Towards improved biofilm models.

Biofilms are complex microbial communities that have a critical function in many natural ecosystems, industrial settings as well as in recurrent and chronic infections. Biofilms are highly heterogeneous and dynamic assemblages that display complex responses to varying environmental factors, and those properties present substantial challenges for their study and control. In recent years, there has been a growing interest in developing improved biofilm models to offer more precise and comprehensive representations of these intricate systems.

Exploiting cooperative pathogen behaviour for enhanced antibiotic potency: A Trojan horse approach.

Antimicrobial resistance poses an escalating global threat, rendering traditional drug development approaches increasingly ineffective. Thus, novel alternatives to antibiotic-based therapies are needed. Exploiting pathogen cooperation as a strategy for combating resistant infections has been proposed but lacks experimental validation.

Exploiting Cooperative Pathogen Behavior for Enhanced Antibiotic Potency: A Trojan Horse Approach.

Antimicrobial resistance poses an escalating global threat, rendering traditional drug development approaches increasingly ineffective. Thus, novel alternatives to antibiotic-based therapies are needed. Exploiting pathogen cooperation as a strategy for combating resistant infections has been proposed but lacks experimental validation.

A Pseudomonas aeruginosa small RNA regulates chronic and acute infection.

The ability to switch between different lifestyles allows bacterial pathogens to thrive in diverse ecological niches. However, a molecular understanding of their lifestyle changes within the human host is lacking. Here, by directly examining bacterial gene expression in human-derived samples, we discover a gene that orchestrates the transition between chronic and acute infection in the opportunistic pathogen Pseudomonas aeruginosa.

Perspective: The viscoelastic properties of biofilm infections and mechanical interactions with phagocytic immune cells.

Biofilms are viscoelastic materials that are a prominent public health problem and a cause of most chronic bacterial infections, in large part due to their resistance to clearance by the immune system. Viscoelastic materials combine both solid-like and fluid-like mechanics, and the viscoelastic properties of biofilms are an emergent property of the intercellular cohesion characterizing the biofilm state (planktonic bacteria do not have an equivalent property). However, how the mechanical properties of biofilms are related to the recalcitrant disease that they cause, specifically to their resistance to phagocytic clearance by the immune system, remains almost entirely unstudied.

Microrheology of Pseudomonas aeruginosa biofilms grown in wound beds.

A new technique was used to measure the viscoelasticity of in vivo Pseudomonas aeruginosa biofilms. This was done through ex vivo microrheology measurements of in vivo biofilms excised from mouse wound beds. To our knowledge, this is the first time that the mechanics of in vivo biofilms have been measured.

Contribution of Exopolysaccharides Pel and Psl to Wound Infections.

Biofilms are the cause of most chronic bacterial infections. Living within the biofilm matrix, which is made of extracellular substances, including polysaccharides, proteins, eDNA, lipids and other molecules, provides microorganisms protection from antimicrobials and the host immune response. Exopolysaccharides are major structural components of bacterial biofilms and are thought to be vital to numerous aspects of biofilm formation and persistence, including adherence to surfaces, coherence with other biofilm-associated cells, mechanical stability, protection against desiccation, binding of enzymes, and nutrient acquisition and storage, as well as protection against antimicrobials, host immune cells and molecules, and environmental stressors.

Efficacy and safety of biofilm dispersal by glycoside hydrolases in wounds.

Novel anti-biofilm and dispersal agents are currently being investigated in an attempt to combat biofilm-associated wound infections. Glycoside hydrolases (GHs) are enzymes that hydrolyze the glycosidic bonds between sugars, such as those found within the exopolysaccharides of the biofilm matrix. Previous studies have shown that GHs can weaken the matrix, inducing bacterial dispersal, and improving antibiotic clearance.

Lysis-Hi-C as a method to study polymicrobial communities and eDNA.

Microbes interact in natural communities in a spatially structured manner, particularly in biofilms and polymicrobial infections. While next generation sequencing approaches provide powerful insights into diversity, metabolic capacity, and mutational profiles of these communities, they generally fail to recover in situ spatial proximity between distinct genotypes in the interactome. Hi-C is a promising method that has assisted in analysing complex microbiomes, by creating chromatin cross-links in cells, that aid in identifying adjacent DNA, to improve de novo assembly.

The importance of understanding the infectious microenvironment.

Standard doses of antibiotics do not efficiently treat chronic infections of the soft tissue and bone. In this Personal View, we advocate for improving treatment of these infections by taking the infectious microenvironment into account. The infectious microenvironment can cause sensitive bacteria to lose their susceptibility to antibiotics that are effective in standard laboratory susceptibility testing.

Assessing Biofilm Dispersal in Murine Wounds.

Biofilm-related infections are implicated in a wide array of chronic conditions such as non-healing diabetic foot ulcers, chronic sinusitis, reoccurring otitis media, and many more. Microbial cells within these infections are protected by an extracellular polymeric substance (EPS), which can prevent antibiotics and host immune cells from clearing the infection. To overcome this obstacle, investigators have begun developing dispersal agents as potential therapeutics.

Effect of collagen and EPS components on the viscoelasticity of biofilms.

Pseudomonas aeruginosa is an opportunistic pathogen that causes thousands of deaths every year in part due to its ability to form biofilms composed of bacteria embedded in a matrix of self-secreted extracellular polysaccharides (EPS), e-DNA, and proteins. In chronic wounds, biofilms are exposed to the host extracellular matrix, of which collagen is a major component. How bacterial EPS interacts with host collagen and whether this interaction affects biofilm viscoelasticity is not well understood.

Detection of bacterial fluorescence from in vivo wound biofilms using a point-of-care fluorescence imaging device.

Wound biofilms must be identified to target disruption and bacterial eradication but are challenging to detect with standard clinical assessment. This study tested whether bacterial fluorescence imaging could detect porphyrin-producing bacteria within a biofilm using well-established in vivo models. Mouse wounds were inoculated on Day 0 with planktonic bacteria (n = 39, porphyrin-producing and non-porphyrin-producing species, 10  colony forming units (CFU)/wound) or with polymicrobial biofilms (n = 16, 3 biofilms per mouse, each with 1:1:1 parts Staphylococcus aureus/Escherichia coli/Enterobacter cloacae, 10  CFU/biofilm) that were grown in vitro.

Utilizing glycoside hydrolases to improve the quantitation and visualization of biofilm bacteria.

The complexity of microbial biofilms offers several challenges to the use of traditional means of microbial research. In particular, it can be difficult to calculate accurate numbers of biofilm bacteria, because even after thorough homogenization or sonication, small pieces of the biofilm remain, which contain numerous bacterial cells and result in inaccurately low colony forming units (CFU). In addition, imaging of infected tissue often results in a disparity between the CFU and the number of bacterial cells observed under the microscope.

How well are we translating biofilm research from bench-side to bedside?

Biofilms are responsible for more than 80% of all chronic infections and represent an enormous medical challenge. In order to meet this challenge, translation research on anti-biofilm approaches is desperately needed. While biofilm research has grown exponentially over the last three decades and provided important details about the mechanisms involved in initiating, maintaining and disrupting bacterial communities, how much of this basic science knowledge has resulted in new therapeutic approaches? In this perspective article biofilm publications, patents, clinical trials and companies were surveyed to ascertain where we stand in translating biofilm research into new strategies to treat and prevent biofilm-associated infections.

Persistence and progression of staphylococcal infection in the presence of public goods.

Staphylococcus aureus is a prominent etiological agent of suppurative abscesses. In principle, abscess formation and purulent exudate are classical physiological features of healing and tissue repair. However, S.

The evolution of virulence in during chronic wound infection.

Opportunistic pathogens are associated with a number of chronic human infections, yet the evolution of virulence in these organisms during chronic infection remains poorly understood. Here, we tested the evolution of virulence in the human opportunistic pathogen in a murine chronic wound model using a two-part serial passage and sepsis experiment, and found that virulence evolved in different directions in each line of evolution. We also assessed adaptation to a chronic wound after 42 days of evolution and found that morphological diversity in our evolved populations was limited compared with that previously described in cystic fibrosis (CF) infections.

The safety profile of Bald's eyesalve for the treatment of bacterial infections.

The rise in antimicrobial resistance has prompted the development of alternatives to combat bacterial infections. Bald's eyesalve, a remedy used in the Early Medieval period, has previously been shown to have efficacy against Staphylococcus aureus in in vitro and in vivo models of chronic wounds. However, the safety profile of Bald's eyesalve has not yet been demonstrated, and this is vital before testing in humans.