Total antioxidant capacity of plasma in asymptomatic carrier state of Neisseria meningitidis

Pathogenomic in silico approach identifies NSP-A and Fe-IIISBP as possible drug targets in Neisseria Meningitidis MC58 and development of pharmacophores as novel therapeutic candidates

Meningitis creates a life-threatening clinical crisis. Moreover, the administered antibiotics result into multi-drug resistance, thereby necessitating development of alternative therapeutic strategies. This study aimed at identifying novel-drug targets in Neisseria meningitidis and therapeutic molecules which can be exploited for the treatment of meningitis. Novel targets were identified by applying a pathogenomic approach involving protein data-set mining, subtractive channel analysis and subsequent qualitative analysis comprising of in silico pharmacokinetics, molecular docking and pharmacophore generation. Pathogenomic studies revealed Neisserial Surface Protein A (NSP-A) and Iron-III-Substrate Binding Protein (Fe-IIISBP) as potential targets. Two pharmacophore models comprising of 2-(biaryl) carbapenems, efavirenz, praziquantel and pyrimethamine for NSP-A and 2-(biaryl) carbapenems, trimipramine and pyrimethamine for Fe-IIISBP, showed successful docking, followed drug-likeness criteria and generated pharmacophore model with a score of 8.08 and 8.818, respectively, which had further been docked to the target stably. Thus, our study identifies NSP-A and Fe-IIISBP as novel targets in Neisseria meningitidis for which 2-(biaryl) carbapenems, efavirenz, praziquantel, trimipramine and pyrimethamine may be employed for effective treatment of meningitis.

Suppressed inflammation in obese children induced by a high-fiber diet is associated with the attenuation of gut microbial virulence factor genes

In our previous study, a gut microbiota-targeted dietary intervention with a high-fiber diet improved the immune status of both genetically obese (Prader-Willi Syndrome, PWS) and simple obese (SO) children. However, PWS children had higher inflammation levels than SO children throughout the trial, the gut microbiota of the two cohorts was similar. As some virulence factors (VFs) produced by the gut microbiota play a role in triggering host inflammation, this study compared the characteristics and changes of gut microbial VF genes of the two cohorts before and after the intervention using a fecal metagenomic dataset. We found that in both cohorts, the high-fiber diet reduced the abundance of VF, and particularly pathogen-specific, genes. The composition of VF genes was also modulated, especially for offensive and defensive VF genes. Furthermore, genes belonging to invasion, T3SS (type III secretion system), and adherence classes were suppressed. Co-occurrence network analysis detected VF gene clusters closely related to host inflammation in each cohort. Though these cohort-specific clusters varied in VF gene combinations and cascade reactions affecting inflammation, they mainly contained VFs belonging to iron uptake, T3SS, and invasion classes. The PWS group had a lower abundance of VF genes before the trial, which suggested that other factors could also be responsible for the increased inflammation in this cohort. This study provides insight into the modulation of VF gene structure in the gut microbiota by a high-fiber diet, with respect to reduced inflammation in obese children, and differences in VF genes between these two cohorts.

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background

The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented.

Objective

We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger.

Methods

We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice.

Results

High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis.

Conclusion

Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust.

Surface adhesion and host response as pathogenicity factors of Neisseria meningitidis

Neisseria meningitidis (N. meningitidis) is an exclusively human pathogen that has been identified in 10%-35% of the adult population and in 5.9% of the child population. Despite the high prevalence of carriers of N. meningitidis, it only occasionally causes meningococcal disease in the context of endemic disease, in certain geographic areas or in isolated epidemic outbreaks. After the N. meningitidis genome is described, progress has been made toward understanding the pathogenic mechanisms of the bacteria, although some aspects concerning its interaction with the environment and the host remain unclear. Some studies have reported that oxidative stress in the environment can modify the surface characteristics of N. meningitidis, increasing its adhesive properties and favouring an asymptomatic carrier state. The antigenic structure of N. meningitidis can be modified by its importing genetic material from other bacteria in its ecological niche. Some structures of lipopolysaccharides help it to evade the immune response, and these are observed more frequently in N. meningitidis isolated from blood than in healthy nasopharyngeal carriers. There is evidence that pili and capsule are downregulated upon contact with target cells. This paper reviews current knowledge on host-environment-bacteria mechanisms and interactions, with the aim of contributing to our understanding of the pathogenic mechanisms of N. meningitidis.

Overweight and obesity as risk factors for the asymptomatic carrier state of Neisseria meningitidis among a paediatric population

We analysed the asymptomatic carrier state of Neisseria meningitidis in a sample of 339 children. We obtained data for the children's weight and height, in order to calculate the body mass index (BMI). The cutoff points defined by Cole were employed in determining the BMI, and the population was divided into three groups: normal, overweight and obese. Twenty carriers of N. meningitidis were identified. There was found to be a statistically significant trend to increased risk of being a carrier with increased BMI (z=2.03; P=0.04); after adjusting for age using the Mantel-Haenszel weighting method, this relationship was strengthened (z=2.38; P=0.01). Paediatric patients with increased BMI in the range of obesity present a three times greater risk of being carriers of N. meningitidis than non-obese patients, with a trend for this risk to increase with higher BMI.

Efficient assay for total antioxidant capacity in human plasma using a 96-well microplate

In the present study, we tried to establish an efficient assay for total antioxidant capacity (TAC) in human plasma using a 96-well microplate. TAC was assessed using lag time by antioxidants against the myoglobin-induced oxidation of 2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) with hydrogen peroxide, and expressed as Trolox equivalent. The linearity of the calibration curve with Trolox was maintained with the Trolox concentration range from 2.5 µM to 25 µM (R² = 0.997). The assay was applied to the measurement of TAC in healthy human plasma. Coefficient of variation in intraday assay was 2.4%. Difference was not observed in interday assay. Plasma TAC of men ((569 ± 41) µM Trolox equivalent; n = 6) was higher than that of women ((430 ± 28) µM Trolox equivalent; n = 4). After the vegetable juice was drunk for 1 week, the increase in plasma TAC was observed in almost all the volunteers. In summary, we developed the efficient assay for plasma TAC using a 96-well microplate.