Biofilm Persistence Research Articles

STUDY OF PREVALENCE OF MULTI-DRUG RESISTANT ACINETOBACTER SPECIES IN VENTILATOR-ASSOCIATED PNEUMONIAE CASES IN A TERTIARY CARE HOSPITAL, VISAKHAPATNAM

Objective: Acinetobacter sps are important oppurtunistic pathogens with their significance in colonising and persistent biofilm production capabilities. The aim of the present study was to assess the prevalence of multidrug-resistant Acinetobacter sps in ventilator-associated pneumoniae cases in a tertiary care hospital Visakhapatnam. Methods: A prospective study was conducted on 328 endotracheal aspirate samples received in Clinical Laboratory, Department of Microbiology for a period of 1 y, from June 2023 to June 2024, in mechanical ventilated cases, admitted in intensive care units, in a tertiary care hospital, Visakhapatnam. Results: Out of 328 samples received, 42 (12.8%) were Acinetobacter isolates with resistance to Aminoglycosides (66.7%), Cephalosporins (57.1%), Quinolones (52.4%), Carbapenems (42.9%). Biofilm production was identified in 31 isolates (73.8%) by Congo Red Agar method in this study. Conclusion: The potential ability of Acinetobacter sps to form biofilms and antibiotic selective pressure leading to emergence of resistant clones is directly proportional to the injudicious use of antibiotics. There is a strict need of antibiotic stewardship measures in intensive care units to restrict development of pan-resistant strains.

Magnetic Hercules Swarm for Precise and Effective Deep Biofilm Eradication

AbstractOver the past decade, significant advancements in micro‐nano robots have enabled non‐invasive operations in hazardous, confined environments, particularly targeting persistent bacterial biofilms in hard‐to‐reach areas. However, many of these robots are limited by poor magnetic properties, hindering their effectiveness against biofilms. This study proposes a novel strategy using a swarm with strong magnetic effects (Hercules swarm) combined with near‐infrared (NIR) light for effective biofilm eradication. Carbonyl iron particles coated with polydopamine (CI@PDA), averaging ≈3 µm in diameter, demonstrate clustering and significant magneto‐force under a rotating magnetic field due to their large magnetic saturation. This enables the Hercules swarm to achieve rapid delivery (100 mm s−1), efficient cargo transport (carrying twice its own weight), and effective catheter clearance (1 mm min−1). The controllable motion and high photothermal activity enable precise biofilm eradication without toxic agents. The aggregation of magnetic particles into chains and their rotation are explored by improved particle dynamic model. Simulations also reveal enhanced fluid convection and mechanical pressure around the particle chain. Due to its easy operation, straightforward controllability, and environmental compatibility, the magnetic Hercules swarm emerges as a promising treatment modality for eliminating biofilms entrenched within intricate, narrow, and convoluted medical implants or industrial conduits.

Race for the surface between THP-1 macrophages and Staphylococcus aureus on various titanium implants with well-defined topography and wettability.

Gristina et al. (1987) suggested the fate of a biomaterial is decided in a “race for the surface” between pathogens and the host. To gain deeper insight into the mechanisms behind this concept, we investigated the “race for the surface” across three co-culture scenarios with THP-1 macrophages and Staphylococcus aureus (1:1 ratio), varying the order of addition: (i) simultaneous, (ii) macrophages first, and (iii) S. aureus first, on six Ti6Al4V-ELI surfaces modified with specific topographies and wettability. The outcome of the race for the surface was not influenced by these biomaterials but by the chronological introduction of macrophages and S. aureus. When macrophages and S. aureus arrived simultaneously, macrophages won the race, leading to the lowest number of viable S. aureus through rapid phagocytosis and killing. When macrophages arrived and established first, macrophages still prevailed but under greater challenge resulting from the lower bacterial killing efficiency of adherent macrophages and numerous viable intracellular bacteria, supporting the concept of the so-called immunocompromised zone around implants (upregulation of TLR-2 receptor and pro-inflammatory IL-1β). When S. aureus arrived first establishing a biofilm, bacteria won the race, leading to macrophage dysfunction and cell death (upregulation of FcγR and TLR-2 receptors, NF-κB signaling, NOX2 mediated reactive oxygen species), contributing to a persistent biofilm phenotype (upregulation of clfA, icaA, sarA, downregulation of agrA, hld, lukAB) and intracellular survival of S. aureus (lipA upregulation). The clinical implications are bacterial colonization of the implant and persistence of intracellular bacteria in periprosthetic tissues, which can lead to infection chronicity. Statement of SignificanceGristina et al. (1987) suggested the fate of a biomaterial is decided in a “race for the surface” between bacterial pathogens and host cells. There is a lack of in vitro co-culture models and knowledge on macrophage-S. aureus interactions on biomaterial surfaces, and none has evaluated the expression of virulence factors in S. aureus biofilms.We have successfully developed co-culture models and molecular panels and elucidated important cellular and molecular interactions between macrophages and S. aureus on a broad range of titanium biomaterials with well-defined surface topography and wettability. Our findings highlight the critical role of biofilm formation and the chronological order of bacteria or macrophage arrival in determining the fate of the surface.

E. coli cells advance into phase-separated (biofilm-simulating) extracellular polymeric substance containing DNA, HU, and lipopolysaccharide.

Understanding the constitution and behavior of biofilms is crucial to understanding how to deal with persistent biofilms. This study, together with other recent studies from our group, elucidates a novel aspect of the extracellular polymeric substance (EPS) of Escherichia coli biofilms, by creating a simulacrum of the EPS and then demonstrating that its formation involves liquid-liquid phase separation (LLPS) of HU, DNA, and lipopolysaccharide (LPS) components, with LPS determining the liquidity of this EPS simulacrum. The findings provide insight into the nature of biofilms and into how the interplay of HU, DNA, and LPS could modulate the structural integrity and functional dynamics of biofilms.

Cyclic di-GMP as an antitoxin regulates bacterial genome stability and antibiotic persistence in biofilms

Cyclic di-GMP as an antitoxin regulates bacterial genome stability and antibiotic persistence in biofilms

Cyclic di-GMP as an antitoxin regulates bacterial genome stability and antibiotic persistence in biofilms.

Biofilms are complex bacterial communities characterized by a high persister prevalence, which contributes to chronic and relapsing infections. Historically, persister formation in biofilms has been linked to constraints imposed by their dense structures. However, we observed an elevated persister frequency accompanying the stage of cell adhesion, marking the onset of biofilm development. Subsequent mechanistic studies uncovered a comparable type of toxin-antitoxin (TA) module (TA-like system) triggered by cell adhesion, which is responsible for this elevation. In this module, the toxin HipH acts as a genotoxic deoxyribonuclease, inducing DNA double strand breaks and genome instability. While the second messenger c-di-GMP functions as the antitoxin, exerting control over HipH expression and activity. The dynamic interplay between c-di-GMP and HipH levels emerges as a crucial determinant governing genome stability and persister generation within biofilms. These findings unveil a unique TA system, where small molecules act as the antitoxin, outlining a biofilm-specific molecular mechanism influencing genome stability and antibiotic persistence, with potential implications for treating biofilm infections.

Clinical efficacy and safety of a silver ion-releasing foam dressing on hard-to-heal wounds: a meta-analysis.

Delayed or stalled healing in open wounds can result from persisting chronic inflammation related to infection and/or persistent bacterial colonisation and biofilm. Treatment of hard-to-heal wounds focuses on debridement and exudate management, but also on infection prevention and control. Silver dressings have been evaluated in randomised clinical trials (RCTs); this meta-analysis evaluated the efficacy and safety of a silver ion-releasing foam dressing (Biatain Ag; Coloplast A/S, Denmark) to treat hard-to-heal wounds. Literature databases (PubMed and Cochrane Library) were searched for studies on silver ion-releasing foam dressings in the treatment of hard-to-heal wounds. Individual patient data from four RCTs were obtained and included in the meta-analysis. Findings showed that treatment with the silver ion-releasing foam dressing was associated with a significantly higher relative reduction in wound area after four (least squares-mean difference (LS-MD): -12.55%, 95% confidence interval (CI): (-15.95, -9.16); p<0.01) and six weeks of treatment (LS-MD: -11.94%, 95%CI: (-17.21, -6.68); p<0.01) compared with controls. Significant benefits were also observed for time to disappearance of odour (hazard ratio: 1.61, 95%CI: (1.31, 1.98); p<0.01), relative reduction of exudate (LS-MD: -5.15, 95%CI: (-7.36, -2.94); p<0.01), proportion of patients with periwound erythema (relative risk (RR): 0.81, 95%CI: (0.69; 0.94); p<0.01), and less pain at dressing removal (LS-MD: -0.35, 95%CI: (-0.63, -0.06); p=0.02). No differences regarding safety outcomes were identified. This meta-analysis has demonstrated beneficial outcomes and a good tolerability profile for silver ion-releasing foam dressings in the treatment of moderate-to-highly exuding wounds with delayed healing compared with control dressings.

Reuterin Enhances the Efficacy of Peracetic Acid Against Multi-species Dairy Biofilm.

Biofilms may contain pathogenic and spoilage bacteria and can become a recurring problem in the dairy sector, with a negative impact on product quality and consumer health. Peracetic acid (PAA) is one of the disinfectants most frequently used to control biofilm formation and persistence. Though effective, it cannot be used at high concentrations due to its corrosive effect on certain materials and because of toxicity concerns. The aim of this study was to test the possibility of PAA remaining bactericidal at lower concentrations by using it in conjunction with reuterin (3-hydroxypropionaldehyde). We evaluated the efficacy of PAA in pure form or as BioDestroy®, a PAA-based commercial disinfectant, on three-species biofilms formed by dairy-derived bacteria, namely Pseudomonas azotoformans PFlA1, Serratia liquefaciens Sl-LJJ01, and Bacillus licheniformis Bl-LJJ01. Minimum inhibitory concentrations of the three agents were determined for each bacterial species and the fractional inhibitory concentrations were then calculated using the checkerboard assay. The minimal biofilm eradication concentration (MBEC) of each antibacterial combination was then calculated against mixed-species biofilm. PAA, BioDestroy®, and reuterin showed antibiofilm activity against all bacteria within the mixed biofilm at respectively 760ppm, 450ppm, and 95.6mM. The MBEC was lowered significantly to 456ppm, 337.5ppm, and 71.7mM, when exposed to reuterin for 16h followed by contact with disinfectant. Combining reuterin with chemical disinfection shows promise in controlling biofilm on food contact surfaces, especially for harsh or extended treatments. Furthermore, systems with reuterin encapsulation and nanotechnologies could be developed for sustainable antimicrobial efficacy without manufacturing disruptions.

Diversification of Pseudomonas aeruginosa Biofilm Populations under Repeated Phage Exposures Decreases the Efficacy of the Treatment.

Phage therapy has been proposed as a therapeutic alternative to antibiotics for the treatment of chronic, biofilm-related P. aeruginosa infections. To gain a deeper insight into the complex biofilm-phage interactions, we investigated in the present study the effect of three successive exposures to lytic phages of biofilms formed by the reference strains PAO1 and PA14 as well as of two sequential clinical P. aeruginosa isolates from the sputum of a patient with cystic fibrosis (CF). The Calgary device was employed as a biofilm model and the efficacy of phage treatment was evaluated by measurements of the biomass stained with crystal violet (CV) and of the cell density of the biofilm bacterial population (CFU/mL) after each of the three phage exposures. The genetic alterations of P. aeruginosa isolates from biofilms exposed to phages were investigated by whole-genome sequencing. We show here that the anti-biofilm efficacy of the phage treatment decreased rapidly with repeated applications of lytic phages on P. aeruginosa strains with different genetic backgrounds. Although we observed the maintenance of a small subpopulation of sensitive cells after repeated phage treatments, a fast recruitment of mechanisms involved in the persistence of biofilms to the phage attack occurred, mainly by mutations causing alterations of the phage receptors. However, mutations causing phage-tolerant phenotypes such as alginate-hyperproducing mutants were also observed. In conclusion, a decreased anti-biofilm effect occurred after repeated exposure to lytic phages of P. aeruginosa biofilms due to the recruitment of different resistance and tolerance mechanisms.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities.

Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation. In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria. Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

Whole-genome sequencing establishes persistence of biofilm-associated Pseudomonas aeruginosa detected from microbiological surveillance of gastrointestinal endoscopes

BackgroundAn increased incidence of P. aeruginosa in microbiological surveillance (MS) cultures from gastrointestinal endoscopes was detected between March 2020 to March 2023 in Tan Tock Seng Hospital Singapore. The aim of this report is to describe the use of whole-genome sequencing (WGS) in this investigation. MethodsWGS was performed for all P. aeruginosa isolates with pairwise comparison of isolates to assess for genomic linkage. Comprehensive review of reprocessing practices and environmental sampling was performed. FindingsTwenty-two P. aeruginosa isolates were detected from endoscopic MS cultures. Fifteen (68%) isolates were available for WGS. Eighteen pairwise comparisons of isolates were made, of which 10 were found to be genomically linked. One endoscope had P. aeruginosa repeatedly cultured from subsequent MS that were genomically linked and persistent despite repeat endoscopic reprocessing, establishing the persistence of biofilm that could not be eradicated with routine reprocessing. All P. aeruginosa isolates cultured from other different endoscopes were genetically distinct.Investigation into reprocessing practices revealed the use of air/water valves connected to endoscopes during clinical use. Inspection of these valves revealed the presences of cracks and tears. All other environmental samples were negative. ConclusionsThe WGS findings helped to deprioritize common source contamination and supported the hypothesis of biofilm buildup within endoscopes leading to repeatedly positive MS cultures that were genomically linked. This was possibly related to incomplete reprocessing of the damaged air/water valves, resulting in biofilm build up. All faulty valves were changed and subsequently cleaned separately with ultrasonic cleaning followed by sterilization which resolved this incident.

An NIR-propelled janus nanomotor with enhanced ROS-scavenging, immunomodulating and biofilm-eradicating capacity for periodontitis treatment

Periodontitis is an inflammatory disease caused by bacterial biofilms, which leads to the destruction of periodontal tissue. Current treatments, such as mechanical cleaning and antibiotics, struggle to effectively address the persistent biofilms, inflammation, and tissue damage. A new approach involves developing a Janus nanomotor (J-CeM@Au) by coating cerium dioxide-doped mesoporous silica (CeM) with gold nanoparticles (AuNPs). This nanomotor exhibits thermophoretic motion when exposed to near-infrared (NIR) laser light due to the temperature gradient produced by the photothermal effects of asymmetrically distributed AuNPs. The NIR laser provides the energy for propulsion and activates the nanomotor's antibacterial properties, allowing it to penetrate biofilms and kill bacteria. Additionally, the nanomotor's ability to scavenge reactive oxygen species (ROS) can modulate the immune response and create a regenerative environment, promoting the healing of periodontal tissue. Overall, this multifunctional nanomotor offers a promising new approach for treating periodontitis by simultaneously addressing biofilm management and immune modulation with autonomous movement.

Current scenario of indole hybrids with antibacterial potential against Acinetobacter baumannii pathogens: A mini-review.

Acinetobacter baumannii with the capability to "escape" almost all currently available antibacterials is eroding the safety of basic medical interventions and is an increasing cause of mortality globally, prompting a substantial requirement for new classes of antibacterial agents. Indoles participate in the regulation of persistent bacterial formation, biofilm formation, plasmid stability, and drug resistance. In particular, indole hybrids demonstrated promising antibacterial activity against both drug-sensitive and drug-resistant A. baumannii pathogens, representing a fertile source for the discovery of novel therapeutic agents for clinical deployment in controlling A. baumannii infections. This mini-review outlines the current innovations of indole hybrids with antibacterial activity against A. baumannii pathogens, covering articles published from 2020 to the present, to open new avenues for exploring novel anti-A. baumannii candidates.

Development of Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Pseudomonas aeruginosa multi-species in vitro dry surface biofilm models: Insights into resilience and persistence in low-moisture environments

Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Pseudomonas aeruginosa can persist as dry surface biofilms (DSB) and survive desiccation for prolonged periods of time. This could serve as potential sources of contamination in low-moisture food (LMF) processing environments. The objectives of this study were to develop in vitro mono-and mix-culture DSB models to better understand pathogen survival under dehydrated conditions as DSB. Mono-and mix-culture wet surface biofilms (WSB) of S. enterica ser. Typhimurium ATCC 14028, L. monocytogenes FSL R8-5318, and P. aeruginosa ATCC 15442 were developed following EPA MLB SOP MB-19 protocol on borosilicate glass coupons using a CDC® biofilm reactor. WSB were harvested and dried for 24, 48, and 72 h at 21 °C to form DSB. Mean log10 CFU/cm2 were calculated at each desiccation time point and compared to control (WSB) using LSM of PROC GLM to fit linear models (P = 0.05). Approximately 8.8 ± 1.7, 7.1 ± 1.1, 6.9 ± 0.6, and 6.3 ± 0.8 mean log10 CFU/coupon were recovered from mono-culture Salmonella DSB at 0, 24, 48, and 72 h, respectively. Overall, Salmonella mean log10 densities were limited when co-cultured with P. aeruginosa although there were no significant differences in Salmonella density over desiccation time points. Mean log10 CFU/coupon for L. monocytogenes monoculture DSB were comparatively lower i.e., 5.7 ± 0.4 (0 h), 3.8 ± 0.1 (24 h), and 3.4 ± 0.6 (48 h), and 2.6 ± 0.3 (72 h). However, when co-cultured with P. aeruginosa, L. monocytogenes exhibited consistently higher cell densities 6.7 ± 0.4, 6.0 ± 0.9, 5.6 ± 0.04, and 4.9 ± 0.6, at 0, 24, 48, and 72 h, respectively. On average, P. aeruginosa consistently exceeded six log10 at each desiccation time point in co-culture. Confocal laser scanning microscopy (CLSM) images confirmed biofilm development and persistence over time in mono and mixed cultures. This work provides foundational evidence toward better understanding pathogen survival under dehydrated conditions, interactions between different pathogens within desiccated biofilms, and their respective survival rates. Additionally, these data provide quantitative assessment of bacterial load within DSB under high-risk scenarios for LMFs. These models provide opportunities to explore targeted mitigation strategies, including efficacy of dry sanitation practices, to prevent the formation or remove DSB in LMF processing environments.

Protective Activity and Safety of Experimental Acellular Pertussis Vaccines Based on Antigenic Complexes Isolated from Biofilm and Planktonic Cultures of Bordetella pertussis.

Continued circulation of the whooping cough pathogen, even in countries with high vaccine coverage, can be related to persistence of Bordetella pertussis biofilms in the respiratory tract. The films differ from planktonic cells by increased resistance to the host immune system and antibacterial drugs. The available acellular pertussis vaccines (aPV) containing antigens isolated from planktonic cultures of B. pertussis protect from severe forms of whooping cough, but do not effectively influence circulation of virulent strains in the subclinical forms of the disease and asymptomatic carriage. It is promising to create new generation aPV based on antigens isolated from biofilm cultures of B. pertussis capable of more effectively controlling the entire infectious cycle of whooping cough, including colonization, persistence, and transmission of the pathogen. From antigenic complexes isolated from the culture medium of biofilm and planktonic cultures of the strain B. pertussis No. 317 (serotype 1.2.3), experimental aPV were made: aPV-B and aPV-P, respectively. In intracerebral infection of mice with a virulent strain of B. pertussis, aPV-B demonstrated 2.5-fold higher protective activity than aPV-P and also more effectively reduced colonization of the lungs by B. pertussis cells in mice after intranasal infection with a virulent strain. Both vaccine preparations were safe and did not cause death in mice after administration of histamine.

Regulation of candidalysin underlies Candida albicans persistence in intravascular catheters by modulating NETosis.

Candida albicans is a leading cause of intravascular catheter-related infections. The capacity for biofilm formation has been proposed to contribute to the persistence of this fungal pathogen on catheter surfaces. While efforts have been devoted to identifying microbial factors that modulate C. albicans biofilm formation in vitro, our understanding of the host factors that may shape C. albicans persistence in intravascular catheters is lacking. Here, we used multiphoton microscopy to characterize biofilms in intravascular catheters removed from candidiasis patients. We demonstrated that, NETosis, a type of neutrophil cell death with antimicrobial activity, was implicated in the interaction of immune cells with C. albicans in the catheters. The catheter isolates exhibited reduced filamentation and candidalysin gene expression, specifically in the total parenteral nutrition culture environment. Furthermore, we showed that the ablation of candidalysin expression in C. albicans reduced NETosis and conferred resistance to neutrophil-mediated fungal biofilm elimination. Our findings illustrate the role of neutrophil NETosis in modulating C. albicans biofilm persistence in an intravascular catheter, highlighting that C. albicans can benefit from reduced virulence expression to promote its persistence in an intravascular catheter.

Green approaches for biofilm eradication: Enhancing cleaning efficiency

AbstractCleaning up biocontamination from surfaces is a critical aspect of maintaining a hygienic environment. Traditional cleaning methods often fall short when it comes to eliminating persistent biofilms and resilient bacteria. In recent years, alternative approaches utilizing antibiofilm enzymes, bacteriophages, essential oils (EOs), antibacterial peptides, and biosurfactants have emerged as promising strategies to combat biocontamination. This article explores the efficiency of these agents in targeting and eradicating biofilms, highlighting their mechanisms of action and potential applications. By leveraging the unique properties of these materials, we can enhance cleaning practices and improve public health outcomes by effectively eliminating biocontamination from various surfaces.

Bactericidal and biofilm eradication efficacy of a fluorinated benzimidazole derivative, TFBZ, against methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major inducement of nosocomial infections and its biofilm formation render the high tolerance to conventional antibiotics, which highlights the requirement to develop new antimicrobial agents urgently. In this study, we identified a fluorinated benzimidazole derivative, TFBZ, with potent antibacterial efficacy toward planktonic MRSA (MIC = 4μg/mL, MBC = 8μg/mL) and its persistent biofilms (≥99%, MBEC = 8μg/mL). TFBZ manifested significant irreversible time-dependent killing against MRSA as characterized by diminished cell viability, bacterial morphological change and protein leakage. Furthermore, the results from CBD devices, crystal violet assay in conjunction with live/dead staining and scanning electron microscopy confirmed that TFBZ was capable of eradicating preformed MRSA biofilms with high efficiency. Simultaneously, TFBZ reduced the bacterial invasiveness and exerted negligible hemolysis and cytotoxicity toward mammalian cells, which ensuring the robust therapeutic effect on mouse skin abscess model. The transcriptome profiling and quantitative RT-PCR revealed that a set of encoding genes associated with cell adhesion, biofilm formation, translation process, cell wall biosynthesis was consistently downregulated in MRSA biofilms upon exposure to TFBZ. In conclusion, TFBZ holds promise as a valuable candidate for therapeutic applications against MRSA chronic infections.

Granulocytic myeloid-derived suppressor cell activity during biofilm infection is regulated by a glycolysis/HIF1a axis.

Staphylococcus aureus is a leading cause of biofilm-associated prosthetic joint infection (PJI). A primary contributor to infection chronicity is an expansion of granulocytic myeloid-derived suppressor cells (G-MDSCs), which are critical for orchestrating the antiinflammatory biofilm milieu. Single-cell sequencing and bioinformatic metabolic algorithms were used to explore the link between G-MDSC metabolism and S. aureus PJI outcome. Glycolysis and the hypoxia response through HIF1a were significantly enriched in G-MDSCs. Interfering with both pathways in vivo, using a 2-deoxyglucose nanopreparation and granulocyte-targeted Hif1a conditional KO mice, respectively, attenuated G-MDSC-mediated immunosuppression and reduced bacterial burden in a mouse model of S. aureus PJI. In addition, single-cell RNA-Seq (scRNA-Seq) analysis of granulocytes from PJI patients also showed an enrichment in glycolysis and hypoxia-response genes. These findings support the importance of a glycolysis/HIF1a axis in promoting G-MDSC antiinflammatory activity and biofilm persistence during PJI.

Surface topography and chemistry of food contact substances, and microbial nutrition affect pathogen persistence and symbiosis in cocktail Listeria monocytogenes biofilms

The foodborne pathogen Listeria monocytogenes (L. monocytogenes) can form very persistent biofilms on food contact substances, either in monospecies, or in conjunction with background microflora. Although some studies have investigated how bacterial symbiosis facilitates L. monocytogenes survival in complex cocktail biofilms, very little is known about how this core symbiotic relationship is affected by environmental factors. Here, we investigate how L. monocytogenes persistence is affected by symbiosis with Escherichia coli O157:H7, Pseudomonas fluorescens, and Ralstonia insidiosa, and how these relationships are impacted by environmental factors, including food contact surface topography and chemistry, and microbial nutrition. We find that symbiosis can significantly enhance L. monocytogenes persistence in four-species cocktail biofilms (5.71 ± 0.03 Log CFU/cm2) by up to 1.9 Log CFU/cm2 compared to monospecies biofilms (3.81 ± 0.08 Log CFU/cm2). We also report that surface topography and chemistry, microbial nutrition, and symbiont species significantly impact the symbiotic relationships involving L. monocytogenes, revealing the adaptability of bacterial symbiosis to changing environmental conditions and the complex nature of cocktail pathogen biofilms. Antagonistic and synergistic interactions involving pathogens in cocktail biofilms, and factors affecting those interactions, are elucidated and can establish a foundation to study symbiosis and its role in mitigating pathogen persistence in food systems, and helping identify unanticipated increased food safety risks of pathogens due to enhanced persistence.