Current distribution of a pyrethroid resistance gene (kdr) in Anopheles gambiae complex from west Africa and further evidence for reproductive isolation of the Mopti form

In the field, the kdr mutation, involved in pyrethroid resistance, has been found widely distributed in the Savanna form of Anopheles gambiae s.s., but never in wild populations of the Mopti form or An. arabiensis, even in areas where both occur in sympatry with resistant Savanna populations. Under laboratory conditions, Mopti and Savanna forms were fully able to interbreed and the kdr mutation was transmissible from one form to the other. Both forms appeared to be exposed to pyrethroid selection pressure in the field. The absence of the kdr mutation in the Mopti form and the total lack of Mopti-Savanna heterozygotes in field populations provides further evidence of a pre-copulatory barrier to gene flow between these two forms. Molecular markers, including kdr, are powerful tools for studying population genetics and circulation of resistance genes, and should be used through an integrated approach for a better understanding of the speciation process.     

A surface acoustic wave sensor functionalized with a polypyrrole molecularly imprinted polymer for selective dopamine detection

A surface acoustic wave sensor operating at 104 MHz and functionalized with a polypyrrole molecularly imprinted polymer has been designed for selective detection of dopamine (DA). Optimization of pyrrole/DA ratio, polymerization and immersion times permitted to obtain a highly selective sensor, which has a sensitivity of 0.55°/mM (≈550 Hz/mM) and a detection limit of ≈ 10 nM. Morphology and related roughness parameters of molecularly imprinted polymer surfaces, before and after extraction of DA, as well as that of the non imprinted polymer were characterized by atomic force microscopy. The developed chemosensor selectively recognized dopamine over the structurally similar compound 4‐hydroxyphenethylamine (referred as tyramine), or ascorbic acid,which co‐exists with DA in body fluids at a much higher concentration. Selectivity tests were also carried out with dihydroxybenzene, for which an unexpected phase variation of order of 75% of the DA one was observed. Quantum chemical calculations, based on the density functional theory, were carried out to determine the nature of interactions between each analyte and the PPy matrix and the DA imprinted PPy polypyrrole sensing layer in order to account for the important phase variation observed during dihydroxybenzene injection. Copyright © 2015 John Wiley & Sons, Ltd.     

Emergence of epidemic Neisseria meningitidis serogroup X meningitis in Togo and Burkina Faso

Serogroup X meningococci (NmX) historically have caused sporadic and clustered meningitis cases in sub-Saharan Africa. To study recent NmX epidemiology, we analyzed data from population-based, sentinel and passive surveillance, and outbreak investigations of bacterial meningitis in Togo and Burkina Faso during 2006-2010. Cerebrospinal fluid specimens were analyzed by PCR. In Togo during 2006-2009, NmX accounted for 16% of the 702 confirmed bacterial meningitis cases. Kozah district experienced an NmX outbreak in March 2007 with an NmX seasonal cumulative incidence of 33/100,000. In Burkina Faso during 2007-2010, NmX accounted for 7% of the 778 confirmed bacterial meningitis cases, with an increase from 2009 to 2010 (4% to 35% of all confirmed cases, respectively). In 2010, NmX epidemics occurred in northern and central regions of Burkina Faso; the highest district cumulative incidence of NmX was estimated as 130/100,000 during March-April. Although limited to a few districts, we have documented NmX meningitis epidemics occurring with a seasonal incidence previously only reported in the meningitis belt for NmW135 and NmA, which argues for development of an NmX vaccine.     

Pneumococci in the African Meningitis Belt: Meningitis Incidence and Carriage Prevalence in Children and Adults

Background

The development of optimal vaccination strategies for pneumococcal conjugate vaccines requires serotype-specific data on disease incidence and carriage prevalence. This information is lacking for the African meningitis belt.

Methods

We conducted hospital-based surveillance of acute bacterial meningitis in an urban and rural population of Burkina Faso during 2007–09. Cerebrospinal fluid was evaluated by polymerase chain reaction for species and serotype. In 2008, nasopharyngeal swabs were obtained from a representative population sample (1 month to 39 years; N = 519) and additional oropharyngeal swabs from 145 participants. Swabs were evaluated by culture.

Results

Annual pneumococcal meningitis incidence rates were highest among <6-month-old (58/100,000) and 15- to 19-year-old persons (15/100,000). Annual serotype 1 incidence was around 5/100,000 in all age groups. Pneumococcal carriage prevalence in nasopharyngeal swabs was 63% among <5-year-old children and 22% among ≥5-year-old persons, but adding oropharyngeal to nasopharyngeal swabs increased the estimated carriage prevalence by 60%. Serotype 1 showed high propensity for invasive disease, particularly among persons aged ≥5 years.

Conclusions

Serotype 1 causes the majority of cases with a relatively constant age-specific incidence. Pneumococcal carriage is common in all age groups including adults. Vaccination programs in this region may need to include older target age groups for optimal impact on disease burden.     

Statins (HMG-coenzyme A reductase inhibitors)-biomimetic membrane binding mechanism investigated by molecular chromatography

Many studies have demonstrated that the statin beneficial effects on cardiovascular diseases like coronary are linked to their hypocholesterolemic properties. These lipid-lowering drugs are the first-line pharmacologic therapy for hypercholesterolemia. In this paper, the interaction of a series of statin molecules STCOOH (pravastatin (prava), mevastatin (meva), simvastatin (simva) and fluvastatin (fluva)) with a phosphatidylcholine monolayer immobilized on to porous silica particles has been studied using a biochromatographic approach (molecular chromatography). The immobilized artificial membrane (IAM) provided a biophysical model system to study the binding of the statin molecules to a lipid membrane. For all the test statin molecules, linear retention plots were observed at all temperatures. An analysis of the thermodynamics (i.e., enthalpy (DeltaH(0)), entropy (DeltaS(0)*)) of the interaction of the statin molecules with the immobilized monolayer was also carried out. The DeltaH(0) and DeltaS(0)* values were negative due to van der Waals interactions and hydrogen bonding between the statin molecules with the polar head groups of the phospholipid monolayer (polar retention effect). The statin elution order was: Prava相似文献   

Reducing the Time Requirement of k-Means Algorithm

Traditional k-means and most k-means variants are still computationally expensive for large datasets, such as microarray data, which have large datasets with large dimension size d. In k-means clustering, we are given a set of n data points in d-dimensional space R^d and an integer k. The problem is to determine a set of k points in R^d, called centers, so as to minimize the mean squared distance from each data point to its nearest center. In this work, we develop a novel k-means algorithm, which is simple but more efficient than the traditional k-means and the recent enhanced k-means. Our new algorithm is based on the recently established relationship between principal component analysis and the k-means clustering. We provided the correctness proof for this algorithm. Results obtained from testing the algorithm on three biological data and six non-biological data (three of these data are real, while the other three are simulated) also indicate that our algorithm is empirically faster than other known k-means algorithms. We assessed the quality of our algorithm clusters against the clusters of a known structure using the Hubert-Arabie Adjusted Rand index (ARI_HA). We found that when k is close to d, the quality is good (ARI_HA>0.8) and when k is not close to d, the quality of our new k-means algorithm is excellent (ARI_HA>0.9). In this paper, emphases are on the reduction of the time requirement of the k-means algorithm and its application to microarray data due to the desire to create a tool for clustering and malaria research. However, the new clustering algorithm can be used for other clustering needs as long as an appropriate measure of distance between the centroids and the members is used. This has been demonstrated in this work on six non-biological data.     

Wolbachia strain wAlbB shows favourable characteristics for dengue control use in Aedes aegypti from Burkina Faso

Dengue represents an increasing public health burden worldwide. In Africa, underreporting and misdiagnosis often mask its true epidemiology, and dengue is likely to be both more widespread than reported data suggest and increasing in incidence and distribution. Wolbachia-based dengue control is underway in Asia and the Americas but has not to date been deployed in Africa. Due to the genetic heterogeneity of African Aedes aegypti populations and the complexity of the host-symbiont interactions, characterization of key parameters of Wolbachia-carrying mosquitoes is paramount for determining the potential of the system as a control tool for dengue in Africa. The wAlbB Wolbachia strain was stably introduced into an African Ae. aegypti population by introgression, and showed high intracellular density in whole bodies and different mosquito tissues; high intracellular density was also maintained following larval rearing at high temperatures. No effect on the adult lifespan induced by Wolbachia presence was detected. Moreover, the ability of this strain to strongly inhibit DENV-2 dissemination and transmission in the host was also demonstrated in the African background. Our findings suggest the potential of harnessing Wolbachia for dengue control for African populations of Ae. aegypti.     

Comparison of macrofauna communities in sediments of the beds of vertical flow constructed wetlands planted with Panicum maximum (Jacq.) treating domestic wastewater

To improve our understanding of the ecological functioning of constructed wetlands, the macrofauna structure in the sediments of a constructed wetland planted with Panicum maximum treating domestic wastewater was studied. Two beds were planted with young P. maximum and two unplanted beds were used as controls. After 150 days of wastewater treatment on the beds, macrofauna was collected by taking five cores of sediment samples at the corners and the centre of each bed following three layers in the vertical profile. Globally, the planted beds removed COD, NH₄⁺, and PO₄^3? more (p < 0.05) than the control. Eleven taxa belonging to 6 classes and 11 orders were recorded. Macrofauna was significantly more diversified (Mann–Whitney test: p < 0.05) in terms of Shannon index of diversity in the planted beds (0.25–0.44 bits/ind.) than in the control (0.08–0.23 bits/ind.). But macrofauna settlement presents a relative homogeneity between the beds (index Jaccard = 0.63). Its abundance was three times higher in the planted bed than in the control. From the surface to the bottom of the beds, macrofauna diversity and abundance decreased and were heavily dominated by Annelida. The significant relationships were only observed between Insecta and Myriapoda in the control.     

Development of Real-Time PCR Methods for the Detection of Bacterial Meningitis Pathogens without DNA Extraction

Neisseria meningitidis (Nm), Haemophilus influenzae (Hi), and Streptococcus pneumoniae (Sp) are the lead causes of bacterial meningitis. Detection of these pathogens from clinical specimens using traditional real-time PCR (rt-PCR) requires DNA extraction to remove the PCR inhibitors prior to testing, which is time consuming and labor intensive. In this study, five species-specific (Nm-sodC and -ctrA, Hi-hpd#1 and -hpd#3 and Sp-lytA) and six serogroup-specific rt-PCR tests (A, B, C, W, X, Y) targeting Nm capsular genes were evaluated in the two direct rt-PCR methods using PerfeCTa and 5x Omni that do not require DNA extraction. The sensitivity and specify of the two direct rt-PCR methods were compared to TaqMan traditional rt-PCR, the current standard rt-PCR method for the detection of meningitis pathogens. The LLD for all 11 rt-PCR tests ranged from 6,227 to 272,229 CFU/ml for TaqMan, 1,824–135,982 for 5x Omni, and 168–6,836 CFU/ml for PerfeCTa. The diagnostic sensitivity using TaqMan ranged from 89.2%-99.6%, except for NmB-csb, which was 69.7%. For 5x Omni, the sensitivity varied from 67.1% to 99.8%, with three tests below 90%. The sensitivity of these tests using PerfeCTa varied from 89.4% to 99.8%. The specificity ranges of the 11 tests were 98.0–99.9%, 97.5–99.9%, and 92.9–99.9% for TaqMan, 5x Omni, and PerfeCTa, respectively. PerfeCTa direct rt-PCR demonstrated similar or better sensitivity compared to 5x Omni direct rt-PCR or TaqMan traditional rt-PCR. Since the direct rt-PCR method does not require DNA extraction, it reduces the time and cost for processing CSF specimens, increases testing throughput, decreases the risk of cross-contamination, and conserves precious CSF. The direct rt-PCR method will be beneficial to laboratories with high testing volume.     

Repellent activity of Cymbopogon citratus and Tagetes minuta and their specific volatiles against Megalurothrips sjostedti

Cowpea is an important source of protein for people in Africa. However, the crop suffers major damage and yield losses due to bean flower thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae). Although companion plants are known to reduce the damage caused by insect pests, the role of their volatiles in repelling pests from target plants has been the subject of few investigations. Here, we used the Y‐tube olfactometer experiments and chemical analyses to investigate the effect of volatiles from cowpea flowers and two companion plants; lemongrass, Cymbopogon citratus and Mexican marigold, Tagetes minuta on the olfactory responses of M. sjostedti. The results revealed that M. sjostedti males and females were repelled by the volatiles from freshly cut leaves of C. citratus. The combination of freshly cut leaves of C. citratus and cowpea flower was repellent to females but not to males. The female thrips, but not males, were repelled by the volatiles from the vegetative stage of T. minuta. Fifty‐four compounds were identified in the volatiles from two herbal plants. Among the major compounds, citral and a 4‐component blend comprised of dihydrotagetone, (Z)‐3‐hexenyl acetate, limonene and (Z)‐β‐ocimene repelled females but dihydrotagetone alone attracted females. While myrcene combined with cowpea flower volatiles enhanced the attraction of females M. sjostedti, when tested alone was not attractive. These results highlight the potential of volatiles from C. citratus and T. minuta to repel M. sjostedti females. The use of these plants as companion plants in a cowpea cropping system could reduce M. sjostedti infestation.