A VirB4 ATPase of the mobile accessory genome orchestrates core genome-encoded features of physiology, metabolism, and virulence of Pseudomonas aeruginosa TBCF10839

Pseudomonas aeruginosa TBCF10839 is a highly virulent strain that can persist and replicate in human neutrophils. Screening of a signature-tagged mutagenesis (STM) TBCF10839 transposon library in phagocytosis tests identified a mutant that carried the transposon in the VirB4 homolog 5PG21 of an integrative and conjugative element (ICE)-associated type IV secretion system of the pKLC102 subtype. 5P21 TBCF10839 insertion mutants were deficient in metabolic versatility, secretion, quorum sensing, and virulence. The mutants were efficiently killed in phagocytosis tests in vitro and were avirulent in an acute murine airway infection model in vivo. The inactivation of 5PG21 silenced the rhl, las, and pqs operons and the gene expression for the synthesis of hydrogen cyanide, the antimetabolite l-2-amino-4-methoxy-trans-3-butenoic acid, and the H2- and H3-type VI secretion systems and their associated effectors. The mutants were impaired in the utilization of carbon sources and stored compounds that are not funneled into intermediary metabolism. This showcase demonstrates that a single gene of the mobile accessory genome can become an essential element to operate the core genome-encoded features of metabolism and virulence.

The influence of European legislation on the use of diagnostic test allergens for nasal allergen provocation in routine care of patients with allergic rhinitis

In patients with allergic rhinitis (AR), the nasal provocation test (NPT) is the standard procedure to evaluate the clinical response of the nasal mucosa to allergens with a high specificity and sensitivity. In AR, it is the only test that really measures the response of the diseased mucosa to allergens while skin prick test and serum IgE confirm the clinical suspicion of sensitization. Moreover, it is of special relevance in the detection of patients with Local Allergic Rhinitis (LAR), where general sensitization cannot be measured. For the evaluation of therapeutic interventions, NPT has been used for the clinical monitoring of antiallergic drugs and allergen specific immunotherapy. Legislation within the European Union (EU) defines allergens used for diagnostic tests like NPT to be medicinal products according to Directive 2001/83 EC, but national law is considering these products to be medicinal devices in a number of EU countries. Thus, NPT products are governed by different legislations and therefore standards throughout the EU. In consequence, allergens used for diagnostic purposes need different registrations and Marketing Authorization by national authorities. After a transition period, regulations of EU Directives are to be implemented in national law by all member states. At the moment, most EU countries have not fully implemented these Directives, however, it can be expected that most countries will implement it and enforce their rules within the next years. This development has a tremendous impact on the availability of diagnostic allergens for NPT in Europe and will make make nasal provocation testing very difficult if not impossible. We describe the current situation of diagnostic allergens under the special legislative conditions in the EU with special focus on allergen products used for NPT and the consequences for the diagnosis of AR and LAR.