Survival strategies of infectious biofilms

Bacteria-triggered on-demand thymol release for salmon preservation: A self-destructive antibacterial strategy

To prevent foodborne pathogen invasion in fresh meat during storage, this study develops an enzyme/redox dual-responsive nanomaterial (Thy@MSN-S-S-Casein). Upon encountering bacteria, the casein shell is degraded by bacterial proteases, and glutathione (GSH) cleaves the disulfide bonds on the mesoporous silica nanoparticle (MSN) surface, releasing thymol to combat the bacteria. Trypsin and GSH triggered a cumulative release of 68.37 % thymol from Thy@MSN-S-S-Casein within 48 h, which was significantly higher than the release by trypsin alone (49.93 %) or without any activation (17.33 %). The antibacterial activities of Thy@MSN-S-S-Casein can be triggered by both artificially inoculated bacteria and naturally-infected bacteria on the salmon surfaces, leading to a reduction in the total viable count (TVC) in both experiments. Additionally, it inhibited the deterioration of the salmon fillets' quality indicators and extended their shelf life by about 3 days. This bacteria-triggered release strategy offers a promising self-destructive antibacterial approach for mitigating pathogen outbreaks in food preservation.

Comprehensive strategies for overcoming dental biofilms: Microbial dynamics and innovative methods

Dental biofilm develops through a complex process initiated by the attachment of early colonising bacteria to the surface of teeth. These bacteria use specific adhesion molecules to bind to the enamel, after which they proliferate and secrete an extracellular polymeric substance. As a result, the early colonisers eventually form a resilient, multispecies community encased in an extracellular polymeric matrix, reinforcing the biofilm structure. This matrix enables microbes to withstand the mechanical disruption, evade host immune defences and resist many antimicrobials. Diseases associated with dental biofilm are among the most prevalent oral health issues, highlighting the importance of effective biofilm management in maintaining oral health. This review explores the progression of biofilm development and evaluates various strategies, from conventional antibiotics and herbal medicine to advanced strategies like antimicrobial peptides, nanoparticles, probiotics, cold atmospheric plasma, quorum sensing inhibitors and enzymes. In particular, enzymatic agents such as Dispersin B, DNAases, and glucanohydrolases, including mutanase and dextranase, have shown promise in disrupting the biofilm structure, thereby offering potential avenues for managing dental biofilm.

Selective pressures for public antibiotic resistance

The rapid increase of antibiotic-resistant pathogens is severely limiting our current treatment possibilities. An important subset of the resistance mechanisms conferring antibiotic resistance have public effects, allowing otherwise susceptible bacteria to also survive antibiotic treatment. As susceptible bacteria can survive treatment without bearing the metabolic cost of producing the resistance mechanism, there is potential to increase their relative frequency in the population and, as such, select against resistant bacteria. Multiple studies showed that this altered selection for resistance is dependent on various environmental and treatment parameters. In this review, we provide a comprehensive overview of their most important findings and describe the main factors impacting the selection for resistance. In-depth understanding of the driving forces behind selection can aid in the design and implementation of alternative treatments which limit the risk of resistance development.

Inhibitory effects of reumycin produced by Streptomyces sp. TPMA0082 on virulence factors of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen that causes a wide range of infections. The increasing multidrug-resistance of P. aeruginosa poses a critical challenge for medical care. P. aeruginosa employs virulence factors and biofilms to establish infections in humans and protect itself from environmental stress or antibiotics. These factors are regulated by a quorum sensing mechanism involving multiple regulatory systems that act interdependently through signaling molecules. Therefore, interference with quorum sensing systems can suppress the pathogenicity of P. aeruginosa. In this study, quorum sensing inhibitors were explored from secondary metabolites derived from 111 strains of actinomycetes by targeting the las system, which is thought to be upstream of the quorum sensing cascade in P. aeruginosa. As a result, reumycin was isolated from the culture broth of Streptomyces sp. TPMA0082. Reumycin, a molecule containing a pyrimidotriazine ring, inhibited the binding of the autoinducer to the LasR receptor in the las system, thereby suppressing the production of P. aeruginosa virulence factors, including pyocyanin, rhamnolipids, elastase, motility, and biofilms, without affecting bacterial growth. Toxoflavin, a reumycin derivative with a methyl group at the N1 position, exhibited strong antibacterial activity. Fervenulin, a reumycin derivative with a methyl group at the N8 position, had a negative impact on the logarithmic growth phase of the bacteria and exhibited lower inhibitory activity against virulence factor production compared to reumycin. These findings suggest that the position and number of methyl groups attached to the pyrimidotriazine structure significantly influence its biological activity, exerting distinct effects on quorum sensing inhibition and antibacterial activity.

Carbon-Based Nanomaterials Alter the Behavior and Gene Expression Patterns of Bacteria

One of the most dangerous characteristics of bacteria is their propensity to form biofilms and their resistance to the drugs used in clinical practice today. The total number of genes that can be categorized as virulence genes ranges from a few hundred to more than a thousand. The bacteria employ a variety of mechanisms to regulate the expression of these genes in a coordinated manner during infection. The search for new agents with anti-virulence capacity is therefore crucial. Nanotechnology provides safe platforms for targeted therapies to combat a broad spectrum of microbial infections. As a new class of innovative materials, carbon-based nanomaterials (CBNs), which include carbon dots, carbon nanotubes, graphene, and fullerenes can have strong antibacterial activity. Exposure to CBNs has been shown to affect bacterial gene expression patterns. This study investigated the effect of CBNs on the repression of specific genes related to bacterial virulence/pathogenicity.

Effectiveness of sanitizers on different biofilm-forming microorganisms associated with the poultry drinking water system

The sanitation of the poultry drinking water system (DWS) is essential to controlling pathogens and biofilms in the DWS. Intervention approaches including several sanitizers have been developed, but there is limited information on the efficacy of some of these sanitizers. The aim of this study was to evaluate the effectiveness of peracid-based (PAB), peroxide-based (PB), and hypochlorite-based (HB) sanitizers against field-isolated Salmonella (10), E. coli (2) and Bacillus (2), along with their antibiofilm effects on six of these bacterial strains on polyvinylchloride (PVC), a common DWS pipe material. The minimum inhibitory and bactericidal concentrations (MIC and MBC) were determined using the microdilution broth method. For biofilm production, PVC rings were inoculated (5-6 Log10 CFU/mL) in buffered peptone water, incubated at 30°C for 48 h, and detached with cotton swabs for quantification. The antibiofilm effect of the sanitizers was further assessed at MIC, 2X-MIC, 4X-MIC, and water (control). Data was analyzed using ANOVA and Least squares in JMP Pro 18. The MIC and MBC of PAB for all isolates ranged from 11.36 to 28.42 ppm, PB from 15.26 to 71.21 ppm, and HB was 106.67 to 350 ppm. Bacillus licheniformis formed the most biofilm (5.39 Log10 CFU/mL) as single-species bacteria while Salmonella attached more (6.36 Log10 CFU/mL) than E. coli (5.41 Log10 CFU/mL) and Bacillus (2.08 Log10 CFU/mL) when grown together in mixed cultures. PAB and HB eliminated the biofilms of all strains tested at MIC in mixed-species cultures while PB had no significant effect. Overall, PAB demonstrated the greatest potential as a DWS sanitizer, showing superior efficacy against planktonic and biofilm cells compared to PB and HB. This research highlights the importance of targeted microbial profiling and sanitizer efficacy testing for pre-harvest pathogen control, providing valuable insights for enhancing food safety in poultry production systems.

Extracellular adherence proteins reduce matrix porosity and enhance Staphylococcus aureus biofilm survival during prosthetic joint infection

Biofilms are a cause of chronic, non-healing infections. Staphylococcus aureus is a proficient biofilm-forming pathogen commonly isolated from prosthetic joint infections that develop following primary arthroplasty. Extracellular adherence protein (Eap), previously characterized in planktonic or non-biofilm populations as being an adhesin and immune evasion factor, was recently identified in the exoproteome of S. aureus biofilms. This work demonstrates that Eap and its two functionally orphaned homologs EapH1 and EapH2 contribute to biofilm structure and prevent macrophage invasion and phagocytosis in these communities. Biofilms unable to express Eap proteins demonstrated increased porosity and reduced biomass. We describe the role of Eap proteins in vivo using a mouse model of S. aureus prosthetic joint infection. The Results suggest that the protection conferred to biofilms by Eap proteins is a function of biofilm structural stability that interferes with the leukocyte response to biofilm-associated bacteria.

Biofilm-mediated bioremediation of xenobiotics and heavy metals: a comprehensive review of microbial ecology, molecular mechanisms, and emerging biotechnological applications

Environmental pollution, driven by rapid industrialization and urbanization, has emerged as a critical global challenge in the twenty-first century. This comprehensive review explores the potential of bacterial biofilms in bioremediation, focusing on their ability to degrade and transform a wide array of pollutants, including heavy metals, persistent organic pollutants (POPs), oil spills, pesticides, and emerging contaminants, such as pharmaceuticals and microplastics. The unique structural and functional characteristics of biofilms, including their extracellular polymeric substance (EPS) matrix, enhanced genetic exchange, and metabolic cooperation, contribute to their superior pollutant degradation capabilities compared to planktonic bacteria. Recent advancements in biofilm-mediated bioremediation include the application of genetically engineered microorganisms, nanoparticle-biofilm interactions, and innovative biofilm reactor designs. The CRISPR-Cas9 system has shown promise in enhancing the degradative capabilities of biofilm-forming bacteria while integrating nanoparticles with bacterial biofilms demonstrates significant improvements in pollutant degradation efficiency. As global pollution rises, biofilm-based bioremediation emerges as a cost-effective and environmentally friendly approach to address diverse contaminants. This review signifies the need for further research to optimize these techniques and harness their full potential in addressing pressing environmental challenges.

Functional hydrogels promote chronic infectious wound healing by re-rousing macrophage M1 and inducing bacterial copper-like death

Traditional antibiotics are often ineffective against biofilm-associated infections, and biofilm-induced macrophage immune evasion directly halts the wound healing process. Disrupting biofilms and regulating macrophage immune functions are critical to improving wound healing. In this study, we synthesized g-C3N4 with peroxidase (POD) enzyme activity via thermal polymerization and copper alginate microspheres (CAM) via gas cutting. These were co-encapsulated into GelMA hydrogels to form a functionalized wound repair system (GelMA/CAM@g-C3N4) with both anti-biofilm and local immune microenvironment remodeling capabilities. In vitro, this system exhibited excellent biocompatibility and promoted endothelial cell migration, vascular formation, and CD31 expression. It also polarized macrophages toward the M1 phenotype, restoring their pro-inflammatory functions, upregulating inflammatory cytokines (IL-1, IL-6, TNF-α), and inhibiting Staphylococcus aureus and Escherichia coli. In vivo, the system suppressed S. aureus growth, promoted angiogenesis and collagen deposition, and reshaped the pathological microenvironment to achieve wound repair and regeneration. Conclusions: This system offers a new therapeutic strategy for chronic infectious wounds.

Encounter rates and engagement times limit the transmission of conjugative plasmids

Plasmid conjugation is a major route for the dissemination of antibiotic resistances and adaptive genes among bacterial populations. Obtaining precise conjugation rates is thus key to understanding how antibiotic resistances spread. Plasmid conjugation is typically modeled as a density-dependent process, where the formation of new transconjugants depends on the rate of encounters between donor and receptor cells. By analyzing conjugation dynamics at different cell concentrations, here we show that this assumption only holds at very low bacterial densities. At higher cell concentrations, conjugation becomes limited by the engagement time, the interval required between two successful matings. Plasmid conjugation therefore follows a Holling´s Type II functional response, characterized by the encounter rate and the engagement time, which represent, respectively, the density and frequency-dependent limits of plasmid transmission. Our results demonstrate that these parameters are characteristic of the transfer machinery, rather than the entire plasmid genome, and that they are robust to environmental and transcriptional perturbation. Precise parameterization of plasmid conjugation will contribute to better understanding the propagation dynamics of antimicrobial resistances.

Development of Synthetic Antimicrobial Peptides Based on Genomic Analysis of Streptococcus salivarius

BACKGROUND

In the oral environment, the production of bacteriocins or antimicrobial peptides (AMPs) plays a crucial role in maintaining ecological balance by impeding the proliferation of closely related microorganisms. This study aims to conduct in silico genome screening of Streptococcus salivarius to identify potential antimicrobial compounds existing as hypothetical peptides, with the goal of developing novel synthetic antimicrobial peptides.

METHODS

Draft genomes of various oral Streptococcus salivarius strains were obtained from the NCBI database and subjected to analysis using bioinformatic tools, viz. Expert Protein-Analysis System (Expasy), UniProt Knowledgebase (UniProtKB), European Molecular Biology Open Software Suite (EMBOSS), Pepwheel, and PEP-FOLD Peptide Structure Prediction Server. The antimicrobial potential of peptides was assessed through the Antimicrobial Peptide Database (AMP) and Bactibase. Two short peptides, viz. synthetic antimicrobial peptides (SAMPs), were designed based on current knowledge of hydrophobic and cationic residues, synthesized, and their efficacy against biofilm formation was evaluated with standard microbiological methods.

RESULTS

The synthesized short peptides reduced the growth and effectively inhibited biofilm formation by specific oral microbial strains, demonstrating their potential as antimicrobial peptides. Furthermore, the alignment of bacteriocin biosynthetic clusters among streptococcus strains revealed variations in putative bacteriocin amino acid sequences across different strains of the same organism.

CONCLUSION

Streptococcus salivarius emerges as a promising bioresource for the development of novel antimicrobial agents, particularly for combating biofilm-associated oral infections.

CAM/TMA-DPH as a promising alternative to SYTO9/PI for cell viability assessment in bacterial biofilms

Introduction

Accurately assessing biofilm viability is essential for evaluating both biofilm formation and the efficacy of antibacterial treatments. Traditional SYTO9 and propidium iodide (PI) live/dead staining in biofilm viability assays often ace challenges due to non-specific staining, limiting precise differentiation between live and dead cells. To address this limitation, we investigated an alternative staining method employing calcein acetoxymethyl (CAM) to detect viable cells based on esterase activity, and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) to assess the remaining biofilm population.

Methods

Biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecium were matured and exposed to varying concentrations of antibiotics or sterile medium. Biofilm viability was assessed using CAM/TMA-DPH or SYTO9/PIstaining, followed by analysis with confocal laser scanning microscopy (CLSM) and ImageJ-based biofilm surface coverage quantification. Viability findings were compared with colony-forming units (CFU/mL), a standard microbial viability measure.

Results

CAM/TMA-DPH staining demonstrated strong positive correlations with CFU counts across all bacterial species (r = 0.59 - 0.91), accurately reflecting biofilm vitality. In contrast, SYTO9/PI staining consistently underestimated the viability of untreated biofilms, particularly in Klebsiella pneumoniae, where a negative correlation with CFU/mL was observed (r = -0.04). Positive correlations for SYTO9/PI staining were noted in other species (r = 0.65 - 0.79). These findings underscore the limitations of membrane integrity-based staining methods and highlight the advantages of metabolic-based probes like CAM/TMA-DPH.

Discussion

Our findings suggest that CAM/TMA-DPH staining provides a promising alternative to SYTO9/PI for cell viability assessment in bacterial biofilms, highlighting the advantages of metabolic-based probes over traditional membrane integrity assays. The consistency of CAM/TMA-DPH staining across different bacterial species underscores its potential to advance studies on biofilm and contribute to the development of more effective anti-biofilm treatments, which is essential for clinical management of biofilm-associated infections.

An eco-evolutionary perspective on antimicrobial resistance in the context of One Health

The One Health approach musters growing concerns about antimicrobial resistance due to the increased use of antibiotics in healthcare and agriculture, with all of its consequences for human, livestock, and environmental health. In this perspective, we explore the current knowledge on how interactions at different levels of biological organization, from genetic to ecological interactions, affect the evolution of antimicrobial resistance. We discuss their role in different contexts, from natural systems with weak selection, to human-influenced environments that impose a strong pressure toward antimicrobial resistance evolution. We emphasize the need for an eco-evolutionary approach within the One Health framework and highlight the importance of horizontal gene transfer and microbiome interactions for increased understanding of the emergence and spread of antimicrobial resistance.

Clonality and the Phenotype-Genotype Correlation of Antimicrobial Resistance in Acinetobacter baumannii Isolates: A Multicenter Study of Clinical Isolates from Romania

Antibiotic resistance is on the WHO's top 10 list of global public health threats due to its rapid emergence and spread but also because of the high morbidity and mortality associated with it. Amongst the main species driving this phenomenon is A. baumannii, a member of the ESKAPE group of medical assistance-associated infections causing species famous for its extensively drug-resistant phenotypes. Our findings note a 91.52% frequency of extensively drug-resistant carbapenem-resistant A. baumannii (XDR CRAB) phenotype amongst clinical isolates from multiple hospitals in two major cities from northwestern and central Romania, harboring multiple antibiotic resistance genes such as blaOXA-23-like in 108 (91.5%) isolates, blaOXA-24/40-like in 88 (74.6%) isolates, blaNDM in 29 (25%) isolates, ArmA in 75 (63.6%) isolates, and ant(3″)-I in 69 (58.5%) isolates and sul1 in 113 (95.76%) isolates. The isolates, although nearly identical in phenotype, displayed different genotypical profiles, with varying degrees of similarity across hospitals and cities, raising the possibility of both local outbreaks of a single clone and widespread dissemination of resistant isolates.

Matrix porosity is associated with Staphylococcus aureus biofilm survival during prosthetic joint infection

Biofilms are a cause of chronic, non-healing infections. Staphylococcus aureus is a proficient biofilm forming pathogen commonly isolated from prosthetic joint infections that develop following primary arthroplasty. Extracellular adhesion protein (Eap), previously characterized in planktonic or non-biofilm populations as being an adhesin and immune evasion factor, was recently identified in the exoproteome of S. aureus biofilms. This work demonstrates that Eap and its two functionally orphaned homologs EapH1 and EapH2, contribute to biofilm structure and prevent macrophage invasion and phagocytosis into these communities. Biofilms unable to express Eap proteins demonstrated increased porosity and reduced biomass. We describe a role for Eap proteins in vivo using a mouse model of S. aureus prosthetic joint infection. Results suggest that the protection conferred to biofilms by Eap proteins is a function of biofilm structural stability that interferes with the leukocyte response to biofilm-associated bacteria.

Pathogen-encoded Rum DNA polymerase drives rapid bacterial drug resistance

The acquisition of multidrug resistance by pathogenic bacteria is a potentially incipient pandemic. Horizontal transfer of DNA from mobile integrative conjugative elements (ICEs) provides an important way to introduce genes that confer antibiotic (Ab)-resistance in recipient cells. Sizable numbers of SXT/R391 ICEs encode a hypermutagenic Rum DNA polymerase (Rum pol), which has significant homology with Escherichia coli pol V. Here, we show that even under tight transcriptional and post-transcriptional regulation imposed by host bacteria and the R391 ICE itself, Rum pol rapidly accelerates development of multidrug resistance (CIPR, RifR, AmpR) in E. coli in response to SOS-inducing Ab and non-Ab external stressors bleomycin (BLM), ciprofloxacin (CIP) and UV radiation. The impact of Rum pol on the rate of acquisition of drug resistance appears to surpass potential contributions from other cellular processes. We have shown that RecA protein plays a central role in controlling the ability of Rum pol to accelerate antibiotic resistance. A single amino acid substitution in RecA, M197D, acts as a 'Master Regulator' that effectively eliminates the Rum pol-induced Ab resistance. We suggest that Rum pol should be considered as one of the major factors driving development of de novo Ab resistance in pathogens carrying SXT/R391 ICEs.

Molecular characterization of Klebsiella pneumoniae in clinical bovine mastitis in 14 provinces in China

The mastitis caused by Klebsiella pneumoniae (K. pneumoniae) is increasing in the dairy cows. To investigate the epidemic of K. pneumoniae of China, 131 strains were isolated from 495 clinical mastitis milk samples (26.5%) from 14 provinces in China. Among the isolates, K57 was the dominant serotype (45.0%) and 19 (14.5%) isolates were identified as hypervirulent K. pneumoniae (hvKP). The mrkA, entB, wabG and fimH genes were prevalent virulence genes while rmpA, magA, and ycf were not found in K. pneumoniae. Furthermore, K. pneumoniae had serious antibiotic resistance and multiple β-lactamase genes, including blaTEM, blaSHV, blaNDM, blaCTX-M, blaDHA, and blaKPC. Biofilm was an important factor in bacterial resistance and persistent infection, and 77.1% isolates could form biofilm. Although acylated homoserine lactone (AHL, a Gram-negative bacterial quorum sensing signal molecule) was not confirmed among the K. pneumoniae isolates, exogenous AHLs could reduce the biofilm formation ability of the K. pneumoniae strains. Three new ST types (ST6781, ST6782, and ST6783) were first identified in this study. The MLST phylogenetic tree showed the distribution of mastitis associated K. pneumoniae strains had no regular pattern, which confirmed high genomic diversity of mastitis associated K. pneumoniae. In conclusion, the high rate of isolation and serious antibiotic resistance of K. pneumonia were found in this study and indicated a potential threat to public health from the food chain.

Co-existence of antibiotic resistance and virulence factors in carbapenem resistant Klebsiella pneumoniae clinical isolates from Alexandria, Egypt

BACKGROUND

The emergence and spread of carbapenem resistance among Enterobacteriaceae, particularly Klebsiella pneumoniae, constitute a serious threat to public health, since carbapenems are the last line of defense in the treatment of life-threatening infections caused by drug-resistant Enterobacteriaceae. The current study investigated the co-existence of different virulence factors and carbapenemases in carbapenem-resistant Klebsiella pneumoniae clinical isolates from Alexandria, Egypt.

RESULTS

Phenotypic characterization of virulence factors indicated that 41.5% of the isolates were strong biofilm producers, while hypermucoviscosity was detected in 14.9% of the isolates. All isolates harbored five or more virulence factor encoding genes. entB, ycfM, mrkD and fimH were detected in all isolates, while only one isolate was negative for ybtS. uge, iutA, rmpA and kpn were detected in 61 (64.8%), 55 (58.5%), 41 (43.6%) and 27 (28.7%) isolates, respectively, while all isolates lacked magA and k2A. Phenotypic detection of carbapenemases was explored by performing CarbaNP and mCIM/eCIM. CarbaNP test showed positive results in 98.9% of the isolates and positive mCIM tests were observed in all isolates, while 68 (72.3%) isolates showed positive eCIM tests. blaNDM was the most prevalent carbapenemase encoding gene (92.5%) followed by the blaOXA-48 (51.1%), while blaKPC was detected in only one (1.06%) isolate. blaVIM, blaIMP and blaGES were not detected in any of the tested isolates.

CONCLUSIONS

The widespread of carbapenem-resistant Klebsiella pneumoniae represents a major problem in health care settings. A significant association between certain virulence factors and carbapenemase-encoding genes was observed. Antibiotic stewardship programs and infection control policies should be effectively implemented especially in hospitals to limit the spread of such highly virulent pathogens.

Biofilm Production in Intensive Care Units: Challenges and Implications

The prevalence of infections amongst intensive care unit (ICU) patients is inevitably high, and the ICU is considered the epicenter for the spread of multidrug-resistant bacteria. Multiple studies have focused on the microbial diversity largely inhabiting ICUs that continues to flourish despite treatment with various antibiotics, investigating the factors that influence the spread of these pathogens, with the aim of implementing sufficient monitoring and infection control methods. Despite joint efforts from healthcare providers and policymakers, ICUs remain a hub for healthcare-associated infections. While persistence is a unique strategy used by these pathogens, multiple other factors can lead to persistent infections and antimicrobial tolerance in the ICU. Despite the recognition of the detrimental effects biofilm-producing pathogens have on ICU patients, overcoming biofilm formation in ICUs continues to be a challenge. This review focuses on various facets of ICUs that may contribute to and/or enhance biofilm production. A comprehensive survey of the literature reveals the apparent need for additional molecular studies to assist in understanding the relationship between biofilm regulation and the adaptive behavior of pathogens in the ICU environment. A better understanding of the interplay between biofilm production and antibiotic resistance within the environmental cues exhibited particularly by the ICU may also reveal ways to limit biofilm production and indivertibly control the spread of antibiotic-resistant pathogens in ICUs.

Biofilm of Cutibacterium acnes: a target of different active substances

BACKGROUND

Acne vulgaris is a chronic inflammatory dermatosis. Cutibacterium acnes plays a crucial role in the acne pathophysiology. Recent works present evidence of C. acnes growing as a biofilm in cutaneous follicles. This development is currently considered one of the leading causes of C. acnes in vivo persistence and resistance to antimicrobials used to treat acne.

OBJECTIVE

Our objective was to evaluate the effects of various active compounds (clindamycin, erythromycin, doxycycline, and myrtle extract) on eight distinct, well-characterized strains of C. acnes following their growth in biofilm mode.

METHODS/RESULTS

Cutibacterium acnes isolates from phylotypes IA1 and IA2 produce more biofilm than other phylotypes. No antibiotic effect was observed either during the curative test or preventive test. Myrtle extract at 0.01% (w/v) showed significant efficacy on the biofilm for C. acnes strains (curative assays). Furthermore, it appear that myrtle extract and doxycycline together reduce the overall biomass of the biofilm. A significant dose-dependent effect was observed during the preventive test, greater than the one observed under curative conditions, with an important loss of activity of the myrtle extract observed from 0.001% (w/v) concentration onwards. Transmission electron microscopy showed that bacteria treated with myrtle extract grew biofilms much less frequently than untreated bacteria. Additionally, when the quantity of myrtle extract grew, the overall number of bacteria dropped, indicating an additional antibacterial action.

CONCLUSION

These findings support the hypothesis that the different C. acnes phylotypes have various aptitudes in forming biofilms. They also suggest that myrtle extract is a promising alternative as an anti-biofilm and antibacterial agent in fighting diseases caused by planktonic and biofilm C. acnes.

Metabolic interactions control the transfer and spread of plasmid-encoded antibiotic resistance during surface-associated microbial growth

Surface-associated microbial systems are hotspots for the spread of plasmid-encoded antibiotic resistance, but how surface association affects plasmid transfer and proliferation remains unclear. Surface association enables prolonged spatial proximities between different populations, which promotes plasmid transfer between them. However, surface association also fosters strong metabolic interactions between different populations, which can direct their spatial self-organization with consequences for plasmid transfer and proliferation. Here, we hypothesize that metabolic interactions direct the spatial self-organization of different populations and, in turn, regulate the spread of plasmid-encoded antibiotic resistance. We show that resource competition causes populations to spatially segregate, which represses plasmid transfer. In contrast, resource cross-feeding causes populations to spatially intermix, which promotes plasmid transfer. We further show that the spatial positionings that emerge from metabolic interactions determine the proliferation of plasmid recipients. Our results demonstrate that metabolic interactions are important regulators of both the transfer and proliferation of plasmid-encoded antibiotic resistance.

Commercial Silver-Based Dressings: In Vitro and Clinical Studies in Treatment of Chronic and Burn Wounds

Chronic wounds are a major health problem because of delayed healing, causing hardships for the patient. The infection present in these wounds plays a role in delayed wound healing. Silver wound dressings have been used for decades, beginning in the 1960s with silver sulfadiazine for infection prevention for burn wounds. Since that time, there has been a large number of commercial silver dressings that have obtained FDA clearance. In this review, we examine the literature involving in vitro and in vivo (both animal and human clinical) studies with commercial silver dressings and attempt to glean the important characteristics of these dressings in treating infected wounds. The primary presentation of the literature is in the form of detailed tables. The narrative part of the review focuses on the different types of silver dressings, including the supporting matrix, the release characteristics of the silver into the surroundings, and their toxicity. Though there are many clinical studies of chronic and burn wounds using silver dressings that we discuss, it is difficult to compare the performances of the dressings directly because of the differences in the study protocols. We conclude that silver dressings can assist in wound healing, although it is difficult to provide general treatment guidelines. From a wound dressing point of view, future studies will need to focus on new delivery systems for silver, as well as the type of matrix in which the silver is deposited. Clearly, adding other actives to enhance the antimicrobial activity, including the disruption of mature biofilms is of interest. From a clinical point of view, the focus needs to be on the wound healing characteristics, and thus randomized control trials will provide more confidence in the results. The application of different wound dressings for specific wounds needs to be clarified, along with the application protocols. It is most likely that no single silver-based dressing can be used for all wounds.

L-Rhamnose Globally Changes the Transcriptome of Planktonic and Biofilm Escherichia coli Cells and Modulates Biofilm Growth

L-rhamnose, a naturally abundant sugar, plays diverse biological roles in bacteria, influencing biofilm formation and pathogenesis. This study investigates the global impact of L-rhamnose on the transcriptome and biofilm formation of PHL628 E. coli under various experimental conditions. We compared growth in planktonic and biofilm states in rich (LB) and minimal (M9) media at 28 °C and 37 °C, with varying concentrations of L-rhamnose or D-glucose as a control. Our results reveal that L-rhamnose significantly affects growth kinetics and biofilm formation, particularly reducing biofilm growth in rich media at 37 °C. Transcriptomic analysis through RNA-seq showed that L-rhamnose modulates gene expression differently depending on the temperature and media conditions, promoting a planktonic state by upregulating genes involved in rhamnose transport and metabolism and downregulating genes related to adhesion and biofilm formation. These findings highlight the nuanced role of L-rhamnose in bacterial adaptation and survival, providing insight into potential applications in controlling biofilm-associated infections and industrial biofilm management.

Intestinal biofilms: pathophysiological relevance, host defense, and therapeutic opportunities

SUMMARYThe human intestinal tract harbors a profound variety of microorganisms that live in symbiosis with the host and each other. It is a complex and highly dynamic environment whose homeostasis directly relates to human health. Dysbiosis of the gut microbiota and polymicrobial biofilms have been associated with gastrointestinal diseases, including irritable bowel syndrome, inflammatory bowel diseases, and colorectal cancers. This review covers the molecular composition and organization of intestinal biofilms, mechanistic aspects of biofilm signaling networks for bacterial communication and behavior, and synergistic effects in polymicrobial biofilms. It further describes the clinical relevance and diseases associated with gut biofilms, the role of biofilms in antimicrobial resistance, and the intestinal host defense system and therapeutic strategies counteracting biofilms. Taken together, this review summarizes the latest knowledge and research on intestinal biofilms and their role in gut disorders and provides directions toward the development of biofilm-specific treatments.

Development of "Intelligent particles" for the treatment of dental caries

Dental caries is one of the most prevalent non-communicable diseases worldwide, mediated by a multispecies biofilm that consists of high levels of acidogenic bacteria which ferment sugar to acid and cause teeth demineralization. Current treatment practice remains insufficient in addressing 1) rapid clearance of therapeutic agents from the oral environment 2) destroying bacteria that contribute to the healthy oral microbiome. In addition, increasing concerns over antibiotic resistance calls for innovative alternatives. In this study, we developed a pH responsive nano-carrier for delivery of polycationic silver nanoparticles. Branched-PEI capped silver nanoparticles (BPEI-AgNPs) were encapsulated in a tannic acid - Fe (III) complex-modified poly(D,L-lactic-co-glycolic acid) (PLGA) particle (Fe(III)-TA/PLGA@BPEI-AgNPs) to enhance binding to the plaque biofilm and demonstrate "intelligence" by releasing BPEI-AgNPs under acidic conditions that promote dental caries The constructed Fe(III)-TA/PLGA@BPEI-AgNPs (intelligent particles - IPs) exhibited significant binding to an axenic S. mutans biofilm grown on hydroxyapatite. Ag+ ions were released faster from the IPs at pH 4.0 (cariogenic pH) compared to pH 7.4. The antibiofilm results indicated that IPs can significantly reduce S. mutans biofilm volume and viability under acidic conditions. Cytotoxicity on differentiated Caco-2 cells and human gingival fibroblasts indicated that IPs were not cytotoxic. These findings demonstrate great potential of IPs in the treatment of dental caries.

The Guardian of Vision: Intelligent Bacteriophage-Based Eyedrops for Clinical Multidrug-Resistant Ocular Surface Infections

Clinical multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is the leading cause of refractory bacterial keratitis (BK). However, the reported BK treatment methods lack biosecurity and bioavailability, which usually causes irreversible visual impairment and even blindness. Herein, for BK caused by clinically isolated MDR-PA infection, armed phages are modularized with the type I photosensitizer (PS) ACR-DMT, and an intelligent phage eyedrop is developed for combined phagotherapy and photodynamic therapy (PDT). These eyedrops maximize the advantages of bacteriophages and ACR-DMT, enabling more robust and specific targeting killing of MDR-PA under low oxygen-dependence, penetrating and disrupting biofilms, and efficiently preventing biofilm reformation. Altering the biofilm and immune microenvironments alleviates inflammation noninvasively, promotes corneal healing without scar formation, protects ocular tissues, restores visual function, and prevents long-term discomfort and pain. This strategy exhibits strong scalability, enables at-home treatment of ocular surface infections with great patient compliance and a favorable prognosis, and has significant potential for clinical application.

Evolution and distribution of antibiotic resistance genes in submerged macrophytes and biofilm systems: From seasonal monitoring to mesocosm experiments

The aquatic ecosystem has been extensively investigated as a hotspot for the spread of antibiotic resistance genes (ARGs); yet, the evolution and distribution of ARGs profiles in submerged macrophytes biofilms and surrounding water remained unclear. In this study, the dynamic distribution and seasonal variations of microbial communities and ARGs profiles were investigated, alongside their assembly processes and mutual interactions. Bacitracin and multidrug resistance genes were predominant, constituting more than 60% of the total ARGs abundance. The deterministic processes (<65%), influenced by the physicochemical properties of the river environment, governed the assembly and composition of ARGs profiles, exhibiting significant seasonal variation. The peak diversity (21 types) and abundance (0.316 copy ratios) of ARGs were detected during the summer. Proteobacteria and Actinobacteria were the dominant bacterial phyla, accounting for 38.41-85.50% and 4.03-27.09% of the microbial community, respectively. Furthermore, Proteobacteria, especially genera such as Acinetobacter, Burkholderia, and Pseudomonas, with various resistance sequences, were the primary carriers of multiple ARGs. Notably, the genetic exchanges between biofilms and surrounding water facilitated the further propagation of high-risk ARGs, posing greater ecological risks. Redundancy analysis indicated that the total nitrogen and temperature in water determined the fate of pathogenic-resistant species. These findings provided theoretical support for the mitigation of ARGs contamination in aquatic environments.

Multi-omics analysis reveals genes and metabolites involved in Streptococcus suis biofilm formation

BACKGROUND

Streptococcus suis is an important zoonotic pathogen. Biofilm formation largely explains the difficulty in preventing and controlling S. suis. However, little is known about the molecular mechanism of S. suis biofilm formation.

RESULTS

In this study, transcriptomic and metabolomic analyses of S. suis in biofilm and planktonic states were performed to identify key genes and metabolites involved in biofilm formation. A total of 789 differential genes and 365 differential metabolites were identified. By integrating transcriptomics and metabolomics, five main metabolic pathways were identified, including amino acid pathway, nucleotide metabolism pathway, carbon metabolism pathway, vitamin and cofactor metabolism pathway, and aminoacyl-tRNA biosynthesis metabolic pathway.

CONCLUSIONS

These results provide new insights for exploring the molecular mechanism of S. suis biofilm formation.

In vitro elution of amikacin, cefazolin, gentamicin, ampicillin/sulbactam, and meropenem from a commercially available calcium sulfate delivery kit

Introduction

The use of implantable antibiotic beads has become a frequent treatment modality for the management of surgical site infections in human and veterinary medicine. The objective of this study is to describe the elution kinetics of five antibiotics from a commercially available calcium sulfate antibiotic delivery kit. A secondary goal was to compare elution concentrations with minimal inhibitory concentrations (MIC) for commonly encountered bacteria from the University of Florida's veterinary microbiology laboratory database.

Methods

Calcium sulfate powder was combined with amikacin, cefazolin, gentamicin, ampicillin/sulbactam, and meropenem. Triplicates of three antibiotic-loaded beads were immersed in 5 mL of phosphate-buffered saline (PBS) and kept at 37°C under constant agitation. Antibiotic-conditioned PBS was sampled at 14 time points from 1-h to 30 days and analyzed by liquid chromatography to determine the antibiotic concentration.

Results

All beads eluted concentrations of antibiotics for the 30-day sampling period, except for ampicillin/sulbactam, with the most antibiotics being eluted within the first week. The concentration of antibiotics within the eluent within the first 3-9 days (3- and 5-mm beads, respectively) was greater than the MIC of common isolates. The 5 mm bead samples were superior in maintaining higher concentrations for a longer period, compared to the 3-mm beads.

Discussion

CSH beads eluted antibiotics over the 30-day course of the study. Most of the antibiotic elution occurred within the first week and was maintained above the MIC of commonly encountered isolates. This information may be useful for clinical decision making for treatment of local infections encountered in practice.

Antimicrobial and Antibiofilm Activity of Monolaurin against Methicillin-Resistant Staphylococcus aureus Isolated from Wound Infections

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the major pathogens associated with life-threatening infections, showing resistance to various antibiotics. This study aimed to assess the influence of monolaurin on biofilm-forming MRSA.

Methods

The agar dilution method determined the minimum inhibitory concentration (MIC) of monolaurin against MRSA isolates and explored its impact on the resistance profile of selected antibiotics. The assessment of combined therapy involving monolaurin and antibiotics was conducted using fractional inhibitory concentration (FIC). The tissue culture plate strategy appraised monolaurin's antibiofilm activity and its inhibitory concentration (IC50), with assessment via scanning electron microscopy. Reverse transcription polymerase chain reaction (RT-PCR) discerned a monolaurin effect on the expression of the icaD gene.

Results

Monolaurin exhibited MIC values ranging from 500 to 2000 μg/mL. FIC index showed a synergistic effect of monolaurin with β-lactam antibiotics ranging from 0.0039 to 0.25 (p < 0.001). Among the 103 investigated MRSA isolates, 44 (44.7%) displayed moderate biofilm formation, while 59 (55.3%) were strong biofilm producers. Antibiofilm activity demonstrated concentration dependence, confirming monolaurin's capacity to inhibit biofilm formation and exhibited strong eradicating effects against preformed MRSA biofilms with IC50 values of 203.6 μg/mL and 379.3 μg/mL, respectively. Scanning electron microscope analysis revealed reduced cell attachments and diminished biofilm formation compared to the control. The expression levels of the icaD gene were remarkably reduced at monolaurin concentrations of 250 and 500 μg/mL.

Conclusion

Monolaurin had significant inhibitory effects on MRSA pre-existing biofilms as well as biofilm development. So, it can be employed in the treatment of severe infections, particularly those associated with biofilm formation including catheter-associated infections.

A 14-amino acid cationic peptide Bolespleenin334-347 from the marine fish mudskipper Boleophthalmus pectinirostris exhibiting potent antimicrobial activity and therapeutic potential

Antimicrobial peptides (AMPs) are an important component of innate immunity in both vertebrates and invertebrates, and some of the unique characteristics of AMPs are usually associated with their living environment. The marine fish, mudskipper Boleophthalmus pectinirostris, usually live amphibiously in intertidal environments that are quite different from other fish species, which would be an exceptional source of new AMPs. In the study, an AMP named Bolespleenin334-347 was identified, which was a truncated peptide derived from a new functional gene found in B. pectinirostris, that was up-regulated in response to bacterial challenge. Bolespleenin334-347 had only 14 amino acid residues, including five consecutive arginine residues. It was found that the peptide had broad-spectrum antibacterial activity, good thermal stability and sodium ion tolerance. Bolespleenin334-347 killed Acinetobacter baumannii and Staphylococcus aureus by disrupting the structural integrity of the bacterial membrane, leading to leakage of the cellular contents, and inducing accumulation of bacterial endogenous reactive oxygen species (ROS). In addition, Bolespleenin334-347 effectively inhibited biofilm formation of A. baumannii and S. aureus and long-term treatment did not lead to the development of resistance. Importantly, Bolespleenin334-347 maintained stable activity against clinically multi-drug resistant bacterial strains. In addition, it was noteworthy that Bolespleenin334-347 showed superior efficacy to LL-37 and vancomycin in a constructed mouse model of MRSA-induced superficial skin infections, as evidenced by a significant reduction in bacterial load and more favorable wound healing. This study provides an effective antimicrobial agent for topical skin infections with potential therapeutic efficacy for infections with drug-resistant bacteria, including MRSA.

Community context influences the conjugation efficiency of Escherichia coli

In urinary tract infections (UTIs), different bacteria can live in a polymicrobial community consisting of different species. It is unknown how community members affect the conjugation efficiency of uropathogenic Escherichia coli. We investigated the influence of individual species often coisolated from urinary infections (UTI) on the conjugation efficiency of E. coli isolates in artificial urine medium. Pairwise conjugation rate experiments were conducted between a donor E. coli strain containing the pOXA-48 plasmid and six uropathogenic E. coli isolates, in the presence and absence of five different species commonly coisolated in polymicrobial UTIs to elucidate their effect on the conjugation efficiency of E. coli. We found that the basal conjugation rates of pOXA-48, in the absence of other species, are dependent on the bacterial host genetic background. Additionally, we found that bacterial interactions have an overall positive effect on the conjugation rate of pOXA-48. Particularly, Gram-positive enterococcal species were found to enhance the conjugation rates towards uropathogenic E. coli isolates. We hypothesize that the nature of the coculture and physical interactions are important for these increased conjugation rates in an artificial urine medium environment.

High-throughput combination assay for studying biofilm formation of uropathogenic Escherichia coli

Uropathogenic Escherichia coli, the most common cause for urinary tract infections, forms biofilm enhancing its antibiotic resistance. To assess the effects of compounds on biofilm formation of uropathogenic Escherichia coli UMN026 strain, a high-throughput combination assay using resazurin followed by crystal violet staining was optimized for 384-well microplate. Optimized assay parameters included, for example, resazurin and crystal violet concentrations, and incubation time for readouts. For the assay validation, quality parameters Z' factor, coefficient of variation, signal-to-noise, and signal-to-background were calculated. Microplate uniformity, signal variability, edge well effects, and fold shift were also assessed. Finally, a screening with known antibacterial compounds was conducted to evaluate the assay performance. The best conditions found were achieved by using 12 µg/mL resazurin for 150 min and 0.023% crystal violet. This assay was able to detect compounds displaying antibiofilm activity against UMN026 strain at sub-inhibitory concentrations, in terms of metabolic activity and/or biomass.

Nanomaterial in controlling biofilms and virulence of microbial pathogens

The escalating threat of antimicrobial resistance (AMR) poses a grave concern to global public health, exacerbated by the alarming shortage of effective antibiotics in the pipeline. Biofilms, intricate populations of bacteria encased in self-produced matrices, pose a significant challenge to treatment, as they enhance resistance to antibiotics and contribute to the persistence of organisms. Amid these challenges, nanotechnology emerges as a promising domain in the fight against biofilms. Nanomaterials, with their unique properties at the nanoscale, offer innovative antibacterial modalities not present in traditional defensive mechanisms. This comprehensive review focuses on the potential of nanotechnology in combating biofilms, focusing on green-synthesized nanoparticles and their associated anti-biofilm potential. The review encompasses various aspects of nanoparticle-mediated biofilm inhibition, including mechanisms of action. The diverse mechanisms of action of green-synthesized nanoparticles offer valuable insights into their potential applications in addressing AMR and improving treatment outcomes, highlighting novel strategies in the ongoing battle against infectious diseases.

A Single Base Change in the csgD Promoter Resulted in Enhanced Biofilm in Swine-Derived Salmonella Typhimurium

Pathogenic Salmonella strains causing gastroenteritis typically can colonize and proliferate in the intestines of multiple host species. They retain the ability to form red dry and rough (rdar) biofilms, as seen in Salmonella enterica serovar Typhimurium. Conversely, Salmonella serovar like Typhi, which can cause systemic infections and exhibit host restriction, are rdar-negative. In this study, duck-derived strains and swine-derived strains of S. Typhimurium locate on independent phylogenetic clades and display relative genomic specificity. The duck isolates appear more closely related to human blood isolates and invasive non-typhoidal Salmonella (iNTS), whereas the swine isolates were more distinct. Phenotypically, compared to duck isolates, swine isolates exhibited enhanced biofilm formation that was unaffected by the temperature. The transcriptomic analysis revealed the upregulation of csgDEFG transcription as the direct cause. This upregulation may be mainly attributed to the enhanced promoter activity caused by the G-to-T substitution at position -44 of the csgD promoter. Swine isolates have created biofilm polymorphisms by altering a conserved base present in Salmonella Typhi, iNTS, and most Salmonella Typhimurium (such as duck isolates). This provides a genomic characteristics perspective for understanding Salmonella transmission cycles and evolution.

Perioperative interventions for the prevention of surgical wound infection in adult patients undergoing left ventricular assist devices implantation: A scoping review

BACKGROUND

Surgical wound infection is the most frequent type of care health associated infection. Lack of knowledge about the prevention of surgical wound infection in patients undergoing left ventricular assist device implantation could significantly undermine the potential benefits of surgical intervention.

OBJECTIVES

This study aimed to map the recommendations for adult patients undergoing left ventricular assist device implantation.

DESIGN

This is a scoping review, being registered in the Open Science Framework under DOI https://doi.org/10.17605/OSF.IO/Q76B3 (https://osf.io/q76b3/).

METHOD

Left ventricular assist device coordinators and nurse specialists in dermatology and stomatherapy conducted a scoping review in Scopus, The Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature (CINAHL), limited to the period between 2015 and 2022. The results of this scoping review will be discussed and presented in separate articles. This paper will synthesize research evidence on the perioperative topic.

RESULTS

The initial searches resulted in 771 studies. Sixty nine met the eligibility criteria and were included in the scoping review. Eight articles addressing the perioperative topic that answered the question of this article were included.

CONCLUSION

Although this scoping review included heterogeneous, and scarce studies with left ventricular assist device patients. As such, there are many promising future research directions for this topic.

IMPLICATIONS FOR CLINICAL PRACTICE

Infection surveillance should be an integral part of left ventricular assist device implantation programs in health care institutions. Velvet completely buried in subcutaneous tissues reduces transmission system infection. Triple tunnel method reduces transmission system infection risk.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Assessing antibacterial efficacy of a polyhexanide hydrogel versus alginate-based wound dressing in burns

OBJECTIVE

Burn injuries pose a heightened risk of infection, which is primarily responsible for increased morbidity and mortality. Factors such as extensive skin damage and compromised immunity exacerbate this vulnerability. Pseudomonas aeruginosa and Staphylococcus aureus are frequently identified in burns, with Gram-negative Pseudomonas aeruginosa often resistant to antibacterial agents. While Flaminal, an alginate-based wound dressing (Flen Health, Belgium), aids wound healing, its antibacterial effects are limited compared with 1% silver sulfadiazine (1% SSD). In contrast, Prontosan Wound Gel X, a betaine and polyhexanide-based hydrogel (B. Braun Medical AG, Switzerland), has been shown to effectively combat various microbes and promotes wound healing.

METHOD

In this study, two research cohorts were retrospectively established (control group: patients receiving standard of care with the alginate-based wound dressing; intervention group: patients receiving the polyhexanide hydrogel wound dressing), comprising patients admitted to a burn centre between 2019 and 2022. Patients were eligible when continuous wound treatment with either of the two wound dressings was performed. Laser Doppler imaging (LDI) scans were conducted. Regions of interest (ROIs) were selected based on LDI scans and divided into healing time categories. Wound swabs were collected and the presence of Pseudomonas aeruginosa and Staphylococcus aureus was documented. Bacterial load was evaluated using a semiquantitative scale. Wound healing was recorded.

RESULTS

The control group consisted of 31 patients with 93 ROIs, while the intervention group had 67 ROIs involving 29 patients. Both groups exhibited similar proportions of healing time categories (p>0.05). The polyhexanide hydrogel dressing outperformed the alginate-based dressing in antiseptic efficacy by significantly reducing the incidence of Pseudomonas aeruginosa- and Staphylococcus aureus-positive cultures in patients' wounds. Wound healing time for conservative treatment was comparable between groups.

CONCLUSION

In this study, the polyhexanide hydrogel dressing minimised Pseudomonas aeruginosa and Staphylococcus aureus colonisation in burn wounds, demonstrating strong antibacterial properties, emphasising its potential to minimise infections in burn injuries.

Antibiotic Resistance, Biofilm Formation, and Persistent Phenotype of Klebsiella pneumoniae in a Vietnamese Tertiary Hospital: A Focus on Amikacin

Klebsiella pneumoniae stands out as a major opportunistic pathogen responsible for both hospital- and community-acquired bacterial infections. This study comprehensively assesses the antibiotic resistance, amikacin persistent patterns, and biofilm-forming ability of 247 isolates of K. pneumoniae obtained from an intensive care unit of a tertiary hospital in Vietnam. Microdilution assays, conducted on a 96-well plate, determined the minimum inhibitory concentrations (MICs) of amikacin. Susceptibility data for other antibiotics were gathered from the antibiogram profile. Stationary-phase bacteria were exposed to 50 × MIC, and viable bacteria counts were measured to determine amikacin persistence. Biofilm forming capacity on 96-well polystyrene surfaces was assessed by biomass and viable bacteria. The prevalence of resistance was notably high across most antibiotics, with 64.8% classified as carbapenem-resistant K. pneumoniae and 81.4% as multidrug resistant. Amikacin, however, exhibited a relatively low rate of resistance. Of the isolates, 58.2% demonstrated a moderate to strong biofilm formation capacity, and these were found to be poorly responsive to amikacin. K. pneumoniae reveals a significant inclination for amikacin persistence, with ∼45% of isolates displaying an antibiotic antibiotic-survival ratio exceeding 10%. The study sheds light on challenges in treating of K. pneumoniae infection in Vietnam, encompassing a high prevalence of antibiotic resistance, a substantial ability to form biofilm, and a notable rate of antibiotic persistence.

The Role of Metallurgical Features in the Microbially Influenced Corrosion of Carbon Steel: A Critical Review

Microbially influenced corrosion (MIC) is a potentially critical degradation mechanism for a wide range of materials exposed to environments that contain relevant microorganisms. The likelihood and rate of MIC are affected by microbiological, chemical, and metallurgical factors; hence, the understanding of the mechanisms involved, verification of the presence of MIC, and the development of mitigation methods require a multidisciplinary approach. Much of the recent focus in MIC research has been on the microbiological and chemical aspects, with less attention given to metallurgical attributes. Here, we address this knowledge gap by providing a critical synthesis of the literature on the metallurgical aspects of MIC of carbon steel, a material frequently associated with MIC failures and widely used in construction and infrastructure globally. The article begins by introducing the process of MIC, then progresses to explore the complexities of various metallurgical factors relevant to MIC in carbon steel. These factors include chemical composition, grain size, grain boundaries, microstructural phases, inclusions, and welds, highlighting their potential influence on MIC processes. This review systematically presents key discoveries, trends, and the limitations of prior research, offering some novel insights into the impact of metallurgical factors on MIC, particularly for the benefit of those already familiar with other aspects of MIC. The article concludes with recommendations for documenting metallurgical data in MIC research. An appreciation of relevant metallurgical attributes is essential for a critical assessment of a material's vulnerability to MIC to advance research practices and to broaden the collective knowledge in this rapidly evolving area of study.

The use of combination therapy for the improvement of colistin activity against bacterial biofilm

Colistin is used as a last resort for the management of infections caused by multi-drug resistant (MDR) bacteria. However, the use of this antibiotic could lead to different side effects, such as nephrotoxicity, in most patients, and the high prevalence of colistin-resistant strains restricts the use of colistin in the clinical setting. Additionally, colistin could induce resistance through the increased formation of biofilm; biofilm-embedded cells are highly resistant to antibiotics, and as with other antibiotics, colistin is impaired by bacteria in the biofilm community. In this regard, the researchers used combination therapy for the enhancement of colistin activity against bacterial biofilm, especially MDR bacteria. Different antibacterial agents, such as antimicrobial peptides, bacteriophages, natural compounds, antibiotics from different families, N-acetylcysteine, and quorum-sensing inhibitors, showed promising results when combined with colistin. Additionally, the use of different drug platforms could also boost the efficacy of this antibiotic against biofilm. The mentioned colistin-based combination therapy not only could suppress the formation of biofilm but also could destroy the established biofilm. These kinds of treatments also avoided the emergence of colistin-resistant subpopulations, reduced the required dosage of colistin for inhibition of biofilm, and finally enhanced the dosage of this antibiotic at the site of infection. However, the exact interaction of colistin with other antibacterial agents has not been elucidated yet; therefore, further studies are required to identify the precise mechanism underlying the efficient removal of biofilms by colistin-based combination therapy.

Effect of N-acetyl cysteine, rifampicin, and ozone on biofilm formation in pan-resistant Klebsiella pneumoniae: an experimental study

BACKGROUND

To the best of our knowledge, this is the first study to evaluate the effectiveness of specific concentrations of antibiofilm agents, such as N-acetyl cysteine (NAC), rifampicin, and ozone, for the treatment of pan-resistant Klebsiella pneumoniae (PRKp).

OBJECTIVES

We evaluated the effectiveness of antibiofilm agents, such as NAC, rifampicin, and ozone, on biofilm formation in PRKp at 2, 6, 24, and 72 h.

DESIGN AND SETTING

This single-center experimental study was conducted on June 15, 2017, and July 15, 2018, at Istanbul Faculty of Medicine, Istanbul University, Turkey.

METHODS

Biofilm formation and the efficacy of these agents on the biofilm layer were demonstrated using colony counting and laser-screened confocal microscopy.

RESULTS

NAC at a final concentration of 2 μg/mL was administered to bacteria that formed biofilms (24 h), and no significant decrease was detected in the bacterial counts of all isolates (all P > 0.05). Rifampicin with a final concentration of 0.1 μg/mL was administered to bacteria that formed biofilm (24 h), and no significant decrease was detected in bacterial count (all P > 0.05). Notably, ozonated water of even 4.78 mg/L concentration for 72 h decreased the bacterial count by ≥ 2 log10.

CONCLUSION

Different approaches are needed for treating PRKp isolates. We demonstrate that PRKp isolates can be successfully treated with higher concentrations of ozone.

Use of Hydrogen Peroxide Vapour for Microbiological Disinfection in Hospital Environments: A Review

Disinfection of nosocomial pathogens in hospitals is crucial to combat healthcare-acquired infections, which can be acquired by patients, visitors and healthcare workers. However, the presence of a wide range of pathogens and biofilms, combined with the indiscriminate use of antibiotics, presents infection control teams in healthcare facilities with ongoing challenges in the selection of biocides and application methods. This necessitates the development of biocides and innovative disinfection methods that overcome the shortcomings of conventional methods. This comprehensive review finds the use of hydrogen peroxide vapour to be a superior alternative to conventional methods. Motivated by observations in previous studies, herein, we provide a comprehensive overview on the utilisation of hydrogen peroxide vapour as a superior high-level disinfection alternative in hospital settings. This review finds hydrogen peroxide vapour to be very close to an ideal disinfectant due to its proven efficacy against a wide range of microorganisms, safety to use, lack of toxicity concerns and good material compatibility. The superiority of hydrogen peroxide vapour was recently demonstrated in the case of decontamination of N95/FFP2 masks for reuse to address the critical shortage caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the COVID-19 pandemic. Despite the significant number of studies demonstrating antimicrobial activity, there remains a need to critically understand the mechanism of action by performing studies that simultaneously measure damage to all bacterial cell components and assess the correlation of this damage with a reduction in viable cell count. This can lead to improvement in antimicrobial efficacy and foster the development of superior approaches.

Phase variation modulates the multi-phenotypes displayed by clinical Campylobacter jejuni strains

The high incidence and prevalence of Campylobacter spp. in the food supply chain entail the importance to understand their mechanisms developed to withstand harsh environmental conditions encountered. Different stress conditions and phenotypic approaches were evaluated to study the behaviour of five clinical C. jejuni isolates with different genotypes, including the tolerance to oxygen and the oxidants hydrogen peroxide and cumene hydroperoxide, the motility and the ability to form biofilm on polystyrene and stainless steel at different temperatures and atmospheres. Whole Genome Sequencing was performed to analyse the occurrence of 216 genes involved in these mechanisms plus phase variation. The isolates showed high tolerance to oxygen and peroxide stress with different swimming motility performances and biofilm formation abilities. Aerotolerance was related with a reduced sensitive to peroxide stress and a loss of motility that promotes biofilm formation depending on the material surface. Comparative genomics did not reveal any clear gene pattern, although phase variation occurring during host infection was observed to be crucial for the modulation of the different survival mechanisms adopted by the bacteria. These findings reveal that the bacteria can combine diverse and complex strategies in an efficient manner to survive and persist in the environment.

Analysis of Spatial and Biochemical Characteristics of In Vitro Cariogenic Biofilms

Background Dental caries is the most common bacterial disease of calcified tissues of teeth. Cariogenic biofilms formed on the tooth surface secrete organic acids and thus result in demineralization. Delving into the depth of biofilms is crucial to understand the pathogenic mechanisms and design improved therapeutic approaches. The aim of the study is to analyze the spatial and biochemical characteristics of cariogenic biofilms. Materials and methods Pulp tissue samples sourced from freshly extracted third molars were incubated with oral cariogenic bacteria namely Streptococcus mutans, Staphylococcus aureus, Escherichia coli, Entamoeba faecalis, and Candida albicans to form the biofilm. Spatial assessment of biofilms was done under FESEM (field emission scanning electron microscope, JSM-IT800, JEOL, Tokyo, Japan). FTIR (Fourier transform infrared spectroscopy, Alpha II, Bruker, Germany) spectra were assessed for chemical molecular interactions in 24- and 48-hour time periods.  Results Morphological assessment with FESEM revealed rapid growth and aggregation within a short time period. FTIR spectra to analyze chemical constituents of biofilm presented with varied peaks of water, amide A, amide I, water, lipids, and phospholipids. Conclusion Further validation with more advanced imaging for an extended time period is vital to derive better conclusive evidence.

Progress of stimulus responsive nanosystems for targeting treatment of bacterial infectious diseases

In recent decades, due to insufficient concentration at the lesion site, low bioavailability and increasingly serious resistance, antibiotics have become less and less dominant in the treatment of bacterial infectious diseases. It promotes the development of efficient drug delivery systems, and is expected to achieve high absorption, targeted drug release and satisfactory therapy effects. A variety of endogenous stimulation-responsive nanosystems have been constructed by using special infection microenvironments (pH, enzymes, temperature, etc.). In this review, we firstly provide an extensive review of the current research progress in antibiotic treatment dilemmas and drug delivery systems. Then, the mechanism of microenvironment characteristics of bacterial infected lesions was elucidated to provide a strong theoretical basis for bacteria-targeting nanosystems design. In particular, the discussion focuses on the design principles of single-stimulus and dual-stimulus responsive nanosystems, as well as the use of endogenous stimulus-responsive nanosystems to deliver antimicrobial agents to target locations for combating bacterial infectious diseases. Finally, the challenges and prospects of endogenous stimulus-responsive nanosystems were summarized.

A protocol for an overview of systematic reviews to map photodynamic inactivation evidence in different dental specialties

This is a protocol for an overview to summarize the findings of Systematic Reviews (SR) dealing with Photodynamic Inactivation (PDI) for control of oral diseases. Specific variables of oral infectious will be considered as outcomes, according to dental specialty. Cochrane Database of Systematic Reviews (CDSR), MEDLINE, LILACS, Embase, and Epistemonikos will be searched, as well as reference lists. A search strategy was developed for each database using only terms related to the intervention (PDI) aiming to maximize sensitivity. After checking for duplicate entries, selection of reviews will be performed in a two-stage technique: two authors will independently screening titles and abstracts, and then full texts will be assessed for inclusion/exclusion criteria. Any disagreement will be resolved through discussion and/or consultation with a third reviewer. Data will be extracted following the recommendations in Chapter V of Cochrane Handbook and using an electronic pre-specified form. The evaluation of the methodological quality and risk of bias (RoB) of the SR included will be carried out using the AMSTAR 2 and ROBIS. Narrative summaries of relevant results from the individual SR will be carried out and displayed in tables and figures. A specific summary will focus on PDI parameters and study designs, such as the type and concentration of photosensitizer, pre-irradiation time, irradiation dosimetry, and infection or microbiological models, to identify the PDI protocols with clinical potential. We will summarize the quantitative results of the SRs narratively.

Constitutive Activation of RpoH and the Addition of L-arabinose Influence Antibiotic Sensitivity of PHL628 E. coli

Antibiotics are used to combat the ever-present threat of infectious diseases, but bacteria are continually evolving an assortment of defenses that enable their survival against even the most potent treatments. While the demand for novel antibiotic agents is high, the discovery of a new agent is exceedingly rare. We chose to focus on understanding how different signal transduction pathways in the gram-negative bacterium Escherichia coli (E. coli) influence the sensitivity of the organism to antibiotics from three different classes: tetracycline, chloramphenicol, and levofloxacin. Using the PHL628 strain of E. coli, we exogenously overexpressed two transcription factors, FliA and RpoH.I54N (a constitutively active mutant), to determine their influence on the minimum inhibitory concentration (MIC) and minimum duration of killing (MDK) concentration for each of the studied antibiotics. We hypothesized that activating these pathways, which upregulate genes that respond to specific stressors, could mitigate bacterial response to antibiotic treatment. We also compared the exogenous overexpression of the constitutively active RpoH mutant to thermal heat shock that has feedback loops maintained. While FliA overexpression had no impact on MIC or antibiotic tolerance, RpoH.I54N overexpression reduced the MIC for tetracycline and chloramphenicol but had no independent impact on antibiotic tolerance. Thermal heat shock alone also did not affect MIC or antibiotic tolerance. L-arabinose, the small molecule used to induce expression in our system, unexpectedly independently increased the MICs for tetracycline (>2-fold) and levofloxacin (3-fold). Additionally, the combination of thermal heat shock and arabinose provided a synergistic, 5-fold increase in MIC for chloramphenicol. Arabinose increased the tolerance, as assessed by MDK99, for chloramphenicol (2-fold) and levofloxacin (4-fold). These experiments highlight the potential of the RpoH pathway to modulate antibiotic sensitivity and the emerging implication of arabinose in enhanced MIC and antibiotic tolerance.

Microfluidics for adaptation of microorganisms to stress: design and application

Microfluidic systems have fundamentally transformed the realm of adaptive laboratory evolution (ALE) for microorganisms by offering unparalleled control over environmental conditions, thereby optimizing mutant generation and desired trait selection. This review summarizes the substantial influence of microfluidic technologies and their design paradigms on microbial adaptation, with a primary focus on leveraging spatial stressor concentration gradients to enhance microbial growth in challenging environments. Specifically, microfluidic platforms tailored for scaled-down ALE processes not only enable highly autonomous and precise setups but also incorporate novel functionalities. These capabilities encompass fostering the growth of biofilms alongside planktonic cells, refining selection gradient profiles, and simulating adaptation dynamics akin to natural habitats. The integration of these aspects enables shaping phenotypes under pressure, presenting an unprecedented avenue for developing robust, stress-resistant strains, a feat not easily attainable using conventional ALE setups. The versatility of these microfluidic systems is not limited to fundamental research but also offers promising applications in various areas of stress resistance. As microfluidic technologies continue to evolve and merge with cutting-edge methodologies, they possess the potential not only to redefine the landscape of microbial adaptation studies but also to expedite advancements in various biotechnological areas. KEY POINTS: • Microfluidics enable precise microbial adaptation in controlled gradients. • Microfluidic ALE offers insights into stress resistance and distinguishes between resistance and persistence. • Integration of adaptation-influencing factors in microfluidic setups facilitates efficient generation of stress-resistant strains.