Genomics of the new species Kingella negevensis: diagnostic issues and identification of a locus encoding a RTX toxin

Kingella kingae, producing the cytotoxic RTX protein, is a causative agent of serious infections in humans such as bacteremia, endocarditis and osteoarticular infection, especially in young children. Recently, Kingella negevensis, a related species, has been isolated from the oral cavity of healthy children. In this study, we report the isolation of K. negevensis strain eburonensis, initially misidentified as K. kingae with MALDI-TOF MS, from a vaginal specimen of a patient suffering of vaginosis. The genome sequencing and analysis of this strain together with comparative genomics of the Kingella genus revealed that K. negevensis possesses a full homolog of the rtx operon of K. kingae involved in the synthesis of the RTX toxin. We report that a K. kingae specific diagnostic PCR, based on the rtxA gene, was positive when tested on K. negevensis strain eburonensis DNA. This cross-amplification, and risk of misidentification, was confirmed by in silico analysis of the target gene sequence. To overcome this major diagnostic issue we developed a duplex real-time PCR to detect and distinguish K. kingae and K. negevensis. In addition to this, the identification of K. negevensis raises a clinical issue in term of pathogenic potential given the production of a RTX hemolysin.     

Factors affecting the efficacy of the leaf-spot fungus Mycosphaerella polygoni-cuspidati (Ascomycota): A potential classical biological control agent of the invasive alien weed Fallopia japonica (Polygonaceae) in the UK

Fallopia japonica, commonly known as Japanese knotweed, is an increasingly serious invasive alien weed in the UK and large parts of mainland Europe, as well as in North America. There is an urgent need to include classical biological control (CBC) into any integrated pest management strategy. The leaf-spot pathogen Mycosphaerella polygoni-cuspidati, a coevolved natural enemy of F. japonica present throughout its native Japanese range, is considered to have high potential as a CBC agent. In this study, the disease development of M. polygoni-cuspidati in the field and the optimum infection parameters under controlled conditions were investigated to elucidate the pathogen’s potential biocontrol efficacy against Japanese knotweed. Field observation in Japan showed that M. polygoni-cuspidati caused severe damage to its host plant. When sentinel knotweed plants from the UK were placed amongst naturally-infected field populations of F. japonica, disease incidence and severity were highest in July when monthly precipitation was also highest. In greenhouse inoculation tests, F. japonica was shown to be most susceptible at the young leaf stage (7–12 days after opening). Disease severity was highest after an initial dew period of 42–48 h, and severe defoliation followed inoculation at a temperature range of 15–25 °C. The optimum post-inoculation temperature after dew treatment for disease severity was 20–25 °C. In field inoculation tests, high disease incidence and severity indicate that the pathogen has the potential to control the plant effectively in the field. Humidity and temperature were shown to be the main factors influencing disease expression and lesion development of M. polygoni-cuspidati in a field situation. These results provide valuable information for any future use of M. polygoni-cuspidati as a CBC agent for management of Japanese knotweed in the UK.     

Bile acids target mitofusin 2 to differentially regulate innate immunity in physiological versus cholestatic conditions

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Infective complications after transcatheter aortic valve implantation: results from a single centre

After its first introduction in 2002, transcatheter aortic valve implantation (TAVI) has continuously gained more foothold for the treatment of severe aortic stenosis and is nowadays a viable treatment option for inoperable patients or patients at high risk for conventional surgical aortic valve replacement. Although ideally carried out in a so-called hybrid room, incorporating both the strict hygiene and advanced life support possibilities of the operating theatre and the imaging and percutaneous arsenal of the catheterisation suite, in most centres TAVI is at present performed in the catheterisation laboratory. This may raise concern about an increased risk of infection, since there the criteria that are applied regarding disinfection and sterilisation are not as stringent as those of the operating theatre. Therefore, we retrospectively assessed the number of infective complications in patients undergoing TAVI in the catheterisation lab of our institution. Eleven out of 73 patients developed a postprocedural infection, one of which could be attributed to the procedure itself, being superinfection of a surgical groin cut-down. Our conclusion is that percutaneous aortic valve implantation in a catheterisation laboratory is not associated with an increased risk of infective complications.     

Systems biology of pathogen-host interaction: Networks of protein-protein interaction within pathogens and pathogen-human interactions in the post-genomic era

Infectious diseases comprise some of the leading causes of death and disability worldwide. Interactions between pathogen and host proteins underlie the process of infection. Improved understanding of pathogen-host molecular interactions will increase our knowledge of the mechanisms involved in infection, and allow novel therapeutic solutions to be devised. Complete genome sequences for a number of pathogenic microorganisms, as well as the human host, has led to the revelation of their protein-protein interaction (PPI) networks. In this post-genomic era, pathogen-host interactions (PHIs) operating during infection can also be mapped. Detailed systematic analyses of PPI and PHI data together are required for a complete understanding of pathogenesis of infections. Here we review the striking results recently obtained during the construction and investigation of these networks. Emphasis is placed on studies producing large-scale interaction data by high-throughput experimental techniques.     

Dental screening of medical patients for oral infections and inflammation: consideration of risk and benefit

The primary purpose of preoperative dental screening of medical patients is to detect acute or chronic oral conditions that may require management prior to planned medical interventions. The aim of this communication is to discuss the background of preoperative dental screening and the link between dental pathologies and systemic diseases.     

In vivo Imaging Method to Distinguish Acute and Chronic Inflammation

Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that distinguish acute and chronic inflammation in mouse models. With tissue damage or pathogen invasion, neutrophils are the first line of defense, playing a major role in mediating the acute inflammatory response. As the inflammatory reaction progresses, circulating monocytes gradually migrate into the site of injury and differentiate into mature macrophages, which mediate chronic inflammation and promote tissue repair by removing tissue debris and producing anti-inflammatory cytokines. Intraperitoneal injection of luminol (5-amino-2,3-dihydro-1,4-phthalazinedione, sodium salt) enables detection of acute inflammation largely mediated by tissue-infiltrating neutrophils. Luminol specifically reacts with the superoxide generated within the phagosomes of neutrophils since bioluminescence results from a myeloperoxidase (MPO) mediated reaction. Lucigenin (bis-N-methylacridinium nitrate) also reacts with superoxide in order to generate bioluminescence. However, lucigenin bioluminescence is independent of MPO and it solely relies on phagocyte NADPH oxidase (Phox) in macrophages during chronic inflammation. Together, luminol and lucigenin allow non-invasive visualization and longitudinal assessment of different phagocyte populations across both acute and chronic inflammatory phases. Given the important role of inflammation in a variety of human diseases, we believe this non-invasive imaging method can help investigate the differential roles of neutrophils and macrophages in a variety of pathological conditions.     

Preferential infectivity of entomopathogenic nematodes in an envenomed host

Entomopathogenic nematodes and parasitoid wasps are used as biological control agents for management of insect pests such as the Indian meal moth, Plodia interpunctella. The parasitoid wasp Habrobracon hebetor injects a paralytic venom into P. interpunctella larvae before laying eggs. A previous study reported that the entomopathogenic nematode Heterorhabditis indica preferentially infects P. interpunctella that have been envenomed by H. hebetor while results in this study showed a similar preference by the entomopathogenic nematode, Steinernema glaseri. We therefore tested four hypotheses for why nematode infection rates are higher in envenomed hosts: (1) elevated CO₂ emission from envenomed hosts attracts nematodes, (2) paralysis prevents hosts from escaping nematodes, (3) volatile chemicals emitted from envenomed hosts attract nematodes and increase infection, and (4) reduced immune defenses in envenomed hosts increase nematode survival. Results showed that envenomed P. interpunctella larvae emitted lower amounts of CO₂ than non-envenomed larvae. Physical immobilization of P. interpunctella larvae did not increase infection rates by S. glaseri but did increase infection rates by H. indica. Emissions from envenomed hosts were collected and analyzed by thermal desorption gas chromatography/mass spectrometry. The most abundant compound, 3-methyl-3-buten-1-ol, was found to be an effective cue for S. glaseri attraction and infection but was not an effective stimulus for H. indica. Envenomed P. interpunctella exhibited a stronger immune response toward nematodes than non-envenomed hosts. Altogether, we conclude that different mechanisms underlie preferential infection in the two nematode species: host immobilization for H. indica and chemical cues for S. glaseri.