An independent validation study of loci associated with nematode resistance in sheep

Gastrointestinal nematode infection is a constraint on sheep production worldwide. Selective breeding programmes to enhance resistance to nematode infection are currently being implemented in a number of countries. Identification of loci associated with resistance to infection or causative mutations for resistance would enable more effective selection. Loci associated with indicator traits for nematode resistance has been identified in previous studies. In this study, Scottish Blackface, Texel and Suffolk lambs were used to validate the effects at eight genomic regions previously associated with nematode resistance (OAR3, 4, 5, 7, 12, 13, 14, 21). No SNP was significantly associated with nematode resistance at the region‐wide level but seven SNPs in three of the regions (OAR4, 12, 14) were nominally associated with trichostrongyle egg count in this study and six of these were also significant when fitted as single SNP effects. Nematodirus egg count was nominally associated with SNPs on OAR3, 4, 7 and 12.     

Leucocyte recruitment and molecular fortification of keratinocytes triggered by streptococcal M1 protein

Streptococcus pyogenes of the M1 serotype is commonly associated with invasive streptococcal infections and development of streptococcal toxic shock syndrome. The M1 protein is a powerful inducer of inflammatory responses for several human cell types, but the reason why M1 protein‐related strains is over‐represented in invasive streptococcal diseases is still not understood. This study was undertaken to investigate if soluble M1 protein can aggravate the severity of streptococcal skin infections in respect to inflammation, leucocyte recruitment, and tissue remodelling as seen in patients with cellulitis and necrotizing fasciitis. We found that HaCaT cells are able to recruit activated leucocytes when encountering M1 protein. Neither the bacterial protein nor activated leucocytes caused cell damage on HaCaT cells, instead HaCaT cells responded to the bacterial virulence factor by releasing several proteins protective against bacterial infection and leucocyte responses. However, although not cytotoxic, M1 protein completely abolished wound healing abilities of HaCaT cells. Taken together, our results demonstrate that M1 protein is a critical virulence factor that can augment streptococcal skin infection suggesting that the protein is an interesting target for drug development.     

Competing for blood: the ecology of parasite resource competition in human malaria–helminth co‐infections

Ecological theory suggests that co‐infecting parasite species can interact within hosts directly, via host immunity and/or via resource competition. In mice, competition for red blood cells (RBCs) between malaria and bloodsucking helminths can regulate malaria population dynamics, but the importance of RBC competition in human hosts was unknown. We analysed infection density (i.e. the concentration of parasites in infected hosts), from a 2‐year deworming study of over 4000 human subjects. After accounting for resource‐use differences among parasites, we find evidence of resource competition, priority effects and a competitive hierarchy within co‐infected individuals. For example reducing competition via deworming increased Plasmodium vivax densities 2.8‐fold, and this effect is limited to bloodsucking hookworms. Our ecological, resource‐based perspective sheds new light into decades of conflicting outcomes of malaria–helminth co‐infection studies with significant health and transmission consequences. Beyond blood, investigating within‐human resource competition may bring new insights for improving human health.     

Horizontal Gene Transfer of “Prototype” Nramp in Bacteria

Eukaryotic Nramp genes encode divalent metal ion permeases important for nutrition and resistance to microbial infection. Bacterial homologs encode proton-dependent transporters of manganese (MntH), and other divalent metal ions. Bacterial MntH were classified in three homology groups (A, B, C) and MntH C further subdivided in C, C, C. The proteins from C. tepidum (MntH B) and E. faecalis (MntH C1, 2), divergent in sequence and hydropathy profile, conferred increased metal sensitivity when expressed in E. coli, suggesting conservation of divalent metal transport function in MntH B and C. Several genomic evidence suggest horizontal gene transfer (HGT) of mntH C genes: (i) The enterobacteria Wigglesworthia mntH C gene is linked to an Asn t-RNA, and its sequence most conserved with Gram positive bacteria homologs; (ii) all the C genes identified in oral streptococcaceae are associated with different potentially mobile DNA elements; (iii) Lactococcus lactis and Burkholderia mallei genomes contain an mntH gene prematurely terminated and a novel full-length mntH C gene; (iv) remarkable sequence relatedness between the unicellular alga C. reinhardtii prototype Nramp and some MntH C (e.g., Nostoc spp., Listeria spp.) suggests HGT between Eukarya and Bacteria. Other prototype Nramp genes (intronless, encoding proteins strongly conserved with MntH A and B proteins) identified in invertebrates represent a possible source for transfer of Nramp genes toward opportunistic bacteria. This study demonstrates complex evolution of MntH in Bacteria. It is proposed that prototype Nramp are ancestors of bacterial MntH C proteins, which could facilitate bacterial infection. Equally contributing authors (Etienne Richer and Pascal Courville).     

Detection of Ralstonia solanacearum in Soil and Weeds from Commercial Tomato Fields Using Immunocapture and the Polymerase Chain Reaction

A detection assay for Ralstonia solanacearum in soil and weeds was developed by combining immunocapture and the polymerase chain reaction (IC‐PCR). Anti‐R. solanacearum polyclonal antibodies were produced in a white female rabbit and Dynal^® super‐paramagnetic beads were coated with purified immunoglobulinG (IgG). Using IC‐PCR, the 718 bp target DNA was amplified at a detection threshold of approximately 10⁴ colony‐forming units (CFU) bacteria per millilitre of suspension. DNA was not amplified in soil suspensions derived from autoclaved and non‐autoclaved soils, which contained R. solanacearum at 1–10⁵ CFU/g soil. However, a positive PCR result was obtained when bacteria in the soil suspensions were first enriched in nutrient broth. IC‐PCR detected R. solanacearum in tomato stems 24 h after inoculation by stem puncture with a suspension containing approximately 10⁵ CFU/ml. IC‐PCR detected the bacterium in 28 of 55 (51%) weeds and 10 of 32 (31%) soil samples. Of the weeds, Physalis minima, Amaranthus spinosus and Euphorbia hirta had the highest incidence of infection. R. solanacearum was not detected in soil taken from fallow fields, but it was discovered in some weed species. Symptomless tomato and pepper plants collected from the fields in which tomato bacterial wilt had previously occurred were found to contain R. solanacearum. These discoveries suggest that weeds and latent hosts may play a role in the survival of R. solanacearum between cropping cycles.     

Drugs to cure avian influenza infection – multiple ways to prevent cell death

New treatments and new drugs for avian influenza virus (AIV) infection are developed continually, but there are still high mortality rates. The main reason may be that not all cell death pathways induced by AIV were blocked by the current therapies. In this review, drugs for AIV and associated acute respiratory distress syndrome (ARDS) are summarized. The roles of antioxidant (vitamin C) and multiple immunomodulators (such as Celecoxib, Mesalazine and Eritoran) are discussed. The clinical care of ARDS may result in ischemia reperfusion injury to poorly ventilated alveolar cells. Cyclosporin A should effectively inhibit this kind of damages and, therefore, may be the key drug for the survival of patients with virus-induced ARDS. Treatment with protease inhibitor Ulinastatin could also protect lysosome integrity after the infection. Through these analyses, a large drug combination is proposed, which may hypothetically greatly reduce the mortality rate.     

Pan-ebolavirus protective therapy by two multifunctional human antibodies

1. Download : Download high-res image (192KB)
2. Download : Download full-size image

     

铜绿假单胞菌的院内感染分布及耐药性的调查

目的了解铜绿假单胞菌（PA）在医院内感染的分布特点及其耐药性,指导临床合理用药,降低医院感染率。方法回顾分析2005年1月至2008年11月我院临床分离的铜绿假单胞菌152株,按WHO推荐的NC-CLS标准方法（K—B法）进行药敏试验,分析菌株的临床分布特征及体外药敏结果。结果铜绿假单胞菌在临床上主要以呼吸道感染为主。在17种临床常用抗生素中,多表现为多重耐药。美洛培南、亚胺培南及左旋氧氟沙星抗PA效果最好,耐药率分别只有14．47％、14．47和5．26％。结论多重耐药铜绿假单胞菌在临床广泛存在,应当根据临床体外药敏结果合理选择抗菌药物进行治疗,以取得良好临床效果并减少耐药菌产生;同时规范院内感染控制措施,减少耐药菌株的播散。