Interaction of gentamicin sulfate with alginate and consequences on the physico-chemical properties of alginate-containing biofilms

A multifunctional sateen woven dressings for treatment of skin injuries

Cutaneous wounds with impaired healing such as diabetic ulcers and burns constitute major and rapidly growing threat to healthcare systems worldwide. Accelerating wound healing requires the delivery of biological factors that induce angiogenesis, support cellular proliferation, and modulate inflammation while minimizing infection. In this study, we engineered a dressing made by weaving of composite fibers (CFs) carrying mesenchymal stem cells (MSCs) and a model antibiotic using a scalable sateen textile technique. In this regard, two different sets of CFs carrying MSCs or an antimicrobial agent were used to generate a multifunctional dressing. According to cell viability and metabolic activity as CCK-8 and live/dead with qRT-PCR results, more than %90 the encapsulated MSCs remain viable for 28 days and their expression levels of the wound repair factors including ECM remodeling, angiogenesis and immunomodulatory maintained in MSCs post dressing manufacturing for 14 days. Post 10 days culture of the dressing, MSCs within CFs had 10-fold higher collagen synthesis (p < 0.0001) determined by hydroxyproline assay which indicates the enhanced healing properties. According to in vitro antimicrobial activity results determined by disk diffusion and broth microdilution tests, the first day and the total amount of release gentamicin loaded dressing samples during the 28 days were higher than determined minimal inhibition concentration (MIC) values for S. aureus and K. pneumonia without negatively impacting the viability and functionality of encapsulated MSCs within the dressing. The dressing is also flexible and can conform to skin curvatures making the dressing suitable for the treatment of different skin injuries such as burns and diabetic ulcers.

Interplay between biofilm microenvironment and pathogenicity of Pseudomonas aeruginosa in cystic fibrosis lung chronic infection

Pseudomonas aeruginosa (PA) is a highly, if not the most, versatile microorganism capable of colonizing diverse environments. One of the niches in which PA is able to thrive is the lung of cystic fibrosis (CF) patients. Due to a genetic aberration, the lungs of CF-affected patients exhibit impaired functions, rendering them highly susceptible to bacterial colonization. Once PA attaches to the epithelial surface and transitions to a mucoid phenotype, the infection becomes chronic, and antibiotic treatments become inefficient. Due to the high number of affected people and the severity of this infection, CF-chronic infection is a well-documented disease. Still, numerous aspects of PA CF infection remain unclear. The scientific reports published over the last decades have stressed how PA can adapt to CF microenvironmental conditions and how its surrounding matrix of extracellular polymeric substances (EPS) plays a key role in its pathogenicity. In this context, it is of paramount interest to present the nature of the EPS together with the local CF-biofilm microenvironment. We review how the PA biofilm microenvironment interacts with drugs to contribute to the pathogenicity of CF-lung infection. Understanding why so many drugs are inefficient in treating CF chronic infection while effectively treating planktonic PA is essential to devising better therapeutic targets and drug formulations.

Pseudomonas aeruginosa biofilm dispersion by the mouse antimicrobial peptide CRAMP

Pseudomonas aeruginosa (P. aeruginosa) is a known bacterium that produces biofilms and causes severe infection. Furthermore, P. aeruginosa biofilms are extremely difficult to eradicate, leading to the development of chronic and antibiotic-resistant infections. Our previous study showed that a cathelicidin-related antimicrobial peptide (CRAMP) inhibits the formation of P. aeruginosa biofilms and markedly reduces the biomass of preformed biofilms, while the mechanism of eradicating bacterial biofilms remains elusive. Therefore, in this study, the potential mechanism by which CRAMP eradicates P. aeruginosa biofilms was investigated through an integrative analysis of transcriptomic, proteomic, and metabolomic data. The omics data revealed CRAMP functioned against P. aeruginosa biofilms by different pathways, including the Pseudomonas quinolone signal (PQS) system, cyclic dimeric guanosine monophosphate (c-di-GMP) signalling pathway, and synthesis pathways of exopolysaccharides and rhamnolipid. Moreover, a total of 2914 differential transcripts, 785 differential proteins, and 280 differential metabolites were identified. A series of phenotypic validation tests demonstrated that CRAMP reduced the c-di-GMP level with a decrease in exopolysaccharides, especially alginate, in P. aeruginosa PAO1 biofilm cells, improved bacterial flagellar motility, and increased the rhamnolipid content, contributing to the dispersion of biofilms. Our study provides new insight into the development of CRAMP as a potentially effective antibiofilm dispersant.

Controlled and Local Delivery of Antibiotics by 3D Core/Shell Printed Hydrogel Scaffolds to Treat Soft Tissue Infections

Soft tissue infections in open fractures or burns are major cause for high morbidity in trauma patients. Sustained, long-term and localized delivery of antimicrobial agents is needed for early eradication of these infections. Traditional (topical or systemic) antibiotic delivery methods are associated with a variety of problems, including their long-term unavailability and possible low local concentration. Novel approaches for antibiotic delivery via wound coverage/healing scaffolds are constantly being developed. Many of these approaches are associated with burst release and thus seldom maintain long-term inhibitory concentrations. Using 3D core/shell extrusion printing, scaffolds consisting of antibiotic depot (in the core composed of low concentrated biomaterial ink 3% alginate) surrounded by a denser biomaterial ink (shell) were fabricated. Denser biomaterial ink (composed of alginate and methylcellulose or alginate, methylcellulose and Laponite) retained scaffold shape and modulated antibiotic release kinetics. Release of antibiotics was observed over seven days, indicating sustained release characteristics and maintenance of potency. Inclusion of Laponite in shell, significantly reduced burst release of antibiotics. Additionally, the effect of shell thickness on release kinetics was demonstrated. Amalgamation of such a modular delivery system with other biofabrication methods could potentially open new strategies to simultaneously treat soft tissue infections and aid wound regeneration.

A Hyaluronic Acid Hydrogel Loaded with Gentamicin and Vancomycin Successfully Eradicates Chronic Methicillin-Resistant Staphylococcus aureus Orthopedic Infection in a Sheep Model

Implantable orthopedic devices have had an enormously positive impact on human health; however, despite best practice, patients are prone to developing orthopedic device-related infections (ODRI) that have high treatment failure rates. One barrier to the development of improved treatment options is the lack of an animal model that may serve as a robust preclinical assessment of efficacy. We present a clinically relevant large animal model of chronic methicillin-resistant Staphylococcus aureus (MRSA) ODRI that persists despite current clinical practice in medical and surgical treatment at rates equivalent to clinical observations. Furthermore, we showed that an injectable, thermoresponsive, hyaluronic acid-based hydrogel loaded with gentamicin and vancomycin outperforms current clinical practice treatment in this model, eliminating bacteria from all animals. These results confirm that local antibiotic delivery with an injectable hydrogel can dramatically increase treatment success rates beyond current clinical practice, with efficacy proven in a robust animal model.

Rhamnolipids and surfactin inhibit the growth or formation of oral bacterial biofilm

Background

Bacteria survive in various environments by forming biofilms. Bacterial biofilms often cause significant problems to medical instruments and industrial processes. Techniques to inhibit biofilm formation are essential and have wide applications. In this study, we evaluated the ability of two types of biosurfactants (rhamnolipids and surfactin) to inhibit growth and biofilm formation ability of oral pathogenic bacteria such as Aggregatibacter actinomycetemcomitans, Streptococcus mutans, and Streptococcus sanguinis.

Results

Rhamnolipids inhibited the growth and biofilm formation ability of all examined oral bacteria. Surfactin showed effective inhibition against S. sanguinis ATCC10556, but lower effects toward A. actinomycetemcomitans Y4 and S. mutans UA159. To corroborate these results, biofilms were observed by scanning electron microscopy (SEM) and confocal microscopy. The observations were largely in concordance with the biofilm assay results. We also attempted to determine the step in the biofilm formation process that was inhibited by biosurfactants. The results clearly demonstrated that rhamnolipids inhibit biofilm formation after the initiation process, however, they do not affect attachment or maturation.

Conclusions

Rhamnolipids inhibit oral bacterial growth and biofilm formation by A. actinomycetemcomitans Y4, and may serve as novel oral drug against localized invasive periodontitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-020-02034-9.

Francisella novicida and F. philomiragia biofilm features conditionning fitness in spring water and in presence of antibiotics

Biofilms are currently considered as a predominant lifestyle of many bacteria in nature. While they promote survival of microbes, biofilms also potentially increase the threats to animal and public health in case of pathogenic species. They not only facilitate bacteria transmission and persistence, but also promote spreading of antibiotic resistance leading to chronic infections. In the case of Francisella tularensis, the causative agent of tularemia, biofilms have remained largely enigmatic. Here, applying live and static confocal microscopy, we report growth and ultrastructural organization of the biofilms formed in vitro by these microorganisms over the early transition from coccobacillary into coccoid shape during biofilm assembly. Using selective dispersing agents, we provided evidence for extracellular DNA (eDNA) being a major and conserved structural component of mature biofilms formed by both F. subsp. novicida and a human clinical isolate of F. philomiragia. We also observed a higher physical robustness of F. novicida biofilm as compared to F. philomiragia one, a feature likely promoted by specific polysaccharides. Further, F. novicida biofilms resisted significantly better to ciprofloxacin than their planktonic counterparts. Importantly, when grown in biofilms, both Francisella species survived longer in cold water as compared to free-living bacteria, a trait possibly associated with a gain in fitness in the natural aquatic environment. Overall, this study provides information on survival of Francisella when embedded with biofilms that should improve both the future management of biofilm-related infections and the design of effective strategies to tackle down the problematic issue of bacteria persistence in aquatic ecosystems.