Antibiofilm activity of Prevotella species from the cystic fibrosis lung microbiota against Pseudomonas aeruginosa.

It is increasingly recognized that interspecies interactions may modulate the pathogenicity of Pseudomonas aeruginosa during chronic lung infections. Nevertheless, while the interaction between P. aeruginosa and pathogenic microorganisms co-infecting the lungs has been widely investigated, little is known about the influence of other members of the lung microbiota on the infection process. In this study, we focused on investigating the impact of Prevotella species isolated from the sputum of people with cystic fibrosis (pwCF) on biofilm formation and virulence factor production by P. aeruginosa. Screening of a representative collection of Prevotella species recovered from clinical samples showed that several members of this genus (8 out 10 isolates) were able to significantly reduce biofilm formation of P. aeruginosa PAO1, without impact on growth. Among the tested isolates, the strongest biofilm-inhibitory activity was observed for Prevotella intermedia and Prevotella nigrescens, which caused a reduction of up to 90% in the total biofilm biomass of several P. aeruginosa isolates from pwCF. In addition, a strain-specific effect of P. nigrescens on the ability of P. aeruginosa to produce proteases and pyocyanin was observed, with significant alterations in the levels of these virulence factors detected in LasR mutant strains. Overall, these results suggest that non-pathogenic bacteria from the lung microbiota may regulate pathogenicity traits of P. aeruginosa, and possibly affect the outcome of chronic lung infections.

Carbon source competition within the wound microenvironment can significantly influence infection progression.

It is becoming increasingly apparent that commensal skin bacteria have an important role in wound healing and infection progression. However, the precise mechanisms underpinning many of these probiotic interactions remain to be fully uncovered. In this work, we demonstrate that the common skin commensal Cutibacterium acnes can limit the pathogenicity of the prevalent wound pathogen Pseudomonas aeruginosa in vivo. We show that this impact on pathogenicity is independent of any effect on growth, but occurs through a significant downregulation of the Type Three Secretion System (T3SS), the primary toxin secretion system utilised by P. aeruginosa in eukaryotic infection. We also show a downregulation in glucose acquisition systems, a known regulator of the T3SS, suggesting that glucose availability in a wound can influence infection progression. C. acnes is well known as a glucose fermenting organism, and we demonstrate that topically supplementing a wound with glucose reverses the probiotic effects of C. acnes. This suggests that introducing carbon source competition within the wound microenvironment may be an effective way to prevent or limit wound infection.

Genome-scale model of Rothia mucilaginosa predicts gene essentialities and reveals metabolic capabilities.

Cystic fibrosis (CF), an inherited genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator gene, results in sticky and thick mucosal fluids. This environment facilitates the colonization of various microorganisms, some of which can cause acute and chronic lung infections, while others may positively impact the disease. Rothia mucilaginosa, an oral commensal, is relatively abundant in the lungs of CF patients. Recent studies have unveiled its anti-inflammatory properties using in vitro three-dimensional lung epithelial cell cultures and in vivo mouse models relevant to chronic lung diseases. Apart from this, R. mucilaginosa has been associated with severe infections. However, its metabolic capabilities and genotype-phenotype relationships remain largely unknown. To gain insights into its cellular metabolism and genetic content, we developed the first manually curated genome-scale metabolic model, iRM23NL. Through growth kinetics and high-throughput phenotypic microarray testings, we defined its complete catabolic phenome. Subsequently, we assessed the model's effectiveness in accurately predicting growth behaviors and utilizing multiple substrates. We used constraint-based modeling techniques to formulate novel hypotheses that could expedite the development of antimicrobial strategies. More specifically, we detected putative essential genes and assessed their effect on metabolism under varying nutritional conditions. These predictions could offer novel potential antimicrobial targets without laborious large-scale screening of knockouts and mutant transposon libraries. Overall, iRM23NL demonstrates a solid capability to predict cellular phenotypes and holds immense potential as a valuable resource for accurate predictions in advancing antimicrobial therapies. Moreover, it can guide metabolic engineering to tailor R. mucilaginosa's metabolism for desired performance.IMPORTANCECystic fibrosis (CF) is a genetic disorder characterized by thick mucosal secretions, leading to chronic lung infections. Rothia mucilaginosa is a common bacterium found in various parts of the human body, acting as a normal part of the flora. In people with weakened immune systems, it can become an opportunistic pathogen, while it is prevalent and active in CF airways. Recent studies have highlighted its anti-inflammatory properties in the lower pulmonary system, indicating the intricate relationship between microbes and human health. Herein, we have developed the first manually curated metabolic model of R. mucilaginosa. Our study examined the previously unknown relationships between the bacterium's genotype and phenotype and identified essential genes that impact the metabolism under various conditions. With this, we opt for paving the way for developing new strategies in antimicrobial therapy and metabolic engineering, leading to enhanced therapeutic outcomes in cystic fibrosis and related conditions.

Effect of Poly(Vinyl Pyrrolidone) on Iodine Release from Acrylate-Endcapped Urethane-Based Poly(Ethylene Glycol) Hydrogels as Antibacterial Wound Dressing.

Infections are still a major cause of morbidity in burn wounds. Although silver has been used strongly in past centuries as an anti-bacterial, it can lead to allergic reactions, bacterial resistance, and delayed wound healing. Iodine-based antibacterials are becoming an interesting alternative. In this work, the effect of complexation with poly(vinyl pyrrolidone) (PVP) and poly(ethylene oxide) (PEO)-based polymers is explored by using different acrylate-endcapped urethane-based poly(ethylene glycol) (AUP) polymers, varying the molar mass (MM) of the poly(ethylene glycol) (PEG) backbone, with possible addition of PVP. The higher MM AUP outperforms the swelling potential of commercial wound dressings such as Kaltostat, Aquacel Ag, and Hydrosorb and all MM show superior mechanical properties. The addition of iodine to the polymers is compared to Iso-Betadine Tulle (IBT). Interestingly, the addition of PVP does not lead to increased iodine complexation compared to the blank AUP polymers, while all have a prolonged iodine release compared to the IBT, which leads to a burst release. The observed prolonged release also leads to larger inhibition zones during antibacterial tests. Complexing iodine in AUP polymers with or without PVP leads to antimicrobial wound dressings which may hold potential for future application to treat infected wounds.

Pooling isolates to address the diversity in antimicrobial susceptibility of Pseudomonas aeruginosa in cystic fibrosis.

IMPORTANCE: People with cystic fibrosis (pwCF) often suffer from chronic lung infections with Pseudomonas aeruginosa. While antibiotics are still commonly used to treat P. aeruginosa infections, there is a high discordance between in vitro and in vivo antibiotic efficacy, which contributes to suboptimal antibiotic therapy. In the present study, we found that isolates from the same sputum sample had highly diverse antibiotic resistance profiles [based on the minimal inhibitory concentration (MIC)], which may explain the reported discrepancy between in vitro and in vivo antibiotic efficacy. Through systematic analysis, we report that pooling nine isolates per sputum sample significantly decreased intrasample diversity in MIC and influenced clinical interpretation of antibiotic susceptibility tests compared to single isolate testing. Hence, pooling of isolates may offer a solution to obtain a consistent MIC test result and could lead to optimizing antibiotic therapy in pwCF and other infectious diseases where diversity in antibiotic resistance is observed.

Effect of malate on the activity of ciprofloxacin against Pseudomonas aeruginosa in different in vivo and in vivo-like infection models.

The clinical significance of Pseudomonas aeruginosa infections and the tolerance of this opportunistic pathogen to antibiotic therapy makes the development of novel antimicrobial strategies an urgent need. We previously found that D,L-malic acid potentiates the activity of ciprofloxacin against P. aeruginosa biofilms grown in a synthetic cystic fibrosis sputum medium by increasing metabolic activity and tricarboxylic acid cycle activity. This suggested a potential new strategy to improve antibiotic therapy in P. aeruginosa infections. Considering the importance of the microenvironment on microbial antibiotic susceptibility, the present study aims to further investigate the effect of D,L-malate on ciprofloxacin activity against P. aeruginosa in physiologically relevant infection models, aiming to mimic the infection environment more closely. We used Caenorhabditis elegans nematodes, Galleria mellonella larvae, and a 3-D lung epithelial cell model to assess the effect of D,L-malate on ciprofloxacin activity against P. aeruginosa. D,L-malate was able to significantly enhance ciprofloxacin activity against P. aeruginosa in both G. mellonella larvae and the 3-D lung epithelial cell model. In addition, ciprofloxacin combined with D,L-malate significantly improved the survival of infected 3-D cells compared to ciprofloxacin alone. No significant effect of D,L-malate on ciprofloxacin activity against P. aeruginosa in C. elegans nematodes was observed. Overall, these data indicate that the outcome of the experiment is influenced by the model system used which emphasizes the importance of using models that reflect the in vivo environment as closely as possible. Nevertheless, this study confirms the potential of D,L-malate to enhance ciprofloxacin activity against P. aeruginosa-associated infections.

Biofilm antimicrobial susceptibility testing: where are we and where could we be going?

Our knowledge about the fundamental aspects of biofilm biology, including the mechanisms behind the reduced antimicrobial susceptibility of biofilms, has increased drastically over the last decades. However, this knowledge has so far not been translated into major changes in clinical practice. While the biofilm concept is increasingly on the radar of clinical microbiologists, physicians, and healthcare professionals in general, the standardized tools to study biofilms in the clinical microbiology laboratory are still lacking; one area in which this is particularly obvious is that of antimicrobial susceptibility testing (AST). It is generally accepted that the biofilm lifestyle has a tremendous impact on antibiotic susceptibility, yet AST is typically still carried out with planktonic cells. On top of that, the microenvironment at the site of infection is an important driver for microbial physiology and hence susceptibility; but this is poorly reflected in current AST methods. The goal of this review is to provide an overview of the state of the art concerning biofilm AST and highlight the knowledge gaps in this area. Subsequently, potential ways to improve biofilm-based AST will be discussed. Finally, bottlenecks currently preventing the use of biofilm AST in clinical practice, as well as the steps needed to get past these bottlenecks, will be discussed.

What's in a name? Characteristics of clinical biofilms.

In vitro biofilms are communities of microbes with unique features compared to individual cells. Biofilms are commonly characterized by physical traits like size, adhesion, and a matrix made of extracellular substances. They display distinct phenotypic features, such as metabolic activity and antibiotic tolerance. However, the relative importance of these traits depends on the environment and bacterial species. Various mechanisms enable biofilm-associated bacteria to withstand antibiotics, including physical barriers, physiological adaptations, and changes in gene expression. Gene expression profiles in biofilms differ from individual cells but, there is little consensus among studies and so far, a 'biofilm signature transcriptome' has not been recognized. Additionally, the spatial and temporal variability within biofilms varies greatly depending on the system or environment. Despite all these variable conditions, which produce very diverse structures, they are all noted as biofilms. We discuss that clinical biofilms may differ from those grown in laboratories and found in the environment and discuss whether the characteristics that are commonly used to define and characterize biofilms have been shown in infectious biofilms. We emphasize that there is a need for a comprehensive understanding of the specific traits that are used to define bacteria in infections as clinical biofilms.

3D-printed wound dressings containing a fosmidomycin-derivative prevent Acinetobacter baumannii biofilm formation.

Acinetobacter baumannii causes a wide range of infections, including wound infections. Multidrug-resistant A. baumannii is a major healthcare concern and the development of novel treatments against these infections is needed. Fosmidomycin is a repurposed antimalarial drug targeting the non-mevalonate pathway, and several derivatives show activity toward A. baumannii. We evaluated the antimicrobial activity of CC366, a fosmidomycin prodrug, against a collection of A. baumannii strains, using various in vitro and in vivo models; emphasis was placed on the evaluation of its anti-biofilm activity. We also developed a 3D-printed wound dressing containing CC366, using melt electrowriting technology. Minimal inhibitory concentrations of CC366 ranged from 1 to 64 µg/mL, and CC366 showed good biofilm inhibitory and moderate biofilm eradicating activity in vitro. CC366 successfully eluted from a 3D-printed dressing, the dressings prevented the formation of A. baumannnii wound biofilms in vitro and reduced A. baumannii infection in an in vivo mouse model.

Combining phages and antibiotic to enhance antibiofilm efficacy against an in vitro dual species wound biofilm.

Chronic wound management is extremely challenging because of the persistence of biofilm-forming pathogens, such as Pseudomonas aeruginosa and Staphylococcus aureus, which are the prevailing bacterial species that co-infect chronic wounds. Phage therapy has gained an increased interest to treat biofilm-associated infections, namely when combined with antibiotics. Here, we tested the effect of gentamicin as a co-adjuvant of phages in a dual species-biofilm wound model formed on artificial dermis. The biofilm-killing capacity of the tested treatments was significantly increased when phages were combined with gentamicin and applied multiple times as multiple dose (three doses, every 8 h). Our results suggest that gentamycin is an effective adjuvant of phage therapy particularly when applied simultaneously with phages and in three consecutive doses. The multiple and simultaneous dose treatment seems to be essential to avoid bacterial resistance development to each of the antimicrobial agents.

A systematic review of the use of bacteriophages for in vitro biofilm control.

Bacteriophages (phages) are very promising biological agents for the prevention and control of bacterial biofilms. However, little is known about the parameters that can influence the efficacy of phages on biofilms. This systematic review provides a summary and analysis of the published data about the use of phages to control pre-formed biofilms in vitro, suggesting recommendations for future experiments in this area. A total of 68 articles, containing data on 605 experiments addressing the efficacy of phages to control biofilms in vitro were included, after a search conducted in Web of Science, Embase, and Medline (PubMed). The data collected from each experiment included information about biofilm growth conditions, phage characteristics, treatment conditions and biofilm reduction. In most cases, biofilms were formed in the surface of microtiter plates (82.5%); the median time for biofilm formation was 24 h, as is the median treatment duration. Quantification of biofilm biomass (52.6%), viable cells (25.5%) and metabolic activity (17.9%) were the most common biofilm assessment methods. Correlation analysis revealed that some phage parameters can influence the treatment outcome: higher phage concentrations were strongly associated with improved biofilm control, leading to higher levels of biofilm reduction, and phages with higher burst sizes and shorter latent periods seem to be the best candidates to control biofilms in vitro. However, the great variability of the methodologies used prompts the need for the development of standardized in vitro methodologies to characterize phage/biofilm interactions and to assess the efficacy of phages to control biofilms.

In vitro and in vivo evaluation of diethyldithiocarbamate with copper ions and its liposomal formulation for the treatment of Staphylococcus aureus and Staphylococcus epidermidis biofilms.

Surgical site infections (SSIs) are mainly caused by Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis) biofilms. Biofilms are aggregates of bacteria embedded in a self-produced matrix that offers protection against antibiotics and promotes the spread of antibiotic-resistance in bacteria. Consequently, antibiotic treatment frequently fails, resulting in the need for alternative therapies. The present study describes the in vitro efficacy of the Cu(DDC)2 complex (2:1 M ratio of diethyldithiocarbamate (DDC-) and Cu2+) with additional Cu2+ against S. aureus and S. epidermidis biofilms in models mimicking SSIs and in vitro antibacterial activity of a liposomal Cu(DDC)2 + Cu2+ formulation. The in vitro activity on S. aureus and S. epidermidis biofilms grown on two hernia mesh materials and in a wound model was determined by colony forming unit (CFU) counting. Cu2+-liposomes and Cu(DDC)2-liposomes were prepared, and their antibacterial activity was assessed in vitro using the alamarBlue assay and CFU counting and in vivo using a Galleria mellonella infection model. The combination of 35 µM DDC- and 128 µM Cu2+ inhibited S. aureus and S. epidermidis biofilms on meshes and in a wound infection model. Cu(DDC)2-liposomes + free Cu2+ displayed similar antibiofilm activity to free Cu(DDC)2 + Cu2+, and significantly increased the survival of S. epidermidis-infected larvae. Whilst Cu(DDC)2 + Cu2+ showed substantial antibiofilm activity in vitro against clinically relevant biofilms, its application in mammalian in vivo models is limited by solubility. The liposomal Cu(DDC)2 + Cu2+ formulation showed antibiofilm activity in vitro and antibacterial activity and low toxicity in G. mellonella, making it a suitable water-soluble formulation for future application on infected wounds in animal trials.

The Small RNA NcS25 Regulates Biological Amine-Transporting Outer Membrane Porin BCAL3473 in Burkholderia cenocepacia.

Regulation of porin expression in bacteria is complex and often involves small-RNA regulators. Several small-RNA regulators have been described for Burkholderia cenocepacia, and this study aimed to characterize the biological role of the conserved small RNA NcS25 and its cognate target, outer membrane protein BCAL3473. The B. cenocepacia genome carries a large number of genes encoding porins with yet-uncharacterized functions. Expression of the porin BCAL3473 is strongly repressed by NcS25 and activated by other factors, such as a LysR-type regulator and nitrogen-depleted growth conditions. The porin is involved in transport of arginine, tyrosine, tyramine, and putrescine across the outer membrane. Porin BCAL3473, with NcS25 as a major regulator, plays an important role in the nitrogen metabolism of B. cenocepacia. IMPORTANCE Burkholderia cenocepacia is a Gram-negative bacterium which causes infections in immunocompromised individuals and in people with cystic fibrosis. A low outer membrane permeability is one of the factors giving it a high level of innate resistance to antibiotics. Porins provide selective permeability for nutrients, and antibiotics can also traverse the outer membrane by this means. Knowing the properties and specificities of porin channels is therefore important for understanding resistance mechanisms and for developing new antibiotics and could help in overcoming permeability issues in antibiotic treatment.

High throughput determination of the biofilm prevention concentration for Pseudomonas aeruginosa biofilms using a synthetic cystic fibrosis sputum medium.

The presence of Pseudomonas aeruginosa biofilms in cystic fibrosis (CF) patients suffering from chronic lung infections contributes to the failure of antimicrobial therapy. Conventionally, the minimal inhibitory concentration (MIC) is determined to assess the antimicrobial susceptibility of a pathogen, however this parameter fails to predict success in treating biofilm-associated infections. In the present study we developed a high throughput method to determine the antimicrobial concentration required to prevent P. aeruginosa biofilm formation, using a synthetic cystic fibrosis sputum medium (SCFM2). Biofilms were grown in SCFM2 for 24 h in the presence of antibiotics (tobramycin, ciprofloxacin or colistin), whereafter biofilms were disrupted and a resazurin staining was used to quantify the number of surviving metabolically active cells. In parallel, the content of all wells was plated to determine the number of colony forming units (CFU). Biofilm preventing concentrations (BPCs) were compared to MICs and minimal bactericidal concentrations (MBCs) determined according to EUCAST guidelines. Correlations between the resazurin-derived fluorescence and CFU counts were assessed with Kendall's Tau Rank tests. A significant correlation between fluorescence and CFU counts was observed for 9 out of 10 strains investigated, suggesting the fluorometric assay is a reliable alternative to plating for most P. aeruginosa isolates to determine biofilm susceptibility in relevant conditions. For all isolates a clear difference between MICs and BPCs of all three antibiotics was observed, with the BPCs being consistently higher than the MICs. Additionally, the extent of this difference appeared to be antibiotic-dependent. Our findings suggest that this high throughput assay could be a valuable addition to evaluate the antimicrobial susceptibility in P. aeruginosa biofilms in the context of CF.

Adaptation of Pseudomonas aeruginosa biofilms to tobramycin and the quorum sensing inhibitor C-30 during experimental evolution requires multiple genotypic and phenotypic changes.

In the present study we evaluated the fitness, antimicrobial susceptibility, metabolic activity, gene expression, in vitro production of virulence factors and in vivo virulence of experimentally evolved Pseudomonas aeruginosa PAO1. These strains were previously evolved in the presence of tobramycin and the quorum sensing inhibitor furanone C-30 (C-30) and carried mutations in mexT and fusA1. Compared to the wild-type (WT), the evolved strains show a different growth rate and different metabolic activity, suggesting they have an altered fitness. mexT mutants were less susceptible to C-30 than WT strains; they also show reduced susceptibility to chloramphenicol and ciprofloxacin, two substrates of the MexEF-OprN efflux pump. fusA1 mutants had a decreased susceptibility to aminoglycoside antibiotics, and an increased susceptibility to chloramphenicol. The decreased antimicrobial susceptibility and decreased susceptibility to C-30 was accompanied by a changed metabolic activity profile during treatment. The expression of mexE was significantly increased in mexT mutants and induced by C-30, suggesting that MexEF-OprN exports C-30 out of the bacterial cell. The in vitro production of virulence factors as well as virulence in two in vivo models of the strains evolved in the presence of C-30 was unchanged compared to the virulence of the WT. Finally, the evolved strains were less susceptible towards tobramycin (alone and combined with C-30) in an in vivo mouse model. In conclusion, this study shows that mutations acquired during experimental evolution of P. aeruginosa biofilms in the presence of tobramycin and C-30, are accompanied by an altered fitness, metabolism, mexE expression and in vitro and in vivo antimicrobial susceptibility.

Phenotypic Characterization and Heterogeneity among Modern Clinical Isolates of Acinetobacter baumannii.

Acinetobacter baumannii is an opportunistic pathogenic bacterium prioritized by WHO and CDC because of its increasing antibiotic resistance. Heterogeneity among strains represents the hallmark of A. baumannii bacteria. We wondered to what extent extensively used strains, so-called reference strains, reflect the dynamic nature and intrinsic heterogeneity of these bacteria. We analyzed multiple phenotypic traits of 43 nonredundant, modern, and multidrug-resistant, extensively drug-resistant, and pandrug-resistant clinical isolates and broadly used strains of A. baumannii. Comparison of these isolates at the genetic and phenotypic levels confirmed a high degree of heterogeneity. Importantly, we observed that a significant portion of modern clinical isolates strongly differs from several historically established strains in the light of colony morphology, cellular density, capsule production, natural transformability, and in vivo virulence. The significant differences between modern clinical isolates of A. baumannii and established strains could hamper the study of A. baumannii, especially concerning its virulence and resistance mechanisms. Hence, we propose a variable collection of modern clinical isolates that are characterized at the genetic and phenotypic levels, covering a wide range of the phenotypic spectrum, with six different macrocolony type groups, from avirulent to hypervirulent phenotypes, and with naturally noncapsulated to hypermucoid strains, with intermediate phenotypes as well. Strain-specific mechanistic observations remain interesting per se, and established "reference" strains have undoubtedly been shown to be very useful to study basic mechanisms of A. baumannii biology. However, any study based on a specific strain of A. baumannii should be compared to modern and clinically relevant isolates. IMPORTANCE Acinetobacter baumannii is a bacterium prioritized by the CDC and WHO because of its increasing antibiotic resistance, leading to treatment failures. The hallmark of this pathogen is the high heterogeneity observed among isolates, due to a very dynamic genome. In this context, we tested if a subset of broadly used isolates, considered "reference" strains, was reflecting the genetic and phenotypic diversity found among currently circulating clinical isolates. We observed that the so-called reference strains do not cover the whole diversity of the modern clinical isolates. While formerly established strains successfully generated a strong base of knowledge in the A. baumannii field and beyond, our study shows that a rational choice of strain, related to a specific biological question, should be taken into consideration. Any data obtained with historically established strains should also be compared to modern and clinically relevant isolates, especially concerning drug screening, resistance, and virulence contexts.

Acyloxymethyl and alkoxycarbonyloxymethyl prodrugs of a fosmidomycin surrogate as antimalarial and antibacterial agents.

Fosmidomycin is a natural antibiotic with potent IspC (DXR, 1-deoxy-d-xylulose-5-phosphate reductoisomerase) inhibitory activity. This enzyme catalyzes the first committed step of the non-mevalonate isoprenoid biosynthesis pathway, which is essential in most bacteria, including A. baumanii and M. tuberculosis, and apicomplexan parasites, including Plasmodium parasites. Mainly as a result of its high polarity, fosmidomycin displays suboptimal pharmacokinetic properties. Furthermore, fosmidomycin is inactive against A. baumannii and M. tuberculosis as a result of its inability to penetrate the bacterial cell wall. Temporarily masking the phosphonate moiety as a prodrug has the potential to solve both issues. We report on the expansion of the acyloxymethyl and alkoxycarbonyloxymethyl phosphonate ester prodrug series of a fosmidomycin surrogate. Prodrug promoieties were designed based on electronic, lipophilic and siderophoric properties. This investigation led to the discovery of derivatives with two-digit nanomolar and submicromolar IC50-values against P. falciparum and A. baumanii, respectively.

Sebaceous immunobiology - skin homeostasis, pathophysiology, coordination of innate immunity and inflammatory response and disease associations.

This review presents several aspects of the innovative concept of sebaceous immunobiology, which summarizes the numerous activities of the sebaceous gland including its classical physiological and pathophysiological tasks, namely sebum production and the development of seborrhea and acne. Sebaceous lipids, which represent 90% of the skin surface lipids in adolescents and adults, are markedly involved in the skin barrier function and perifollicular and dermal innate immune processes, leading to inflammatory skin diseases. Innovative experimental techniques using stem cell and sebocyte models have clarified the roles of distinct stem cells in sebaceous gland physiology and sebocyte function control mechanisms. The sebaceous gland represents an integral part of the pilosebaceous unit and its status is connected to hair follicle morphogenesis. Interestingly, professional inflammatory cells contribute to sebocyte differentiation and homeostasis, whereas the regulation of sebaceous gland function by immune cells is antigen-independent. Inflammation is involved in the very earliest differentiation changes of the pilosebaceous unit in acne. Sebocytes behave as potent immune regulators, integrating into the innate immune responses of the skin. Expressing inflammatory mediators, sebocytes also contribute to the polarization of cutaneous T cells towards the Th17 phenotype. In addition, the immune response of the perifollicular infiltrate depends on factors produced by the sebaceous glands, mostly sebaceous lipids. Human sebocytes in vitro express functional pattern recognition receptors, which are likely to interact with bacteria in acne pathogenesis. Sex steroids, peroxisome proliferator-activated receptor ligands, neuropeptides, endocannabinoids and a selective apoptotic process contribute to a complex regulation of sebocyte-induced immunological reaction in numerous acquired and congenital skin diseases, including hair diseases and atopic dermatitis.

Biofilm antimicrobial susceptibility through an experimental evolutionary lens.

Experimental evolution experiments in which bacterial populations are repeatedly exposed to an antimicrobial treatment, and examination of the genotype and phenotype of the resulting evolved bacteria, can help shed light on mechanisms behind reduced susceptibility. In this review we present an overview of why it is important to include biofilms in experimental evolution, which approaches are available to study experimental evolution in biofilms and what experimental evolution has taught us about tolerance and resistance in biofilms. Finally, we present an emerging consensus view on biofilm antimicrobial susceptibility supported by data obtained during experimental evolution studies.

New concepts in antimicrobial resistance in cystic fibrosis respiratory infections.

In this review, we summarize the main points that were raised and highlighted during the pre-conference meeting to the 17th European Cystic Fibrosis Society Basic Science Conference, held from 30 March to 2 April, 2022 in Albufeira, Portugal. Keynote lectures provided an update on the latest information regarding the phenomenon of antimicrobial resistance (AMR) in cystic fibrosis (CF). Traditional themes such as in vitro antibiotic susceptibility testing and its clinical value, AMR evolution in persistent Pseudomonas aeruginosa infection and the impact of biofilm on AMR were discussed. In addition, the report gives an overview on very recent AMR-related topics that include an ecological view of AMR in CF lung, referred to as resistome, and novel anti-infective approaches in preclinical or early clinical research such as antibiofilm drugs and bacteriophages.