Colonization Density Research Articles

Pneumococcal Serotypes Colonise the Nasopharynx in Children at Different Densities.

Prevalence of pneumococcal serotypes in carriage and disease has been described but absolute serotype colonisation densities have not been reported. 515 paediatric nasal swab DNA extracts were subjected to lytA qPCR and molecular serotyping by microarray. Absolute serotype densities were derived from total pneumococcal density (qPCR cycle threshold and standard curve) and relative abundance (microarray) and varied widely. Compared to all serotype densities observed, the strongest evidence of differences was seen for serotypes 21 and 35B (higher) and 3, 38 and non-typeables (lower) (p<0.05) with a similar hierarchy when only a single serotype carriage was assessed. There was no evidence of any overall density differences between children with single or multiple serotypes detected but serotypes with mid-range densities were more prevalent. The hierarchy of distinct pneumococcal serotype carriage densities described here for the first time, may help explain the dynamics of transmission between children.

Diversity and abundance of arbuscular mycorrhizal fungi under different plant and soil properties in Sidama, southern Ethiopia

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops may make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs) (villages within districts where 300–500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity and abundance of AMF under selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of AMF root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total AMF colonization was recorded for shade trees Millettia ferruginea (84 %) and Erythrina brucei (80 %) followed by intercropped perennial crops Ensete ventricosum (86 %), Catha edulis (85 %) and Coffea arabica (80 %) and the lowest percentage AMF colonization was recorded for Rhamnus prinoides (53 %) and Colocasia esculenta (52 %). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066 ± 19.33) and Catha edulis (1054 ± 53.12) and the lowest spore density was recorded for Dioscorea alata (100.00 ± 2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage AM root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P < 0.05 level.

Beneath the bark: associations among Sirex noctilio development, bluestain fungi, and pine host species in North America

1. Invasive species with global distributions encounter unique environmental and biotic variables that can greatly affect the magnitude of their impact. The European woodwasp, Sirex noctilio Fabricius, is a prime example that has invaded climatically and ecologically distinct ecosystems across the Southern Hemisphere and, more recently, North America.2. Northeastern North America presents a unique set of conditions, including pine host species, native parasitoids, a diverse assemblage of native co‐colonising insects, and fungal associates of these co‐colonisers. In North America, S. noctilio attacks both a naturalised ancestral host (Pinus sylvestris L.) from Europe and a naïve native host (P. resinosa). A large assemblage of insects and their associated bluestaining ophiostomatoid fungi colonise these pines. Competition between S. noctilio and this group is a hypothesised mechanism of biotic resistance in the invaded region of North America, possibly via superior resource capture abilities or alteration of host tissue by bluestain fungi.3. Investigating these ecological interactions is challenging because they manifest deep in the xylem tissue. To overcome this, 30 experimentally stressed trees were systematically dissected with an electric log splitter to investigate the effects of bluestain fungi and tree factors on S. noctilio development and parasitism by native hymenopterans.4. Body size and colonisation density were affected by pine species, with S. noctilio being 25% larger and densities three‐fold greater in P. sylvestris than P. resinosa. Survivorship was slightly negatively correlated with the proportional volume of bluestain infection. Interestingly, rhyssine (Rhyssa and Megarhyssa spp.) parasitism responded positively to greater S. noctilio density, but there was no density relationship with Ibalia leucospoides ensiger parasitism. Pine host species appears to play a strong role in S. noctilio development, which is important considering uninvaded regions of North America have a diversity of pine species that likely vary in their susceptibility to this woodborer.

Density, Serotype Diversity, and Fitness of Streptococcus pneumoniae in Upper Respiratory Tract Cocolonization With Nontypeable Haemophilus influenzae.

Coinfections by Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) are frequently implicated in complex otitis media. Whereas upper respiratory tract carriage precedes disease for both pathogens, interactions between species in cocolonized hosts are poorly understood. We compared colonization densities and the diversity and fitness of pneumococcal serotypes in single-species and mixed-species colonization. We analyzed nasopharyngeal pneumococcal carriage and nasopharyngeal and oropharyngeal NTHi carriage in 13 541 samples collected over 6909 study visits from 769 children 2-30 months old in a 7-valent pneumococcal conjugate vaccine dosing trial. We measured density associations between the species and compared pneumococcal serotype diversity during and in the absence of NTHi colonization. We used logistic regression to quantify associations between NTHi colonization and previously published pneumococcal serotype factors related to fitness. Densities of the 2 species were positively associated when they co-occur in the nasopharynx. NTHi colonization was associated with reduced pneumococcal serotype diversity among children 2-18 months old and was more prevalent among children carrying pneumococcal serotypes with greater capsular thickness, neutrophil resistance, and metabolic efficiency. Pneumococcal-NTHi cocolonization is associated with an elevated density of both species and with reduced diversity and increased fitness of pneumococcal serotypes. NTHi colonization may create a selective environment favoring pneumococci with immune-evasive phenotypes.

English

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs) (villages within districts where 300 to 500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity of AMF based on selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total colonization was recorded for shade trees Millettia ferruginea (84%) and Erythrina brucei (80%) followed by intercropped perennial crops Ensete ventricosum (86%), Catha edulis (85%) and Coffea arabica (80%) and the lowest percentage colonization was recorded for Rhamnus prinoides (53%) and Colocasia esculenta (52%). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066±19.33) and Catha edulis (1054±53.12) and the lowest spore density was recorded for Dioscorea alata (100.00±2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P<0.05 level. Key words: Arbuscular mycorrhizal fungi (AMF), dependency, rhizosphere, parameters, colonization, density.

Effect of 4% chlorhexidine on cord colonization among hospital and community births in India: a randomized controlled study.

BackgroundInfections are the single most important cause of neonatal mortality in developing countries. Results from trials in Asia evaluating the effect of chlorhexidine on neonatal mortality have been encouraging but limited data are available on the impact of cord cleansing on bacterial colonization. Further, no data from facility deliveries and impact with time is available. This pilot study was aimed to evaluate the impact of 4 % commercially prepared chlorhexidine on cord colonization and density of colonization among newborns in India.MethodsThree hundred twenty-six newborns (hospital-247; community-79) were enrolled within 24 h of birth and randomly assigned to one of three groups: chlorhexidine, placebo or dry cord care. Umbilical swabs were collected at baseline, 2- and 48- hours after intervention application.ResultsAt baseline, growth positivity (any bacterial growth) was 20 % (50 of 247 swabs) and 81 % (64 of 79 swabs) among hospital and community born neonates, respectively. In both settings, chlorhexidine compared to placebo and dry cord care, reduced colonization following 2- and 48-hour post application. Chlorhexidine significantly reduced 48-hour post application colony counts in comparison to placebo [Hospital: mean difference = −1.01; 95 % CI: −1.72, −0.30 Community: mean difference = −1.76; 95 % CI: −2.60, −0.93] and dry cord care [Hospital: mean difference = −1.16; 95 % CI: −1.93, −0.39 Community: mean difference = −2.23; 95 % CI: −3.18, −1.29]. Differences were similar for gram-positive and gram-negative bacteria.ConclusionsCord cleansing with 4 % chlorhexidine soon after birth reduced colonization as well as density of colonization significantly; however this pilot study does not address the impact of chlorhexidine on mortality. The control preparation neither increased or decreased colonization.Trial registrationClinical Trial Registration: clinicaltrials.gov: NCT01528852, Registered February 7, 2012. Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-016-0625-7) contains supplementary material, which is available to authorized users.

Prophylactic herbal therapy prevents experimental ascending urinary tract infection in mice.

To study the preventive effect of herbal formulation on experimental murine urinary tract infection (UTI) induced by Dr Escherichia coli 11128. E. coli 11128 carrying Dr fimbriae was isolated from patients with chronic pyelonephritis. The minimal inhibitory concentration (MIC) value of herbal solution for E. coli 11128 was determined for further studies. Forty C3H/HeJ mice were divided into the herb-treated group (n=20, given Chinese herbs by gavage at an average dose of 20 g/kg body weight daily 3 days before inoculation), and control group (n=20, given the same amount of distilled water by gavage). Three and 6 days after infection, bacteria were counted in the urine and the kidneys of the mice. Kidney histopathologic changes were evaluated. Neutrophils infiltration and accumulation were detected. The MIC value of herbal solution was 0.1 g/mL for the E. coli 11128. In herb-treated mice, there was a significant reduction in bacterial counts in urine and colonization densities of kidneys. Microscopic studies revealed signs of inflammation in kidneys. In herb-treated mice, herbal administration resulted in significantly reduced neutrophilic infiltrates (P<0.05). The semi-quantitative scores for renal lesions were significantly lower (P<0.05). Prophylactic administration of herbal formulation potentiated the effect in partially preventing experimental murine ascending UTI.

Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection.

One of the least understood aspects of the bacterium Streptococcus pneumoniae (pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, shedding, and transmission during bacterial monoinfection. Using this model, we demonstrated that the level of bacterial shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized "index" pups to uncolonized "contact" pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of shedding. This model can be used to examine bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.

Staphylococcus aureus colonization related to severity of hand eczema.

Knowledge on Staphylococcus aureus colonization rates and epidemiology in hand eczema is limited. The aim of this study was to clarify some of these issues. Samples were collected by the "glove juice" method from the hands of 59 patients with chronic hand eczema and 24 healthy individuals. Swab samples were taken from anterior nares and throat from 43 of the 59 patients and all healthy individuals. S. aureus were spa typed and analysed by DNA-microarray-based genotyping. The extent of the eczema was evaluated by the hand eczema extent score (HEES). The colonization rate was higher on the hands of hand eczema patients (69%) compared to healthy individuals (21%, p < 0.001). This was also seen for bacterial density (p = 0.002). Patients with severe hand eczema (HEES ≥ 13) had a significantly higher S. aureus density on their hands compared to those with milder eczema (HEES = 1 to 12, p = 0.004). There was no difference between patients and healthy individuals regarding colonization rates in anterior nares or throat. spa typing and DNA-microarray-based genotyping indicated certain types more prone to colonize eczematous skin. Simultaneous colonization, in one individual, with S. aureus of different types, was identified in 60-85% of the study subjects. The colonization rate and density indicate a need for effective treatment of eczema and may have an impact on infection control in healthcare.

Helicobacter pylori promotes angiogenesis depending on Wnt/beta-catenin-mediated vascular endothelial growth factor via the cyclooxygenase-2 pathway in gastric cancer.

BackgroundHelicobacter pylori is an important pathogenic factor in gastric carcinogenesis. Angiogenesis (i.e., the growth of new blood vessels) is closely associated with the incidence and development of gastric cancer. Our previous study found that COX-2 stimulates gastric cancer cells to induce expression of the angiogenic growth factor VEGF through an unknown mechanism. Therefore, the aim of this study was to clarify the role of angiogenesis in H. pylori-induced gastric cancer development.MethodsTo clarify the relationship between H. pylori infection and angiogenesis, we first investigated H. pylori colonization, COX-2, VEGF, beta-catenin expression, and microvessel density (MVD) in gastric cancer tissues from 106 patients. In addition, COX-2, phospho-beta-catenin, and beta-catenin expression were measured by western blotting, and VEGF expression was measured by ELISA in H. pylori-infected SGC7901 and MKN45 human gastric cancer cells.ResultsH. pylori colonization occurred in 36.8 % of gastric carcinoma samples. Furthermore, COX-2, beta-catenin, and VEGF expression, and MVD were significantly higher in H. pylori-positive gastric cancer tissues than in H. pylori-negative gastric cancer tissues (P < 0.01). H. pylori infection was not related to sex or age in gastric cancer patients, but correlated with the depth of tumor invasion, lymph node metastasis, and tumor–node–metastasis stage (P < 0.05) and correlated with the COX-2 expression and beta-catenin expression(P < 0.01). Further cell experiments confirmed that H. pylori infection upregulated VEGF in vitro. Further analysis revealed that H. pylori-induced VEGF expression was mediated by COX-2 via activation of the Wnt/beta-catenin pathway.ConclusionsThe COX-2/Wnt/beta-catenin/VEGF pathway plays an important role in H. pylori-associated gastric cancer development. The COX-2/Wnt/beta-catenin pathway is therefore a novel therapeutic target for H. pylori-associated gastric cancers.

Antigen-Independent Restriction of Pneumococcal Density by Mucosal Adjuvant Cholera Toxin Subunit B.

For many bacterial respiratory infections, development of (severe) disease is preceded by asymptomatic colonization of the upper airways. For Streptococcus pneumoniae, the transition to severe lower respiratory tract infection is associated with an increase in nasopharyngeal colonization density. Insight into how the mucosal immune system restricts colonization may provide new strategies to prevent clinical symptoms. Several studies have provided indirect evidence that the mucosal adjuvant cholera toxin subunit B (CTB) may confer nonspecific protection against respiratory infections. Here, we show that CTB reduces the pneumococcal load in the nasopharynx, which required activation of the caspase-1/11 inflammasome, mucosal T cells, and macrophages. Our findings suggest that CTB-dependent activation of the local innate response synergizes with noncognate T cells to restrict bacterial load. Our study not only provides insight into the immunological components required for containment and clearance of pneumococcal carriage, but also highlights an important yet often understudied aspect of adjuvants.

Dispersal variability and associated population-level consequences in tree-killing bark beetles.

BackgroundDispersal is a key process in the response of insect populations to rapidly changing environmental conditions. Variability among individuals, regarding the timing of dispersal initiation and travelled distance from source, is assumed to contribute to increased population success through risk spreading. However, experiments are often limited in studying complex dispersal interactions over space and time. By applying a local-scaled individual-based simulation model we studied dispersal and emerging infestation patterns in a host − bark beetle system (Picea abies – Ips typgraphus). More specifically, we (i) investigated the effect of individual variability in beetle physiology (flight capacity) and environmental heterogeneity (host susceptibility level) on population-level dispersal success, and (ii) elucidated patterns of spatial and/or temporal variability in individual dispersal success, host selectivity, and the resulting beetle density within colonized hosts in differently susceptible environments.ResultsIndividual variability in flight capacity of bark beetles causes predominantly positive effects on population-level dispersal success, yet these effects are strongly environment-dependent: Variability is most beneficial in purely resistant habitats, while positive effects are less pronounced in purely susceptible habitats, and largely absent in habitats where host susceptibility is spatially scattered. Despite success rates being highest in purely susceptible habitats, scattered host susceptibility appeared most suitable for dispersing bark beetle populations as it ensures population spread without drastically reducing success rates. At the individual level, dispersal success generally decreases with distance to source and is lowest in early flight cohorts, while host selectivity increased and colonization density decreased with increasing distance across all environments.ConclusionsOur modelling approach is demonstrated to be a powerful tool for studying movement ecology in bark beetles. Dispersal variability largely contributes to risk spreading among individuals, and facilitates the response of populations to changing environmental conditions. Higher mortality risk suffered by a small part of the dispersing population (long-distance dispersers, pioneers) is likely paid off by reduced deferred costs resulting in fitness benefits for subsequent generations. Both, dispersal variability in space and time, and environmental heterogeneity are characterized as key features which require particular emphasis when investigating dispersal and infestation patterns in tree-killing bark beetles.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-016-0074-9) contains supplementary material, which is available to authorized users.

The Increasing Challenge of Multidrug-Resistant Gram-Negative Bacilli: Results of a 5-Year Active Surveillance Program in a Neonatal Intensive Care Unit.

Colonization and infection by multidrug-resistant gram-negative bacilli (MDR GNB) in neonatal intensive care units (NICUs) are increasingly reported.We conducted a 5-year prospective cohort surveillance study in a tertiary NICU of the hospital “Paolo Giaccone,” Palermo, Italy. Our objectives were to describe incidence and trends of MDR GNB colonization and the characteristics of the most prevalent organisms and to identify the risk factors for colonization. Demographic, clinical, and microbiological data were prospectively collected. Active surveillance cultures (ASCs) were obtained weekly. Clusters of colonization by extended spectrum β-lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae were analyzed by conventional and molecular epidemiological tools.During the study period, 1152 infants were enrolled in the study. Prevalences of colonization by MDR GNB, ESBL-producing GNB and multiple species/genera averaged, respectively, 28.8%, 11.7%, and 3.7%. Prevalence and incidence density of colonization by MDR GNB and ESBL-producing GNB showed an upward trend through the surveillance period. Rates of ESBL-producing E coli and K pneumoniae colonization showed wide fluctuations peaking over the last 2 years. The only independent variables associated with colonization by MDR GNB and ESBL-producing organisms and multiple colonization were, respectively, the days of NICU stay (odds ratio [OR] 1.041), the days of exposure to ampicillin–sulbactam (OR 1.040), and the days of formula feeding (OR 1.031). Most clusters of E coli and K pneumoniae colonization were associated with different lineages. Ten out of 12 clusters had an outborn infant as their index case.Our study confirms that MDR GNB are an increasing challenge to NICUs. The universal once-a-week approach allowed us to understand the epidemiology of MDR GNB, to timely detect new clones and institute contact precautions, and to assess risk factors. Collection of these data can be an important tool to optimize antimicrobials use and control the emergence and dissemination of resistances in NICU.

Diversity and Abundance of Arbuscular Mycorrhizal Fungi Under Different Plant and Soil Properties in Sidama, Southern Ethiopia

In Sidama, agroforestry represents land-use systems with deliberate management of multipurpose trees and shrubs that grow in intimate association with annual and perennial agricultural crops and/or livestock. The interaction of microbiota with the trees, shrubs and crops make the system fertile, productive and sustainable. One of the beneficial microbiota which has symbiotic association with most of the plants in agroforestry is arbuscular mycorrhizal fungi (AMF). In November and December of 2012, root and rhizosphere soil samples of 21 plant species from nine peasant associations (PAs)(villages within districts where 300-500 families live) were collected from the agroforestry practices in Sidama of Southern Ethiopia for the determination of diversity and abundance of AMF under selected soil parameters and plant species density. Findings on the diversity of AMF based on soil properties showed that at moderate to low P and N concentrations the rate of AMF root colonization and spore density was high in comparison with the rhizosphere soils with the highest P and N concentration. The highest percentage of total AMF colonization was recorded for shade trees Millettia ferruginea (84%) and Erythrina brucei (80%) followed by intercropped perennial crops Ensete ventricosum (86%), Catha edulis (85%) and Coffea arabica (80%) and the lowest percentage AMF colonization was recorded for Rhamnus prinoides (53%) and Colocasia esculenta (52%). Though found in almost all homegarden agroforestry practices and with broad coverage in Sidama agroforestry, some crops and vegetables such Brassica integrifolia and Cucurbita pepo, grown intercropped were found to be non-mycorrrhizal as none of the AMF structures were recorded. The highest number of AM spore population was recorded in rhizosphere soils of Croton macrostachyus (1066±19.33) and Catha edulis (1054±53.12) and the lowest spore density was recorded for Dioscorea alata (100.00±2.89) spore per 100 g of dry soil. The percentage fungal colonization in any individual plant species and spore population in the rhizosphere soils of that species did not correlate to each other and percentage AM root colonization and spore density of all plants in the agroforestry of Sidama were found significantly different at P<0.05 level.

Reproductive strategy of the invasive green mussel may result in increased competition with native fauna in the southeastern United States

Understanding the population dynamics of invasive species, such as the green mussel Perna viridis (Linnaeus, 1758), can aid in explaining the success of newly introduced populations and help predict the potential for spread. During a two-year field study of established populations in the invaded region of southwest Florida, year round gametogenesis and continuous spawning capabilities were observed through histological analysis of mussels collected monthly. This was supported by overall stable energetic reserves as measured through proximal biochemical composition (protein, glycogen and lipid content). However, egg outputs in the summer (6.4 × 10 6 ± 2.6 × 10 6 eggs / female) were significantly higher than egg outputs of winter-spawned mussels (7.7 × 10 4 ± 1.4 × 10 4 eggs / female). Stability in biochemical composition, suggests temperature and food availability were sufficient year round, allowing for the maintenance of reserves and active gametogenesis. Protein ranged from 409.0–628.0 mg g −1 , glycogen from 44.3–158.5 mg g −1 and total lipids from 7.4–13.5 mg g −1. Year-round reproductive capabilities supported by sufficient energy reserves may help explain the rapid colonization and high densities of green mussels along the southeastern United States and suggests the potential for competition with native species, particularly the eastern oyster Crassostrea virginica (Gmelin, 1791).

Influence of salinity on the development of the banana colonised by arbuscular mycorrhizal fungi

This study evaluated the effect of salt stress on the growth of banana seedling colonized with mycorrhizal fungi (AMF) on a substrate from a Quartzipsamment. The experiment was conducted in a greenhouse, using a completely randomized design in split plots; the plots had 5 levels of salinity in irrigation water (0.5, 1.5, 2.5, 3.5 and 4 5 dS m-1) and the subplots of four collection periods (40, 60, 80 and 100 days after transplanting), with 4 repetitions, totaling 80 experimental units. The seedlings of banana cv. Prata was produced by micropropagation and inoculated with arbuscular mycorrhizal and acclimatization for 40 days. Evaluations were made of leaf gas exchange, shoot dry mass, nutrient content, mycorrhizal root colonization and spore density. Increased levels of salinity caused reduction in dry matter production and photosynthetic rate, which may be associated with osmotic effects of salts in the soil, the increase in sodium and reduced the levels of N in leaves. Salinity reduced root mycorrhizal colonization, but did not influence the density of AMF spores under the conditions of this study.

Response of Arbuscular Mycorrhizal Fungi to Simulated Climate Changes by Reciprocal Translocation in Tibetan Plateau

Arbuscular mycorrhiza (AM) fungi are considered as an important factor in predicting plants and ecosystem responses to climate changes on a global scale. The Tibetan Plateau is the highest region on Earth with abundant natural resources and one of the most sensitive region to climate changes. To evaluate the complex response of arbuscular mycorrhizal fungi colonization and spore density to climate changes, a reciprocal translocation experiment was employed in Tibetan Plateau. The reciprocal translocation of quadrats to AM colonization and spore density were dynamic. Mycorrhizal colonization frequency presented contrary changed trend with elevations of quadrat translocation. Colonization frequency reduced or increased in majority quadrats translocated from low to high or from high to low elevation. Responses of colonization intensity to translocation of quadrats were more sensitive than colonization frequency. Arbuscular colonization showed inconsistent trend in increased or decreased quadrat. Vesicle colonization decreased with changed of quadrat from low to high elevations. However, no significant trend was observed. Although spore density was dynamic with signs of decreasing or increasing in translocated quadrats, the majority enhanced and declined respectively in descent and ascent quadrat treatments. It is crucial to understand the interactions between AM fungi and prairie grasses to accurately predict effects of climate change on these diverse and sensitive ecosystems. This study provided an opportunity for understanding the effect of climate changes on AM fungi.

Standardized Escherichia coli O157:H7 Exposure Studies in Cattle Provide Evidence that Bovine Factors Do Not Drive Increased Summertime Colonization.

The increased summertime prevalence of cattle carriage of enterohemorrhagic Shiga toxin-producing Escherichia coli O157:H7 (STEC O157) is associated with the increased summertime incidence of human infection. The mechanism driving the seasonality of STEC O157 carriage among cattle is unknown. We conducted experimental challenge trials to distinguish whether factors extrinsic or intrinsic to cattle underlie the seasonality of STEC O157 colonization. Holstein steers (n = 20) exposed to ambient environmental conditions were challenged with a standardized pool of STEC O157 strains four times at 6-month intervals. The densities and durations of rectoanal junction mucosa (RAJ) colonization with STEC O157 were compared by season (winter versus summer), dose (10(9) CFU versus 10(7) CFU), and route of challenge (oral versus rectal). Following summer challenges, the RAJ STEC O157 colonization density was significantly lower (P = 0.016) and the duration was shorter (P = 0.052) than for winter challenges, a seasonal pattern opposite to that observed naturally. Colonization was unaffected by the challenge route, indicating that passage through the gastrointestinal microbiome did not significantly affect the infectious dose to the RAJ. A 2-log reduction of the challenge doses in the second-year trials was accompanied by similarly reduced RAJ colonization in both seasons (P < 0.001). These results refute the hypothesis that cattle are predisposed to STEC O157 colonization during the summer months, either due to intrinsic factors or indirectly due to gastrointestinal tract microbiome effects. Instead, the data support the hypothesis that the increased summertime STEC O157 colonization results from increased seasonal oral exposure to this pathogen.

First human challenge testing of a pneumococcal vaccine. Double-blind randomized controlled trial.

New vaccines are urgently needed to protect the vulnerable from bacterial pneumonia. Clinical trials of pneumonia vaccines are slow and costly, requiring tens of thousands of patients. Studies of pneumococcal vaccine efficacy against colonization have been proposed as a novel method to down-select between vaccine candidates. Using our safe and reproducible experimental human pneumococcal colonization model, we aimed to determine the effect of 13-valent pneumococcal conjugate vaccine (PCV) on colonization. A total of 100 healthy participants aged 18-50 years were recruited into this double-blind randomized placebo-controlled trial. They were randomly assigned to PCV (n = 49) or hepatitis A (control, n = 50) vaccination and inoculated with 80,000 CFU/100 μl of Streptococcus pneumoniae (6B) per naris. Participants were followed up for 21 days to determine pneumococcal colonization by culture of nasal wash. The PCV group had a significantly reduced rate of 6B colonization (10% [5 of 48]) compared with control subjects (48% [23 of 48]) (risk ratio, 0.22; confidence interval, 0.09-0.52; P < 0.001). Density of colonization was reduced in the PCV group compared with the control group following inoculation. The area under the curve (density vs. day) was significantly reduced in the PCV compared with control group (geometric mean, 259 vs. 11,183; P = 0.017). PCV reduced pneumococcal colonization rate, density, and duration in healthy adults. The experimental human pneumococcal colonization model is a safe, cost-effective, and efficient method to determine the protective efficacy of new vaccines on pneumococcal colonization; PCV provides a gold standard against which to test these novel vaccines. Clinical trial registered with 45340436.

Diagnostic methods for H. pylori infection: Choices, opportunities and pitfalls.

Diagnostic methods for H. pylori infection: Choices, opportunities and pitfalls.