Effect of fusafungine on adherence of Haemophilus influenzae type b to human epithelial cells in vitro

Bacillus subtilis as heterologous host for the secretory production of the non-ribosomal cyclodepsipeptide enniatin

The heterologous expression of genes or gene clusters in microbial hosts, followed by metabolic engineering of biosynthetic pathways, is key to access industrially and pharmaceutically relevant compounds in an economically affordable and sustainable manner. Therefore, platforms need to be developed, which provide tools for the controlled synthesis of bioactive compounds. The Gram-positive bacterium Bacillus subtilis is a promising candidate for such applications, as it is generally regarded as a safe production host, its physiology is well investigated and a variety of tools is available for its genetic manipulation. Furthermore, this industrially relevant bacterium provides a high secretory potential not only for enzymes but also for primary and secondary metabolites. In this study, we present the first heterologous expression of an eukaryotic non-ribosomal peptide synthetase gene (esyn) coding for the biosynthesis of the small molecule enniatin in B. subtilis. Enniatin is a pharmaceutically used cyclodepsipeptide for treatment of topical bacterial and fungal infections. We generated various enniatin-producing B. subtilis strains, allowing for either single chromosomal or plasmid-based multi-copy expression of the esyn cluster under the control of an acetoin-inducible promoter system. Optimization of cultivation conditions, combined with modifications of the genetic background and multi-copy plasmid-based esyn expression, resulted in a secretory production of enniatin B. This work presents B. subtilis as a suitable host for the expression of heterologous eukaryotic non-ribosomal peptide synthetases (NRPS) clusters.

How to improve current therapeutic standards in upper respiratory infections: value of fusafungine

Despite guidelines and educational programs, systemic antibiotics and anti-inflammatory drugs are often inappropriately prescribed in upper respiratory tract infections (URTIs), although they are most often of viral origin, generally benign, and self-limiting with spontaneous recovery in more than 80% of cases. Reduced use of systemic antibiotics is crucial in the current context of concern about emerging antibiotic resistance and reducing unnecessary costs associated both with drug over-consumption and with the management of the consequences of antibiotic resistance. Local bacterial or viral infection of the airways induces an early inflammatory reaction. Although this inflammatory reaction has a beneficial effect in the capture and destruction of the pathogens, it can be responsible for deleterious tissue damage and vascular alterations leading to a self-perpetuating cycle of events. A wide array of medicines is available for symptomatic relief of URTIs: many of them are partially effective in reducing symptoms, but none is curative. Local administration of antibiotics and anti-inflammatory drugs allows drug delivery directly to the target site of infection and inflammation, i.e., the respiratory mucosa, thus enabling a higher concentration of the drug, which results in smaller doses to be given, decreased potential for systemic toxicity, fewer side effects, protection of other flora, and rapid relief. Fusafungine is a naturally occurring peptide antibiotic with anti-inflammatory properties, which selectively targets the tissue reaction and preserves the natural antibacterial and antiviral defences. It is indicated for topical use in nose and throat infections. A recent analysis of French general practitioners' (GPs) prescribing pattern in the field of URTIs has demonstrated that prescription of fusafungine has achieved what many educational programs have failed to do: a significant reduction in the 'real life' prescription of systemic antibiotics and antiinflammatory drugs, without the side effects of corticosteroids and vasoconstrictive agents, and without impact on microbial ecology.

Expression and modulation of ICAM-1, TNF-alpha and RANTES in human alveolar macrophages from lung-transplant recipients in vitro

Alveolar macrophages (AMs) play a central role in pulmonary inflammation in response to local stimuli. As a model for investigating anti-inflammatory drugs, we studied the effects of the cyclohexadepsipeptide antibiotic, fusafungine, and that of the glucocorticoid dexamethasone on the expression of ICAM-1, TNF-alpha and RANTES, induced in vitro by rIFN-gamma in human AMs freshly isolated from bronchoalveolar lavage fluid (BAL) obtained in lung-transplanted patients. ICAM-1 antigen expression, induced on AMs after 24 h of culture, was significantly inhibited by fusafungine in a concentration-dependent manner, as measured by flow cytometry analysis using an anti-CD54 monoclonal antibody. TNF-alpha production, but not RANTES release (measured by ELISA), was significantly inhibited. mRNA studies, by means of polymerase chain reaction amplification of complementary deoxyribonucleic acids (RT-PCR), showed no significant modification of mRNA levels, suggesting that fusafungine acts mainly at a post-transcriptional level. In the same conditions, dexamethasone significantly inhibited the release both of TNF-alpha and RANTES by AMs, mainly acting at the mRNA level, but had no effect on ICAM-1 expression. Assessment of the cellular and molecular targets of anti-inflammatory drugs in this model of human AM activation should lead to more appropriate treatment of inflammatory process of the respiratory tract. By virtue of its anti-inflammatory effects on alveolar macrophages, combined with its antibacterial properties, fusafungine should prove particularly suitable for local treatment of bacterial infections of the respiratory tract.