

CRP and PCT are not sufficiently accurate for diagnosing invasive bacterial infections in this population of hospitalized children with complicated SAM. However, a rapid CRP test could be useful in these settings to identify children most at risk for dying.

Molecular cloning and biologically active production of IpaD N-terminal region

Shigella is known as pathogenic intestinal bacteria in high dispersion and pathogenic bacteria due to invasive plasmid antigen (Ipa). So far, a number of Ipa proteins have been studied to introduce a new candidate vaccine. Here, for the first time, we examined whether the N-terminal region of IpaD(72-162) could be a proper candidate for Shigella vaccine. Initially, the DNA sequence coding N-terminal region was isolated by PCR from Shigella dysenteriae type I and cloned into pET-28a expression vector. Then, the heterologous protein was expressed, optimized and purified by affinity Ni-NTA column. Western blot analysis using, His-tag and IpaD(72-162) polyclonal antibodies, confirmed the purity and specificity of the recombinant protein, respectively. Subsequently, the high immunogenicity of the antigen was shown by ELISA. The results of the sereny test in Guinea pigs showed that IpaD(72-162) provides a protective system against Shigella flexneri 5a and S. dysenteriae type I.

The antimicrobial effect of lactobacillus casei culture supernatant against multiple drug resistant clinical isolates of Shigella sonnei and Shigella flexneri in vitro

Backgrounds

Shigellosis remains an important public health problem in developing countries with S. sonnei and S. flexneri in US, Europe and in Asian countries being of importance.

Objectives

This study evaluates the protective effect of Lactobacillus casei cell-free culture supernatants (CFCS) against multiple drug resistance (MDR) clinical samples of Shigella sonnei and Shigella flexneri in vitro.

Materials and Methods

S. sonnei and S .flexneri was identified by common microbiological and serological methods. Antibiogram with 18 antibiotics were tested for 34 positive cultures by disc diffusion method. The Samples showed considerable resistance to antibiotics. Antimicrobial effects of CFCS were tested against S. sonnei and S. flexneri by agar-well assay and broth micro dilution methods. In addition, the antimicrobial activity remained active treatment after adjust pH 7, adding Proteinase K and heating for L. casei.

Results

The results implicate that L. casei strongly inhibits the development of pathogen samples. In contrast, via the disc diffusion method 4 out of 18 antibiogram have shown complete resistance against the pathogen samples. In addition, the natures of antimicrobial properties have been tested in different conditions such as various pH, temperature and presence of proteinase K. The MIC50 (minimum inhibitory concentration) and MIC90 of CFCS of L. casei were determined, for S. sonnei were 2.25 and 10.5, for S .flexneri were 5.25 and 5.25 respectively. The results have shown a significant resistance pattern by these four antibiotics in this case.

Conclusions

The data indicates that. L. casei highly resistant against to antibiotics, heat, Proteinase K and so many activities against MDR Shigella pathogenic strains . L. casei is the best probiotics candidate.

The microbiota link to irritable bowel syndrome: an emerging story

Irritable Bowel Syndrome (IBS) is a clinically heterogeneous disorder which is likely to involve a number of causative factors. The contribution of altered intestinal microbiota composition or function to this disorder is controversial, and is the subject of much current research. Until recently, the technical limitations of the methodologies available have not permitted an adequate survey of low-abundance microbial species. Recent technological developments have enabled the analysis of the global population of the microbiome using high through-put, culture independent, 16S rRNA amplicon pyrosequencing. Using these new methodologies, we are able to gain important biological insights into the link between functional bowel disorders and the microbiome. This addendum contextualizes and summarizes the results of these studies, and defines the future challenges and opportunities in the field.

Systemic shigellosis in South Africa

BACKGROUND

Systemic disease due to shigellae is associated with human immunodeficiency virus (HIV), malnutrition, and other immunosuppressed states. We examined the clinical and microbiologic characteristics of systemic shigellosis in South Africa, where rates of HIV infection are high.

METHODS

From 2003 to 2009, 429 cases of invasive shigellosis were identified through national laboratory-based surveillance. At selected sites, additional information was captured on HIV serostatus and outcome. Isolates were serotyped and antimicrobial susceptibility testing performed.

RESULTS

Most cases of systemic shigellosis were diagnosed on blood culture (408 of 429 cases; 95%). HIV prevalence was 67% (80 of 120 cases), highest in patients aged 5-54 years, and higher among females (55 of 70 cases; 79%) compared with males (25 of 48 cases; 52%; P = .002). HIV-infected people were 4.1 times more likely to die than HIV-uninfected cases (case-fatality ratio, 29 of 78 HIV-infected people [37%] vs 5 of 40 HIV-uninfected people [13%]; P = .008; 95% confidence interval [CI], 1.5-11.8). The commonest serotype was Shigella flexneri 2a (89 of 292 serotypes [30.5%]). Pentavalent resistance occurred in 120 of 292 isolates (41.1%). There was no difference in multidrug resistance between HIV-infected patients (33 of 71 [46%]) and uninfected patients (12 of 33 [36%]; 95% CI, .65--3.55).

CONCLUSIONS

Systemic shigellosis is associated with HIV-infected patients, primarily in older girls and women, potentially due to the burden of caring for sick children in the home; interventions need to be targeted here. Death rates are higher in HIV-infected versus uninfected individuals.

Genetics and environmental regulation of Shigella iron transport systems

Shigella spp. have transport systems for both ferric and ferrous iron. The iron can be taken up as free iron or complexed to a variety of carriers. All Shigella species have both the Feo and Sit systems for acquisition of ferrous iron, and all have at least one siderophore-mediated system for transport of ferric iron. Several of the transport systems, including Sit, Iuc/IutA (aerobactin synthesis and transport), Fec (ferric di-citrate uptake), and Shu (heme transport) are encoded within pathogenicity islands. The presence and the genomic locations of these islands vary considerably among the Shigella species, and even between isolates of the same species. The expression of the iron transport systems is influenced by the concentration of iron and by environmental conditions including the level of oxygen. ArcA and FNR regulate iron transport gene expression as a function of oxygen tension, with the sit and iuc promoters being highly expressed in aerobic conditions, while the feo ferrous iron transporter promoter is most active under anaerobic conditions. The effects of oxygen are also seen in infection of cultured cells by Shigella flexneri; the Sit and Iuc systems support plaque formation under aerobic conditions, whereas Feo allows plaque formation anaerobically.

Recent progress in understanding the phenotype and function of intestinal dendritic cells and macrophages

Mucosal immune responses must be tightly controlled, particularly in the intestine. As members of the mononuclear phagocyte family, dendritic cells (DCs) and macrophages are well represented in intestinal tissues and have developed unique functional niches. This review will focus on recent findings on antigen uptake and processing in the intestine and the role of DCs in the imprinting of homing receptors on T and B cells, the induction of immunoglobulin A B-cell responses, and the differentiation of regulatory T cells. It will also address the unique phenotype of intestinal macrophages and briefly what is known regarding the relationships between these cell types.