Pseudomonas aeruginosa lung infections are a major cause of death in cystic fibrosis and hospitalized patients. Treating these infections is becoming difficult due to the emergence of conventional antimicrobial multiresistance. While monosaccharides have proved beneficial against such bacterial lung infection, the design of several multivalent glycosylated macromolecules has been shown to be also beneficial on biofilm dispersion. In this study, calix[4]arene-based glycoclusters functionalized with galactosides or fucosides have been synthesized. The characterization of their inhibitory properties on Pseudomonas aeruginosa aggregation, biofilm formation, adhesion on epithelial cells, and destruction of alveolar tissues were performed. The antiadhesive properties of the designed glycoclusters were demonstrated through several in vitro bioassays. An in vivo mouse model of lung infection provided an almost complete protection against Pseudomonas aeruginosa with the designed glycoclusters.

Food-borne human infection with Campylobacter jejuni is a medical concern in both industrialized and developing countries. Efficient eradication of C. jejuni reservoirs within live animals and processed foods is limited by the development of antimicrobial resistances and by practical problems related to the use of conventional antibiotics in food processes. We have investigated the bacteriostatic and bactericidal activities of two phytochemicals, allyl-isothiocyanate (AITC), and benzyl isothiocyanate (BITC), against 24 C. jejuni isolates from chicken feces, human infections, and contaminated foods, as well as two reference strains NCTC11168 and 81-176. AITC and BITC displayed a potent antibacterial activity against C. jejuni. BITC showed a higher overall antibacterial effect (MIC of 1.25–5 μg mL−1) compared to AITC (MIC of 50–200 μg mL−1). Both compounds are bactericidal rather than bacteriostatic. The sensitivity levels of C. jejuni isolates against isothiocyanates were neither correlated with the presence of a GGT (γ-Glutamyl Transpeptidase) encoding gene in the genome, with antibiotic resistance nor with the origin of the biological sample. However the ggt mutant of C. jejuni 81-176 displayed a decreased survival rate compared to wild-type when exposed to ITC. This work determined the MIC of two ITC against a panel of C. jejuni isolates, showed that both compounds are bactericidal rather than bacteriostatic, and highlighted the role of GGT enzyme in the survival rate of C. jejuni exposed to ITC.

BackgroundPseudomonas aeruginosa (Pa) is a Gram-negative bacteria frequently involved in healthcare-associated pneumonia with poor clinical outcome. To face the announced post-antibiotic era due to increasing resistance and lack of new antibiotics, new treatment strategies have to be developed. Immunomodulation of the host response involved in outcome could be an alternative therapeutic target in Pa-induced lung infection. Kynurenines are metabolites resulting from tryptophan catabolism and are known for their immunomodulatory properties. Pa catabolizes tryptophan through the kynurenine pathway. Interestingly, many host cells also possess the kynurenine pathway, whose metabolites are known to control immune system homeostasis. Thus, bacterial metabolites may interfere with the host’s immune response. However, the kynurenine pathway in Pa, including functional enzymes, types and amounts of secreted metabolites remains poorly known. Using liquid chromatography coupled to mass spectrometry and different strains of Pa, we determined types and levels of metabolites produced by Pa ex vivo in growth medium, and the relevance of this production in vivo in a murine model of acute lung injury.ResultsEx vivo, Pa secretes clinically relevant kynurenine levels (μM to mM). Pa also secretes kynurenic acid and 3-OH-kynurenine, suggesting that the bacteria possess both a functional kynurenine aminotransferase and kynurenine monooxygenase. The bacterial kynurenine pathway is the major pathway leading to anthranilate production both ex vivo and in vivo. In the absence of the anthranilate pathway, the kynurenine pathway leads to kynurenic acid production.ConclusionPa produces and secretes several metabolites of the kynurenine pathway. Here, we demonstrate the existence of new metabolic pathways leading to synthesis of bioactive molecules, kynurenic acid and 3-OH-kynurenine in Pa. The kynurenine pathway in Pa is critical to produce anthranilate, a crucial precursor of some Pa virulence factors. Metabolites (anthranilate, kynurenine, kynurenic acid) are produced at sustained levels both ex vivo and in vivo leading to a possible immunomodulatory interplay between bacteria and host. These data may imply that pulmonary infection with bacteria highly expressing the kynurenine pathway enzymes could influence the equilibrium of the host’s tryptophan metabolic pathway, known to be involved in the immune response to infection. Further studies are needed to explore the effects of these metabolic changes on the pathophysiology of Pa infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0756-x) contains supplementary material, which is available to authorized users.

While NLRC4-dependent sensing of intracellular Gram-negative pathogens such as Salmonella enterica serovar typhimurium is a beneficial host response, NLRC4-dependent sensing of the Pseudomonas aeruginosa type 3 secretion system (T3SS) has been shown to be involved in pathogenicity. In mice, different pathogen-associated microbial patterns are sensed by the combination of the NLRC4-inflammasome with different neuronal apoptosis inhibitory proteins (NAIPs). NAIP2 is involved in sensing PscI, an inner-rod protein of the P. aeruginosa T3SS. Surprisingly, only a single human NAIP (hNAIP) has been found. Moreover, there is no description of hNAIP-NLRC4 inflammasome recognition of T3SS inner-rod proteins in humans. Here, we show that the P. aeruginosa T3SS inner-rod protein PscI and needle protein PscF are both sensed by the hNAIP-NLRC4 inflammasome in human macrophages and PBMCs from healthy donors, allowing caspase-1 and IL-1β maturation and resulting in a robust inflammatory response. TLR4 and TLR2 are involved in redundantly sensing these two T3SS components.