Tracking Vibrio cholerae Cell-Cell Interactions during Infection Reveals Bacterial Population Dynamics within Intestinal Microenvironments

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The Effects of Vaccination and Immunity on Bacterial Infection Dynamics In Vivo

Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body.     

Mucin Biopolymers Prevent Bacterial Aggregation by Retaining Cells in the Free-Swimming State

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Highlights? Mucin biopolymers reduce bacterial adhesion to underlying substrates ? Bacterial motility is maintained or increased in the presence of mucins ? Mucins block aggregate formation by motile bacteria ? Immotile Pseudomonas aeruginosa can form alginate and Psl-dependent flocs in mucus     

High Beta-Palmitate Fat Controls the Intestinal Inflammatory Response and Limits Intestinal Damage in Mucin Muc2 Deficient Mice

Background

Palmitic-acid esterified to the sn-1,3 positions of the glycerol backbone (alpha, alpha’-palmitate), the predominant palmitate conformation in regular infant formula fat, is poorly absorbed and might cause abdominal discomfort. In contrast, palmitic-acid esterified to the sn-2 position (beta-palmitate), the main palmitate conformation in human milk fat, is well absorbed. The aim of the present study was to examine the influence of high alpha, alpha’-palmitate fat (HAPF) diet and high beta-palmitate fat (HBPF) diet on colitis development in Muc2 deficient (Muc2^−/−) mice, a well-described animal model for spontaneous enterocolitis due to the lack of a protective mucus layer.

Methods

Muc2^−/− mice received AIN-93G reference diet, HAPF diet or HBPF diet for 5 weeks after weaning. Clinical symptoms, intestinal morphology and inflammation in the distal colon were analyzed.

Results

Both HBPF diet and AIN-93G diet limited the extent of intestinal erosions and morphological damage in Muc2^−/− mice compared with HAPF diet. In addition, the immunosuppressive regulatory T (Treg) cell response as demonstrated by the up-regulation of Foxp3, Tgfb1 and Ebi3 gene expression levels was enhanced by HBPF diet compared with AIN-93G and HAPF diets. HBPF diet also increased the gene expression of Pparg and enzymatic antioxidants (Sod1, Sod3 and Gpx1), genes all reported to be involved in promoting an immunosuppressive Treg cell response and to protect against colitis.

Conclusions

This study shows for the first time that HBPF diet limits the intestinal mucosal damage and controls the inflammatory response in Muc2^−/− mice by inducing an immunosuppressive Treg cell response.     

Dynamics of Bacterial Swarming

When vegetative bacteria that can swim are grown in a rich medium on an agar surface, they become multinucleate, elongate, synthesize large numbers of flagella, produce wetting agents, and move across the surface in coordinated packs: they swarm. We examined the motion of swarming Escherichia coli, comparing the motion of individual cells to their motion during swimming. Swarming cells' speeds are comparable to bulk swimming speeds, but very broadly distributed. Their speeds and orientations are correlated over a short distance (several cell lengths), but this correlation is not isotropic. We observe the swirling that is conspicuous in many swarming systems, probably due to increasingly long-lived correlations among cells that associate into groups. The normal run-tumble behavior seen in swimming chemotaxis is largely suppressed, instead, cells are continually reoriented by random jostling by their neighbors, randomizing their directions in a few tenths of a second. At the edge of the swarm, cells often pause, then swim back toward the center of the swarm or along its edge. Local alignment among cells, a necessary condition of many flocking theories, is accomplished by cell body collisions and/or short-range hydrodynamic interactions.     

Butyrate-Producing Bacteria,Including Mucin Degraders,from the Swine Intestinal Tract

To identify bacteria with potential for influencing gut health, 980 anaerobes were cultured from the swine intestinal tract and analyzed for butyrate production. Fifteen isolates in the order Clostridiales produced butyrate and had butyryl coenzyme A (CoA):acetate CoA transferase activity. Three of the isolates grew on mucin, suggesting an intimate association with host intestinal mucosa.     

子宫内膜与细菌L型感染

本文报道41例宫腔刮出物的病原微生物培养,其中子宫异常出血和早孕胎盘组织各15例,月经紊乱6例和不孕症5例。19例细菌培养为阳性(46.35),19例中之7例为细菌兼有 L 型感染,8例为单纯 L 型感染,3例为解脲脲原体和1例 G~ 厌氧球菌感染。L 型菌落呈典型“油煎蛋”样或颗粒样。子宫内膜和胎盘组织切片的细菌学检查发现大量 L 型巨形体、圆球体和长丝体。作者认为在妇产科范围内,细菌 L 型和解脲脲原体感染并非少见,可能是子宫异常出血、月经紊乱、不孕症和流产的重要原因之一。L 型的形成与抗生素治疗及体内因素的诱导有关。在治疗 L 型感染过程中,药物的选择很重要。     

Identification of Bacterial Infection in Neotropical Primates

Emerging infectious diseases usually arise from wild animal populations. In the present work, we performed a screening for bacterial infection in natural populations of New World primates. The blood cell bulk DNAs from 181 individuals of four Platyrrhini genera were PCR screened for eubacterial 16S rRNA genes. Bacteria were detected and identified in 13 distinct individuals of Alouatta belzebul, Alouatta caraya, and Cebus apella monkeys from geographically distant regions in the states of Mato Grosso and Pará, Brazil. Sequence analyses showed that these Platyrrhini bacteria are closely related not only to human pathogens Pseudomonas spp. but also to Pseudomonas simiae and sheep-Acari infecting Pseudomonas spp. The identified Pseudomonas possibly represents a group of bacteria circulating in natural monkey populations.     

Role of Mucin Lewis Status in Resistance to Helicobacter pylori Infection in Pediatric Patients

Background: Helicobacter pylori causes gastritis, peptic ulcer and is a risk factor for adenocarcinoma and lymphoma of the stomach. Gastric mucins, carrying highly diverse carbohydrate structures, present functional binding sites for H. pylori and may play a role in pathogenesis. However, little information is available regarding gastric mucin in children with and without stomach diseases. Materials and Methods: Expression of mucins and glycosylation was studied by immunohistochemistry on gastric biopsies from 51 children with and without H. pylori infection and/or peptic ulcer disease. Results: In all children, MUC5AC was present in the surface epithelium and MUC6 in the glands. No MUC6 in the surface epithelium or MUC2 was detected in any section. The Le^b and Le^a blood group antigens were present in the surface epithelium of 80% and 29% of children, respectively. H. pylori load was higher in Le^b negative children than in Le^b positive individuals (mean ± SEM 17.8 ± 3.5 vs 10.8 ± 1.5; p < 0.05), but there was no correlation between Le^a or Le^b status and gastritis, nodularity, and gastric or duodenal ulcer (DU). Expression of sialyl‐Le^x was associated with H. pylori infection, and DU. Conclusions: Mucin expression and glycosylation is similar in children and adults. However, in contrast to adults, pediatric H. pylori infection is not accompanied by aberrant expression of MUC6 or MUC2. Furthermore, the lower H. pylori density in Le^b positive children indicates that H. pylori is suppressed in the presence of gastric mucins decorated with Le^b, the binding site of the H. pylori BabA adhesin.     

肠道气泡堆积对银鲳肠道菌群结构的影响

为研究肠道气泡堆积对银鲳(Pampus argenteus)肠道菌群的影响,2019年3月于东海水产研究所福鼎研究中心采集了15尾肠道气泡堆积的银鲳为病鱼组,15尾健康银鲳为健康鱼组,并通过16S r DNA基因DNA高通量测序技术结合LEfSe分析方法,对两组样品间菌群结构和多样性进行对比分析。结果显示,病鱼组肠道菌群多样性与健康鱼组无显著差异(P> 0.05),但病鱼组肠道菌群的均匀度和相对丰度都显著低于健康鱼组(P <0.05)。两组样品的优势菌群均为变形菌门(Proteobacteria),且相对丰度都较大(超过97%)。此外,利用LEfSe分析两组样品发现,病鱼组中如根瘤菌(Rhizobium)、栖热菌(Thermus)等好氧菌丰度显著高于健康鱼组,而不动肝菌(Acinetobacter)、微酸菌(Ilumatobacter)等显著低于健康鱼组,蓝细菌(Cyanobacteria)相对丰度显著高于健康鱼组。由此可以表明,肠道气泡堆积很可能会引发肠道菌群紊乱。     

细菌L型感染与慢性子宫内膜炎

本文应用微生物培养、免疫组织化学等方法,对876例子宫内膜进行了组织病理学研究。发现:1.子宫内膜细菌 L 型感染病例中,32.5%的内膜间质有淋巴细胞浸润、淋巴滤泡形成或伴有浆细胞浸润。尚有部分病例虽有感染,但无慢性炎细胞浸润。2.细菌学检查阴性病例,内膜间质无慢性炎细胞浸润。3.病原微生物培养显示70.8%为金黄色葡萄球菌 L 型感染。4.免疫组织化学证明子宫内膜间质细菌型和 L 型的检出率高于腺体。作者提出子宫内膜间质中淋巴细胞浸润或淋巴滤泡形成系细菌 L 型感染的病变特征。故也是慢性子宫内膜炎的诊断依据。     

Upregulation of Intestinal Mucin Expression by the Probiotic Bacterium E. coli Nissle 1917

The probiotic E. coli Nissle 1917 (EcN) has been reported to have various health benefits; however, very little is known about their underlying mechanisms. In this regard, the present study aimed to elucidate the effect of the bacterium on mucin production by intestinal epithelial cells. Incubation of HT-29 cells with EcN lead to a contact time-dependent rise in mRNA levels of the MUC2, MUC3, MUC5AC, and MUC5A. The expression was markedly higher with MUC5AC gene. In most cases, MUC genes expression was more pronounced in polarized cells compared to non-polarized ones. In contrast to MUC3, the basal stimulation of polarized cells brought about markedly higher levels of other tested mucins. Similar but milder results were observed when living EcN was replaced by inactivated bacteria. With exception of MUC3, the conditioned media showed no significant effect on the mRNA level of the tested mucins. The above-mentioned mRNA results were confirmed on protein level using enzyme-linked lectin assay (ELLA) and enzyme-linked immunosorbant assay (ELISA). In contrast to other treatments, basal stimulation of polarized cells showed a growth phase-dependent MUC induction with more prominent effect by stationary-phase bacteria. In contrast to MUC 2 and MUC3, the induction of MUC5AC and MUC5B showed a bacterial count-dependent pattern. In conclusion, EcN was found to stimulate MUC gene expression in HT-29 intestinal cells. This stimulation was more distinct with polarized cells. Such observation may partially interpret some health benefits of the probiotic bacterium including antagonizing pathogen adhesion and protection of the intestinal mucosa.     

Intracellular Dynamics of HIV Infection

Early studies of HIV infection dynamics suggested that virus-producing HIV-infected cells had an average half-life of approximately 1 day. However, whether this average behavior is reflective of the dynamics of individual infected cells is unclear. Here, we use HIV-enhanced green fluorescent protein (EGFP) constructs and flow cytometry sorting to explore the dynamics of cell infection, viral protein production, and cell death in vitro. By following the numbers of productively infected cells expressing EGFP over time, we show that infected cell death slows down over time. Although infected cell death in vivo could be very different, our results suggest that the constant decay of cell numbers observed in vivo during antiretroviral treatment could reflect a balance of cell death and delayed viral protein production. We observe no correlation between viral protein production and death rate of productively infected cells, showing that viral protein production is not likely to be the sole determinant of the death of HIV-infected cells. Finally, we show that all observed features can be reproduced by a simple model in which infected cells have broad distributions of productive life spans, times to start viral protein production, and viral protein production rates. This broad spectrum of the level and timing of viral protein production provides new insights into the behavior and characteristics of HIV-infected cells.