Antimicrobial activity of prophage endolysins against critical Enterobacteriaceae antibiotic-resistant bacteria.

Enterobacteriaceae species are part of the 2017 World Health Organization antibiotic-resistant priority pathogens list for development of novel medicines. Multidrug-resistant Klebsiella pneumoniae is an increasing threat to public health and has become a relevant human pathogen involved in life-threatening infections. Phage therapy involves the use of phages or their lytic endolysins as bioagents for the treatment of bacterial infectious diseases. Gram-negative bacteria have an outer membrane, making difficult the access of endolysins to the peptidoglycan. Here, three endolysins from prophages infecting three distinct Enterobacterales species, Kp2948-Lys from K. pneumoniae, Ps3418-Lys from Providencia stuartii, and Kaer26608-Lys from Klebsiella aerogenes, were purified and exhibited antibacterial activity against their specific bacterium species verified by zymogram assays. These three endolysins were successfully associated to liposomes composed of dimyristoyl phosphatidyl choline (DMPC), dioleoyl phosphatidyl ethanolamine (DOPE) and cholesteryl hemisuccinate (CHEMS) at a molar ratio (4:4:2), with an encapsulation efficiency ranging from 24 to 27%. Endolysins encapsulated in liposomes resulted in higher antibacterial activity compared to the respective endolysin in the free form, suggesting that the liposome-mediated delivery system enhances fusion with outer membrane and delivery of endolysins to the target peptidoglycan. Obtained results suggest that Kp2948-Lys appears to be specific for K. pneumoniae, while Ps3418-Lys and Kaer26608-Lys appear to have a broader antibacterial spectrum. Endolysins incorporated in liposomes constitute a promising weapon, applicable in the several dimensions (human, animals and environment) of the One Health approach, against multidrug-resistant Enterobacteriaceae.

Liposomal Delivery of Newly Identified Prophage Lysins in a Pseudomonas aeruginosa Model.

Pseudomonas aeruginosa is a Gram-negative opportunistic bacterium that presents resistance to several antibiotics, thus, representing a major threat to human and animal health. Phage-derived products, namely lysins, or peptidoglycan-hydrolyzing enzymes, can be an effective weapon against antibiotic-resistant bacteria. Whereas in Gram-positive bacteria, lysis from without is facilitated by the exposed peptidoglycan layer, this is not possible in the outer membrane-protected peptidoglycan of Gram-negative bacteria. Here, we suggest the encapsulation of lysins in liposomes as a delivery system against Gram-negative bacteria, using the model of P. aeruginosa. Bioinformatic analysis allowed for the identification of 38 distinct complete prophages within 66 P. aeruginosa genomes (16 of which newly sequenced) and led to the identification of 19 lysins of diverse sequence and function, 5 of which proceeded to wet lab analysis. The four purifiable lysins showed hydrolytic activity against Gram-positive bacterial lawns and, on zymogram assays, constituted of autoclaved P. aeruginosa cells. Additionally, lysins Pa7 and Pa119 combined with an outer membrane permeabilizer showed activity against P. aeruginosa cells. These two lysins were successfully encapsulated in DPPC:DOPE:CHEMS (molar ratio 4:4:2) liposomes with an average encapsulation efficiency of 33.33% and 32.30%, respectively. The application of the encapsulated lysins to the model P. aeruginosa led to a reduction in cell viability and resulted in cell lysis as observed in MTT cell viability assays and electron microscopy. In sum, we report here that prophages may be important sources of new enzybiotics, with prophage lysins showing high diversity and activity. In addition, these enzybiotics following their incorporation in liposomes were able to potentiate their antibacterial effect against the Gram-negative bacteria P. aeruginosa, used as the model.

Biomarker Characterization and Prediction of Virulence and Antibiotic Resistance from Helicobacter pylori Next Generation Sequencing Data.

The Gram-negative bacterium Helicobacter pylori colonizes c.a. 50% of human stomachs worldwide and is the major risk factor for gastric adenocarcinoma. Its high genetic variability makes it difficult to identify biomarkers of early stages of infection that can reliably predict its outcome. Moreover, the increasing antibiotic resistance found in H. pylori defies therapy, constituting a major human health problem. Here, we review H. pylori virulence factors and genes involved in antibiotic resistance, as well as the technologies currently used for their detection. Furthermore, we show that next generation sequencing may lead to faster characterization of virulence factors and prediction of the antibiotic resistance profile, thus contributing to personalized treatment and management of H. pylori-associated infections. With this new approach, more and permanent data will be generated at a lower cost, opening the future to new applications for H. pylori biomarker identification and antibiotic resistance prediction.

Transfection of pulmonary cells by stable pDNA-polycationic hybrid nanostructured particles.

AIM: Cationically modified solid lipid nanoparticles (SLN) were investigated as plasmid DNA (pDNA) carriers and transfection agents for the pulmonary route. MATERIALS & METHODS: pDNA-loaded SLN were produced using glyceryl dibehenate or tristearate as matrix lipids and chitosan as surface charge modifier, and encapsulated by spray-drying in mannitol and trehalose microspheres. RESULTS: Nanoparticles of 200 nm, and zeta potential around +15 mV were produced. Electrophorectic analysis confirmed plasmid stability and integrity. The pDNA-loaded SLN were able to transfect the Calu-3 and A549 pulmonary cell lines, while showing low cytotoxicity. Microencapsulation of SLN yielded dry powders suitable for inhalation that protected pDNA from degradation. CONCLUSION: Microencapsulated SLN are a promising safe and effective carrier system for pulmonary gene delivery following pulmonary administration.

Maternal separation impairs long term-potentiation in CA1-CA3 synapses and hippocampal-dependent memory in old rats.

Exposure to chronic stress during the neonatal period is known to induce permanent long-term changes in the central nervous system and hipothalamic-pituitary-adrenal axis reactivity that are associated with increased levels of depression, anxiety, and cognitive impairments. In rodents, a validated model of early life stress is the maternal separation (MS) paradigm, which has been shown to have long-term consequences for the pups that span to adulthood. We hypothesized that the early life stress-associated effects could be exacerbated with aging, because it is often accompanied by cognitive decline. Using a MS model in which rat pups were separated from their mothers for 3 hours daily, during postnatal days 2-14, we evaluated the long-term functional consequences to aged animals (70-week-old), by measuring synaptic plasticity and cognitive performance. The baseline behavioral deficits of aged control rats were further exacerbated in MS animals, indicating that early-life stress induces sustained changes in anxiety-like behavior and hippocampal-dependent memory that are maintained much later in life. We then investigated whether these differences are linked to impaired function of hippocampal neurons by recording hippocampal long-term potentiation from Schaffer collaterals/CA1 synapses. The magnitude of the hippocampal long-term potentiation induced by high-frequency stimulation was significantly lower in aged MS animals than in age-matched controls. These results substantiate the hypothesis that the neuronal and endocrine alterations induced by early-life stress are long lasting, and are able to exacerbate the mild age-associated deficits.

The role of predictability in the stress response of a cichlid fish.

In recent years there has been an increasing interest in the cognitive abilities of fish with implications for animal welfare and management of rearing operations. Although it is known that psychological factors can modulate the stress response in mammals, this aspect has seldom been investigated within stress in fish. In this study we investigate whether the perception (appraisal) that fish make of significant environmental events modifies their behavioural and physiological response. For this purpose we have used a predictable vs. unpredictable paradigm for positive (feeding) and negative (confinement) events using the cichlid fish Oreochromis mossambicus as a model species. Results show that there is a differential effect of predictability for the feeding and confinement events. In the confinement experiment, predictability involved more attention to the visual cue and lower cortisol. The feeding event triggered higher levels of anticipatory behaviour and a tendency for higher cortisol in the predictable group. Therefore, predictable negative events reduce the cortisol response. Predictable positive events may elicit an anticipatory response, and when there is a significant delay between the visual cue and the actual occurrence of the event, it may also contain elements that can be interpreted as a stress response. These findings demonstrate that fish can appraise relevant aspects of the environment, with welfare implications for housing, husbandry and experimental procedures.