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Inactivation of <i>Pseudomonas aeruginosa</i> Biofilms by 405-Nanometer-Light-Emitting Diode Illumination
摘要： Biofilm formation by Pseudomonas aeruginosa contributes to its survival on surfaces and represents a major clinical threat because of the increased tolerance of biofilms to disinfecting agents. This study aimed to investigate the efficacy of 405-nm light-emitting diode (LED) illumination in eliminating P. aeruginosa biofilms formed on stainless steel coupons under different temperatures. Time-dependent killing assays using planktonic and biofilm cells were used to determine the antimicrobial and antibiofilm activity of LED illumination. We also evaluated the effects of LED illumination on the disinfectant susceptibility, biofilm structure, extracellular polymeric substance (EPS) structure and composition, and biofilm-related gene expression of P. aeruginosa biofilm cells. Results showed that the abundance of planktonic P. aeruginosa cells was reduced by 0.88, 0.53, and 0.85 log CFU/mL following LED treatment for 2 h compared with untreated controls at 4, 10, and 25°C, respectively. For cells in biofilms, significant reductions (1.73, 1.59, and 1.68 log CFU/cm2) were observed following LED illumination for 2 h at 4, 10, and 25°C, respectively. Moreover, illuminated P. aeruginosa biofilm cells were more sensitive to benzalkonium chloride or chlorhexidine compared with untreated cells. Scanning electron microscopy and confocal laser scanning microscopic observation indicated that both the biofilm structure and EPS structure were disrupted by LED illumination. Further, reverse transcription-quantitative PCR revealed that LED illumination downregulated the transcription of several genes associated with biofilm formation. These findings suggest that LED illumination has the potential to be developed as an alternative method for prevention and control of P. aeruginosa biofilm contamination.
关键词： light-emitting diode,disinfectant,extracellular polymeric substances,biofilm-related genes,Pseudomonas aeruginosa,biofilm
更新于2025-09-23 15:19:57
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Blue laser light inhibits biofilm formation in vitro and in vivo by inducing oxidative stress
摘要： Resolution of bacterial infections is often hampered by both resistance to conventional antibiotic therapy and hiding of bacterial cells inside biofilms, warranting the development of innovative therapeutic strategies. Here, we report the efficacy of blue laser light in eradicating Pseudomonas aeruginosa cells, grown in planktonic state, agar plates and mature biofilms, both in vitro and in vivo, with minimal toxicity to mammalian cells and tissues. Results obtained using knock-out mutants point to oxidative stress as a relevant mechanism by which blue laser light exerts its anti-microbial effect. Finally, the therapeutic potential is confirmed in a mouse model of skin wound infection. Collectively, these data set blue laser phototherapy as an innovative approach to inhibit bacterial growth and biofilm formation, and thus as a realistic treatment option for superinfected wounds.
关键词： oxidative stress,Pseudomonas aeruginosa,blue laser light,antimicrobial effect,biofilm formation
更新于2025-09-19 17:13:59
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Highly selective and sensitive online measurement of trace exhaled HCN by acetone-assisted negative photoionization time-of-flight mass spectrometry with in-source CID
摘要： Exhaled hydrogen cyanide (HCN) has been extensively investigated as a promising biomarker of the presence of Pseudomonas aeruginosa in the airways of patients with cystic fibrosis (CF) disease. Its concentration profile for exhalation can provide useful information for medical disease diagnosis and therapeutic procedures. However, the complexity of breath gas, like high humidity, carbon dioxide (CO2) and trace organic compounds, usually leads to quantitative error, poor selectivity and sensitivity for HCN with some of existing analytical techniques. In this work, acetone-assisted negative photoionization (AANP) based on a vacuum ultraviolet (VUV) lamp with a time-of-flight mass spectrometer (AANP-TOFMS) was firstly proposed for online measurement of trace HCN in human breath. In-source collision-induced dissociation (CID) was adopted for sensitivity improvement and the signal response of the characteristic ion CN? (m/z 26) was improved by about 24-fold. For accurate and reliable analysis of the exhaled HCN, matrix influences in the human breath including humidity and CO2 were investigated, respectively. A Nafion tube was used for online dehumidification of breath samples. Matrix-adapted calibration in the concentration range of 0.5–50 ppbv with satisfactory dynamic linearity and repeatability was obtained. The limit of quantitation (LOQ) for HCN at 0.5 ppbv was achieved in the presence of 100% relative humidity and 4% CO2. Finally, the method was successfully applied for online determination of human mouth- and nose-exhaled HCN, and the nose-exhaled HCN were proved to be reliable for assessing systemic HCN levels for individuals. The results are encouraging and highlight the potential of AANP-TOFMS with in-source CID as a selective, accurate, sensitive and noninvasive technique for determination of the exhaled HCN for CF clinical diagnosis and HCN poisoning assessment.
关键词： Cystic fibrosis,Acetone-assisted negative photoionization,Hydrogen cyanide,Time-of-flight mass spectrometry,Pseudomonas aeruginosa,In-source collision-induced dissociation
更新于2025-09-19 17:13:59
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Femtosecond Laser-Assisted Penetrating Keratoplasty for Treating Infective Keratitis
摘要： To report the results of penetrating keratoplasty (PKP) assisted by femtosecond laser in the treatment of persistent infective keratitis. Seven eyes of 7 patients with diagnosed infective keratitis were recruited. They showed no improvement on maximal medical therapy for a week. The causative organisms were Pseudomonas aeruginosa in 3 cases and Fusarium in 4 cases. All cases underwent femtosecond laser-assisted PKP with a mushroom-shaped cut. Post-operative antimicrobial medications were continued for 8–12 weeks. Sutures were removed after 6 months. Therapeutic success was de?ned as eradication of primary infection. Functional success was considered when visual function improves to 20/200 or better. All 7 eyes underwent femtosecond laser-assisted PKP. There were no intraoperative complications, and all patients had uneventful recipient cornea separation. Anatomic, therapeutic, and functional success was achieved in all patients. During the 6-month follow-up period, no recurrence of infection was reported. The average preoperative corrected distance visual acuity (CDVA) was 2.07 log of the minimal angle of resolution (LogMAR) 6 0.21, whereas at 6 months postoperatively, the average CDVA was 0.17 LogMAR 6 0.13, with a P value of 0.00025. Femtosecond laser-assisted PKP was found to be an effective method for treating infective keratitis (particularly that caused by Pseudomonas aeruginosa and Fusarium) that did not respond to medical treatment. Early surgical intervention before the disease becomes advanced is recommended.
关键词： therapeutic penetrating keratoplasty TPK,penetrating keratoplasty,resistant keratitis,femto-keratoplasty,femtosecond laser,antifungal therapy,Pseudomonas aeruginosa,infective keratitis,Fusarium
更新于2025-09-12 10:27:22
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Morphologies controlled ZnO for inactivation of multidrug resistant pseudomonas aeruginosa in solar light
摘要： The different morphology and size of the zinc oxide (ZnO) were synthesized by a co-precipitation process via variation of calcination temperature from 400 oC to 900 oC. The nanorod, flower, hexagon, pentagon, and microflambeau morphologies were obtained. Flower morphology of ZnO tends to inactivate multidrug resistant Pseudomonas aeruginosa (P. aeruginosa) completely within 45 min under solar light irradiation than other morphologies due to efficient separation electron-hole pairs. The P. aeruginosa inactivation was confirmed by transmission electron microscope (TEM) images, DNA fragmentation (gel electrophoresis) and protein degradation (Bradford assay). The TEM mapping illustrates the damaging of bacteria by active species but not the releasing of Zn2+ ions in bacteria cell. The prevention of charge recombination was confirmed by transient photocurrent response and electrochemical impedance spectra (EIS) measurements. Electron spin resonance (ESR) spectroscopy suggests that O2ˉ?, OH?, and h+ are responsible for P. aeruginosa inactivation in solar light. So, this work provides a detail investigation of morphology/size dependent photocatalytic inactivation of multidrug resistant pathogen in solar light.
关键词： ZnO,Solar light,Flower,bacterial inactivation,Pseudomonas aeruginosa
更新于2025-09-12 10:27:22
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Antimicrobial Biophotonic Treatment of Ampicillin-Resistant Pseudomonas aeruginosa with Hypericin and Ampicillin Cotreatment Followed by Orange Light
摘要： Bacterial antibiotic resistance is an alarming global issue that requires alternative antimicrobial methods to which there is no resistance. Antimicrobial photodynamic therapy (APDT) is a well-known method to combat this problem for many pathogens, especially Gram-positive bacteria and fungi. Hypericin and orange light APDT efficiently kill Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and the yeast Candida albicans. Although Gram-positive bacteria and many fungi are readily killed with APDT, Gram-negative bacteria are difficult to kill due to their different cell wall structures. Pseudomonas aeruginosa is one of the most important opportunistic, life-threatening Gram-negative pathogens. However, it cannot be killed successfully by hypericin and orange light APDT. P. aeruginosa is ampicillin resistant, but we hypothesized that ampicillin could still damage the cell wall, which can promote photosensitizer uptake into Gram-negative cells. Using hypericin and ampicillin cotreatment followed by orange light, a significant reduction (3.4 log) in P. aeruginosa PAO1 was achieved. P. aeruginosa PAO1 inactivation and gut permeability improvement by APDT were successfully shown in a Caenorhabditis elegans model.
关键词： hypericin,antimicrobial photodynamic therapy (APDT),Pseudomonas aeruginosa,ampicillin,Caenorhabditis elegans,orange light
更新于2025-09-11 14:15:04
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Hydrogen Peroxide Enhances the Antibacterial Effect of Methylene Blue-based Photodynamic Therapy on Biofilm-forming Bacteria
摘要： Recently, increased attention has been focused on endoscopic disinfection after outbreaks of drug resistant infections associated with gastrointestinal endoscopy. The aims of this study were to investigate the bactericidal efficacy of methylene blue (MB)-based photodynamic therapy (PDT) on Pseudomonas aeruginosa (P. aeruginosa), which is the major cause of drug resistant post-endoscopy outbreak, and to assess the synergistic effects of hydrogen peroxide addition to MB-based PDT on biofilms. In planktonic state of P. aeruginosa, the maximum decrease was 3 log10 and 5.5 log10 at 20 and 30 J / cm2, respectively, following MB-based PDT. However, the maximum reduction of colony forming unit (CFU) was decreased by 2.5 log10 and 3 log10 irradiation on biofilms. The biofilm formation was significantly inhibited upon irradiation with MB-based PDT. When the biofilm state of P. aeruginosa was treated with MB-based PDT with hydrogen peroxide, the CFU was significantly decreased by 6 log10 after 20 J / cm2, by 7 log10 after 30 J / cm2 irradiation, suggesting significantly higher efficacy than MB-based PDT alone. The implementation of the combination of hydrogen peroxide with MB-based PDT through working channels might be appropriate for preventing early colonization and biofilm formation in the endoscope and post-endoscopy outbreak.
关键词： methylene blue,endoscopic disinfection,hydrogen peroxide,Pseudomonas aeruginosa,photodynamic therapy,biofilm
更新于2025-09-10 09:29:36
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UV light assisted antibiotics for eradication of in vitro biofilms
摘要： The overuse of antibiotics is accelerating the bacterial resistance, and therefore there is a need to reduce the amount of antibiotics used for treatment. Here, we demonstrate in vitro that specific wavelengths in a narrow range around 296 nm are able to eradicate bacteria in the biofilm state (grown for 24 hours) more effectively, than antibiotics and the combination of irradiation and antibiotics is even better, introducing a novel concept light assisted antibiotics. The investigated wavelength range was 249 nm to 338 nm with an approximate step of 5 nm. The novel concept that consists of a UV irradiation treatment followed by a tobramycin treatment can significantly reduce the amount of antibiotics needed for eradicating mature bacterial biofilms. The efficiency of the proposed light assisted antibiotics method was compared to combinatory antibiotic treatment and highly concentrated antibiotic monotherapy. The eradication efficacies, on mature biofilms, achieved by light assisted antibiotic and by the antibiotic monotherapy at approximately 10-fold higher concentration, were equivalent. The present achievement could motivate the development of light assisted antibiotic treatments for treating infections.
关键词： UV light,light assisted antibiotics,Pseudomonas aeruginosa,biofilm eradication,antibiotics
更新于2025-09-10 09:29:36
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Modeling of ultraviolet (UV) radiation under a large pilot-scale designed for wastewater disinfection and inactivation of selected bacteria of Pseudomonas aeruginosa in a laboratory UV device
摘要： The aim of this paper was to propose a modeling system of water ultraviolet (UV) disinfection. Results reveal that application of the model of Chick-Watson in its original form or modified are not representative of the kinetics of disinfection. For this reason, the application of a new kinetic model of Collins-Selleck in UV inactivation of Pseudomonas aeruginosa in secondary wastewater appeared to be the best applied model. The modeling of the reactivation process at range of 7.5-50°C temperature was shown. First-order saturation does not fit the obtained data in photoreactivation; a modification of the model is proposed coinciding with the classical logistic equation. To better explain the process of inactivation, we have assumed that the action of disinfectant on the survival of lonely microorganisms is faster than its action on suspended solids protected or agglomerated to each other. For this reason, the application of a new kinetic model by introducing a third factor reflecting the influence of suspended solids in water on disinfection kinetics appeared to be determinant for modeling UV inactivation of P. aeruginosa in secondary treated wastewater.
关键词： ultraviolet (UV) disinfection,photoreactivation,modeling,Pseudomonas aeruginosa,Secondary wastewater,suspended solids
更新于2025-09-09 09:28:46