Accessing the In Vivo Efficiency of Clinically Isolated Phages against Uropathogenic and Invasive Biofilm-Forming Escherichia coli Strains for Phage Therapy.

Escherichia coli is one of the most common members of the intestinal microbiota. Many of its strains are associated with various inflammatory infections, including urinary or gut infections, especially when displaying antibiotic resistance or in patients with suppressed immune systems. According to recent reports, the biofilm-forming potential of E. coli is a crucial factor for its increased resistance against antibiotics. To overcome the limitations of using antibiotics against resistant E. coli strains, the world is turning once more towards bacteriophage therapy, which is becoming a promising candidate amongst the current personalized approaches to target different bacterial infections. Although matured and persistent biofilms pose a serious challenge to phage therapy, they can still become an effective alternative to antibiotic treatment. Here, we assess the efficiency of clinically isolated phages in phage therapy against representative clinical uropathogenic and invasive biofilm-forming E. coli strains. Our results demonstrate that irrespective of host specificity, bacteriophages producing clear plaques with a high burst size, and exhibiting depolymerizing activity, are good candidates against biofilm-producing E. coli pathogens as verified from our in vitro and in vivo experiments using Galleria mellonella where survival was significantly increased for phage-therapy-treated larvae.

Development of a ternary cyclodextrin-arginine-ciprofloxacin antimicrobial complex with enhanced stability.

Designing useful functionalities in clinically validated, old antibiotics holds promise to provide the most economical solution for the global lack of effective antibiotics, as undoubtedly a serious health threat. Here we show that using the surface chemistry of the cyclodextrin (ßCD) cycle and arginine (arg) as a linker, provides more stable ternary antibiotic complex (ßCD-arg-cpx). In contrast to classical less stable inclusion complexes, which only modify antibiotic solubility, here-presented ternary complex is more stable and controls drug release. The components of the complex intensify interactions with bacterial membranes and increase the drug's availability inside bacterial cells, thereby improving its antimicrobial efficacy and safety profile. Multifunctional antibiotics, formulated as drug delivery systems per se, that take the drug to the site of action, maximize its efficacy, and provide optical detectability are envisaged as the future in fighting against infections. Their role as a tool against multiresistant strains remains as interesting challenge open for further research.

Utility of Galleria mellonella larvae for evaluating nanoparticle toxicology.

The use of nanoparticles in consumer products is currently on the rise, so it is important to have reliable methods to predict any associated toxicity effects. Traditional in vitro assays fail to mimic true physiological responses of living organisms against nanoparticles whereas murine in vivo models are costly and ethically controversial. For these reasons, this study aimed to evaluate the efficacy of Galleria mellonella as an alternative, non-rodent in vivo model for examining nanoparticle toxicity. Silver, selenium, and functionalized gold nanoparticles were synthesized, and their toxicity was assessed in G. mellonella larvae. The degree of acute toxicity effects caused by each type of NP was efficiently detected by an array of indicators within the larvae: LD50 calculation, hemocyte proliferation, NP distribution, behavioral changes, and histological alterations. G. mellonella larvae are proposed as a nanotoxicological model that can be used as a bridge between in vitro and in vivo murine assays in order to obtain better predictions of NP toxicity.

A clearing protocol for Galleria mellonella larvae: Visualization of internalized fluorescent nanoparticles.

Light scattering is a challenge for imaging three-dimensional organisms. A number of new tissue clearing methodologies have been described in recent years, increasing the utilities of clearing techniques to obtain transparent samples. Here, we describe the optimization of a suitable and novel protocol for clearing Galleria mellonella larvae, an alternative infection animal model with a promising potential for the toxicological evaluation of different molecules and materials. This has allowed the visualization of internalised fluorescent nanoparticles using confocal microscopy, opening the door to a wide range of different applications.

Monitoring Gene Expression during a Galleria mellonella Bacterial Infection.

Galleria mellonella larvae are an alternative in vivo model that has been extensively used to study the virulence and pathogenicity of different bacteria due to its practicality and lack of ethical constraints. However, the larvae possess intrinsic autofluorescence that obstructs the use of fluorescent proteins to study bacterial infections, hence better methodologies are needed. Here, we report the construction of a promoter probe vector with bioluminescence expression as well as the optimization of a total bacterial RNA extraction protocol to enhance the monitoring of in vivo infections. By employing the vector to construct different gene promoter fusions, variable gene expression levels were efficiently measured in G. mellonella larvae at various time points during the course of infection and without much manipulation of the larvae. Additionally, our optimized RNA extraction protocol facilitates the study of transcriptional gene levels during an in vivo infection. The proposed methodologies will greatly benefit bacterial infection studies as they can contribute to a better understanding of the in vivo infection processes and pathogen-mammalian host interactions.

Mycolicibacterium brumae Is a Safe and Non-Toxic Immunomodulatory Agent for Cancer Treatment.

Intravesical Mycobacterium bovis Bacillus Calmette-Guérin (BCG) immunotherapy remains the gold-standard treatment for non-muscle-invasive bladder cancer patients, even though half of the patients develop adverse events to this therapy. On exploring BCG-alternative therapies, Mycolicibacterium brumae, a nontuberculous mycobacterium, has shown outstanding anti-tumor and immunomodulatory capabilities. As no infections due to M. brumae in humans, animals, or plants have been described, the safety and/or toxicity of this mycobacterium have not been previously addressed. In the present study, an analysis was made of M. brumae- and BCG-intravenously-infected severe combined immunodeficient (SCID) mice, M. brumae-intravesically-treated BALB/c mice, and intrahemacoelic-infected-Galleria mellonella larvae. Organs from infected mice and the hemolymph from larvae were processed to count bacterial burden. Blood samples from mice were also taken, and a wide range of hematological and biochemical parameters were analyzed. Finally, histopathological alterations in mouse tissues were evaluated. Our results demonstrate the safety and non-toxic profile of M. brumae. Differences were observed in the biochemical, hematological and histopathological analysis between M. brumae and BCG-infected mice, as well as survival curves rates and colony forming units (CFU) counts in both animal models. M. brumae constitutes a safe therapeutic biological agent, overcoming the safety and toxicity disadvantages presented by BCG in both mice and G. mellonella animal models.

Novel Oleanolic and Maslinic Acid Derivatives as a Promising Treatment against Bacterial Biofilm in Nosocomial Infections: An in Vitro and in Vivo Study.

Oleanolic acid (OA) and maslinic acid (MA) are pentacyclic triterpenic compounds that abound in industrial olive oil waste. These compounds have renowned antimicrobial properties and lack cytotoxicity in eukaryotic cells as well as resistance mechanisms in bacteria. Despite these advantages, their antimicrobial activity has only been tested in vitro, and derivatives improving this activity have not been reported. In this work, a set of 14 OA and MA C-28 amide derivatives have been synthesized. Two of these derivatives, MA-HDA and OA-HDA, increase the in vitro antimicrobial activity of the parent compounds while reducing their toxicity in most of the Gram-positive bacteria tested, including a methicillin-resistant Staphylococcus aureus-MRSA. MA-HDA also shows an enhanced in vivo efficacy in a Galleria mellonella invertebrate animal model of infection. A preliminary attempt to elucidate their mechanism of action revealed that these compounds are able to penetrate and damage the bacterial cell membrane. More significantly, their capacity to reduce antibiofilm formation in catheters has also been demonstrated in two sets of conditions: a static and a more challenged continuous-flow S. aureus biofilm.