Prolonged Exposure to Antimicrobials Induces Changes in Susceptibility to Antibiotics, Biofilm Formation and Pathogenicity in Staphylococcus aureus

Introduction: Frequent exposure to certain biocidal agents such as hypochlorous acid (HOCl), triclosan and benzalkonium chloride (BAC) has been reported to induce significant changes in Staphylococcus aureus. However, very few studies of this type have been conducted with conventional antimicrobials. Aim: The current investigation aimed to explore the phenotypic changes (susceptibility to antibiotics, biofilm formation and relative pathogenicity) that occur in S. aureus after recurrent exposure to antimicrobials. Methods: We compared the effects of long-term exposure to ampicillin, cefazoline, kanamycin and silver nanoparticles (AgNPs) on their susceptibility to antibiotics, biofilm formation, growth rate and pathogenicity in Staphylococcus aureus ATCC 6538. The minimum inhibitory concentrations (MIC) were determined using the microplate mircodilution method and the bacteria were exposed to increasing concentrations of each antimicrobial (MIC/2 to MIC) prepared in the BHIB for 8 days. The sensitivity of bacteria to antibiotics was assessed using the Kirby-Bauer disc diffusion method, the biofilm formation with crystal violet bacterial attachment assay and relative pathogenicity was assessed through a Galleria mellonella waxworm model. Results: The data in this investigation indicate that long-term exposure to antimicrobials may induce several changes in S. aureus. The exposure to ampicillin induced resistance to ceftazidime, tetracycline and ceftriaxone while the susceptibility to ceftazidime decreased in bacteria exposed to cefazolin and Kanamycin. Meanwhile, exposure to AgNPs induced some changes in susceptibility to trimethoprim and ceftazidime without causing resistance. Similarly, the strains exposed to ampicillin and kanamycin grew more rapidly and produced more biofilms than the control strains whereas the strains exposed to the AgNPs produced less biofilms. On G. melonella model, cefazolin seems to have attenuated the pathogenicity while the 3 other strains were more pathogenic than the controls. Conclusion: Long term exposure of S. aureus to antibiotics and AgNPs induces several changes in susceptibility to other antibiotics, growth rate, biofilm formation and pathogenicity; and these changes should be taken into account when choosing antibiotics for treatment of diseases caused by S. aureus.

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Evaluation of Changes Induced in the Probiotic Escherichia coli M17 Following Recurrent Exposure to Antimicrobials

Journal of Pharmaceutical Research International ◽

10.9734/jpri/2021/v33i29b31601 ◽

2021 ◽

pp. 158-167

Author(s):

M. J. A. Mbarga ◽

I. V. Podoprigora ◽

E. G. Volina ◽

A. V. Ermolaev ◽

L. A. Smolyakova

Keyword(s):

Escherichia Coli ◽

Growth Rate ◽

Silver Nanoparticles ◽

Biofilm Formation ◽

Fold Increase ◽

Bacterial Attachment ◽

Diffusion Method ◽

Cross Resistance ◽

Microdilution Method ◽

Similar Work

Introduction: It is already well known that the exposure of certain bacteria, pathogenic or not, to antimicrobials is likely to increase their virulence and induce the development of direct or cross resistance to antimicrobials, but there is almost no information available regarding probiotics. Aim: To assess the changes induced in susceptibility to antibiotics, biofilm formation, growth rate and relative pathogenicity in the probiotic Escherichia coli M17 (EC-M17) after long exposure to antimicrobials namely ampicillin, kanamycin, cefazolin and silver nanoparticles (AgNPs). Methods: After determining the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the 4 antimicrobials above-mentioned by the microdilution method, EC-M17 was exposed to increasing subinhibitory doses ranging from MIC/8 to MIC for 8 days. The susceptibility to antibiotics of the mutants obtained was assessed by the Kirby Bauer disc diffusion method, biofilm formation by the Congo red agar method and with crystal violet bacterial attachment assay, and relative pathogenicity was assessed using a Galleria melonella waxworm model. Results: Exposure to antimicrobials induces noticeable changes in EC-M17. The highest adaptation to antimicrobials was observed on AgNPs with 8-fold increase in MIC and 16-fold increase in MBC of AgNPs. EC-M17 exposed to ampicillin, kanamycin and silver nanoparticles became resistant to ampicillin, ceftazidime, ceftazidime/clavulanate and tetracycline while exposure to cefazolin induced a significant decrease in sensitivity to tetracycline and ampicillin and resistance to ceftazidime/clavulanate and ceftazidime. The strain exposed to ampicillin was the only one to produce more biofilm than the control strain and except the EC-M17 exposed to cefazolin, all other EC-M17 strains were more pathogenic on G. melonella model than the control. Conclusion: Data in this investigation suggest that repeated exposure of the probiotic EC-M17 to antimicrobials may induce changes in antimicrobials susceptibility, biofilm formation, growth rate, and relative pathogenicity. Therefore, as far as possible, the probiotic E. coli M17 should not be used in combination with antibiotics and further investigations are required to expand similar work on more probiotics in order to avoid resistance build-up which might be transmitted by horizontal transfer.

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Attenuated Virulence and Biofilm Formation in Staphylococcus aureus following Sublethal Exposure to Triclosan

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05904-11 ◽

2012 ◽

Vol 56 (6) ◽

pp. 3092-3100 ◽

Cited By ~ 47

Author(s):

Joe Latimer ◽

Sarah Forbes ◽

Andrew J. McBain

Keyword(s):

Staphylococcus Aureus ◽

Growth Rate ◽

Growth Rates ◽

Biofilm Formation ◽

Galleria Mellonella ◽

Concentration Gradients ◽

Content Type ◽

Small Colony Variant ◽

Small Colony ◽

Repeated Passage

ABSTRACTSubeffective exposure ofStaphylococcus aureusto the biocide triclosan can reportedly induce a small-colony variant (SCV) phenotype.S. aureusSCVs are characterized by low growth rates, reduced pigmentation, and lowered antimicrobial susceptibility. While they may exhibit enhanced intracellular survival, there are conflicting reports regarding their pathogenicity. The current study reports the characteristics of an SCV-like strain ofS. aureuscreated by repeated passage on sublethal triclosan concentrations.S. aureusATCC 6538 (the passage 0 [P0] strain) was serially exposed 10 times to concentration gradients of triclosan to generate strain P10. This strain was then further passaged 10 times on triclosan-free medium (designated strain ×10). The MICs and minimum bactericidal concentrations of triclosan for P0, P10, and ×10 were determined, and growth rates in biofilm and planktonic cultures were measured. Hemolysin, DNase, and coagulase activities were measured, and virulence was determined using aGalleria mellonellapathogenicity model. Strain P10 exhibited decreased susceptibility to triclosan and characteristics of an SCV phenotype, including a considerably reduced growth rate and the formation of pinpoint colonies. However, this strain also had delayed coagulase production, had impaired hemolysis (P< 0.01), was defective in biofilm formation and DNase activity, and displayed significantly attenuated virulence. Colony size, hemolysis, coagulase activity, and virulence were only partially restored in strain ×10, whereas the planktonic growth rate was fully restored. However, ×10 was at least as defective in biofilm formation and DNase production as P10. These data suggest that although repeated exposure to triclosan may result in an SCV-like phenotype, this is not necessarily associated with increased virulence and adapted bacteria may exhibit other functional deficiencies.

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Molecular Investigation of Fibronectin-Binding Protein Genes and Capacity of Biofilm Production in Staphylococcus Aureus Isolated From Clinical Samples

10.21203/rs.3.rs-640880/v1 ◽

2021 ◽

Author(s):

Hossein Jafari Soghondicolaei ◽

Mohammad Ahanjan ◽

Mehrdad Gholami ◽

Bahman Mirzaei ◽

Hamid Reza Goli

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Colorimetric Assay ◽

Binding Protein ◽

Clinical Isolates ◽

Diffusion Method ◽

Clinical Samples ◽

Biofilm Production ◽

Fibronectin Binding Protein ◽

Fibronectin Binding

Abstract Biofilm production increases Staphylococcus aureus resistance to antibiotics and also host defense mechanisms. The current study aims to evaluate the biofilm formation by S. aureus and to determine the prevalence of fibronectin-binding protein genes, also its correlation with drug resistance. In this study, 100 clinical isolates of S. aureus were collected. The antibiotic susceptibility pattern of the isolates was evaluated by the disk agar diffusion method. The ability of biofilm formation in the studied isolates was also determined by microplate colorimetric assay. Then, all isolates were screened by polymerase chain reaction for the fnbA and fnbB genes. Out of 100 clinical isolates of S. aureus, the highest and lowest antibiotic resistance rates were against penicillin (94%) and vancomycin (6%). Thirty-two cases were found to be multi-drug resistant (MDR) among the all strains. The ability of biofilm production was observed in 89% of the isolates. The PCR results showed that the prevalence of fnbA and fnbB genes were 91% and 17%, respectively. Moreover, 100% and 21.8% of the MDR strains harbored the fnbA and fnbB genes respectively. The ability to form biofilm in MDR isolates of S. aureus is more than non-MDR isolates, especially fnbA positive ones. As the bacteria in the biofilm are difficult to kill by antibiotics, attention to the removal or control of the biofilm production seems to be necessary.

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An Alanine-Rich Peptide Attenuates Quorum Sensing-Regulated Virulence and Biofilm Formation in Staphylococcus aureus

Journal of AOAC International ◽

10.5740/jaoacint.18-0251 ◽

2019 ◽

Vol 102 (4) ◽

pp. 1228-1234 ◽

Cited By ~ 1

Author(s):

Raid Al Akeel ◽

Ayesha Mateen ◽

Rabbani Syed

Keyword(s):

Gene Expression ◽

Staphylococcus Aureus ◽

Quorum Sensing ◽

Biofilm Formation ◽

Bacterial Attachment ◽

The Body ◽

Dependent Manner ◽

Virulence Determinants ◽

Microarray Gene Expression ◽

Concentration Dependent Manner

Abstract Background: Alanine-rich proteins/peptides (ARP), with bioactivity of up to 20 amino acid residues, can be observed by the body easily during gastrointestinal digestion. Objective: Populus trichocarpa extract’s capability to attenuate quorum sensing-regulated virulence and biofilm formation in Staphylococcus aureus is described. Methods: PT13, an ARP obtained from P. trichocarpa, was tested for its activity against S. aureus using the broth microdilution test; a crystal-violet biofilm assay was performed under a scanning electron microscope. The production of various virulence factors was estimated with PT13 treatment. Microarray gene expression profiling of PT13-treated S. aureus was conducted and compared with an untreated control. Exopolysaccharides (EPS) was estimated to observe the PT13 inhibition activity. Results: PT13 was antimicrobial toward S. aureus at different concentrations and showed a similar growth rate in the presence and absence of PT13 at concentrations ≤8 μg/mL. Biofilm production was interrupted even at low concentrations, and biofilm-related genes were down-regulated when exposed to PT13. The genes encoding cell adhesion and bacterial attachment protein were the major genes suppressed by PT13. In addition, hemolysins, clumping activity, and EPS production of S. aureus decreased after treatment in a concentration-dependent manner. Conclusions: A long-chain PT13 with effective actions that, even at low concentration levels, not only regulated the gene expression in the producer organism but also blocked the virulence gene expression in this Gram-positive human pathogen is described. Highlights: We identified a PT13 as a potential antivirulence agent that regulated production of bacterial virulence determinants (e.g., toxins, enzymes and biofilm), downwards and it may be a promising anti-virulence agent to be further developed as an anti-infective agent.

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Loss of Function inEscherichia coliExposed to Environmentally Relevant Concentrations of Benzalkonium Chloride

Applied and Environmental Microbiology ◽

10.1128/aem.02417-18 ◽

2018 ◽

Vol 85 (4) ◽

Cited By ~ 4

Author(s):

Sarah Forbes ◽

Nicola Morgan ◽

Gavin J. Humphreys ◽

Alejandro Amézquita ◽

Hitesh Mistry ◽

...

Keyword(s):

Escherichia Coli ◽

Growth Rate ◽

Biofilm Formation ◽

Benzalkonium Chloride ◽

Loss Of Function ◽

Free Medium ◽

Content Type ◽

Expression Of Genes ◽

Repeated Passage

ABSTRACTAssessing the risk of resistance associated with biocide exposure commonly involves exposing microorganisms to biocides at concentrations close to the MIC. With the aim of representing exposure to environmental biocide residues,Escherichia coliMG1655 was grown for 20 passages in the presence or absence of benzalkonium chloride (BAC) at 100 ng/liter and 1,000 ng/liter (0.0002% and 0.002% of the MIC, respectively). BAC susceptibility, planktonic growth rates, motility, and biofilm formation were assessed, and differentially expressed genes were determined via transcriptome sequencing. Planktonic growth rate and biofilm formation were significantly reduced (P< 0.001) following BAC adaptation, while BAC minimum bactericidal concentration increased 2-fold. Transcriptomic analysis identified 289 upregulated and 391 downregulated genes after long-term BAC adaptation compared with the respective control organism passaged in BAC-free medium. When the BAC-adapted bacterium was grown in BAC-free medium, 1,052 genes were upregulated and 753 were downregulated. Repeated passage solely in biocide-free medium resulted in 460 upregulated and 476 downregulated genes compared with unexposed bacteria. Long-term exposure to environmentally relevant BAC concentrations increased the expression of genes associated with efflux and reduced the expression of genes associated with outer-membrane porins, motility, and chemotaxis. This was manifested phenotypically through the loss of function (motility). Repeated passage in a BAC-free environment resulted in the upregulation of multiple respiration-associated genes, which was reflected by increased growth rate. In summary, repeated exposure ofE. colito BAC residues resulted in significant alterations in global gene expression that were associated with minor decreases in biocide susceptibility, reductions in growth rate and biofilm formation, and loss of motility.IMPORTANCEExposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in theEscherichia colitranscriptome. These results demonstrate the importance of including phenotypic characterization in studies designed to assess the risks of biocide exposure.

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Rethinking Pyogenic Flexor Tenosynovitis: Biofilm Formation Treated in a Cadaveric Model

Journal of Hand and Microsurgery ◽

10.1055/s-0037-1606625 ◽

2017 ◽

Vol 09 (03) ◽

pp. 131-138 ◽

Cited By ~ 3

Author(s):

Constantinos Ketonis ◽

Noreen Hickock ◽

Asif Ilyas

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Bacterial Colonization ◽

Bacterial Load ◽

Bacterial Attachment ◽

Laser Scanning Microscopy ◽

Local Antibiotics ◽

Saline Irrigation ◽

Pyogenic Flexor Tenosynovitis ◽

Flexor Tenosynovitis

Introduction Pyogenic flexor tenosynovitis (PFT) of the hand remains a challenging problem that often requires surgical irrigation and parenteral or oral antibiotics. The authors hypothesize that the pathophysiology and microenvironment of PFT can be likened to that of periprosthetic joint infections (PJIs), in which bacteria thrive in a closed synovial space with limited blood supply. As such, they postulate that PFT is also facilitated by bacterial attachment and biofilm formation rendering standard treatments less effective. In this study, they evaluate infected tendons for the presence of biofilm and explore new treatment strategies. Methods Fresh human cadaveric hand tendons were harvested and divided into 0.5-cm segments. Samples were sterilized and inoculated with 1 × 104 CFU/mL green fluorescent Staphylococcus aureus (GFP-SA) for 48 hours at 37°C. After saline washing to remove plank tonic bacteria, samples were treated for 24 hours with (1) saline irrigation, (2) antibiotics (vancomycin), (3) corticosteroids, or (4) antibiotics/corticosteroid combined. Samples were visualized using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Results Following bacterial challenge, CLSM revealed heterogeneous green fluorescence representing bacterial attachment with dense biofilm formation. SEM at > 3,000X, also demonstrated bacterial colonization in grape-like clusters consisted with a thick matrix characteristic of biofilm. Bacterial load by direct colony counting decreased by 18.5% with saline irrigation alone, 42.6% with steroids, 54.4% with antibiotics, and 77.3% with antibiotics/steroids combined (p < 0.05). Conclusion Staphylococcus aureus readily formed thick biofilm on human cadaveric tendons. The addition of both local antibiotics and corticosteroids resulted in greater decreases in biofilm formation on flexor tendons than the traditional treatment of saline irrigation alone. We suggest rethinking the current treatment of PFT and recommend considering a strategy more analogous to PJI management with the adjunctive use of local antibiotics, corticosteroids, and mechanical agitation.

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Methicillin-Resistant Staphylococcus aureus Grown on Vancomycin-Supplemented Screening Agar Displays Enhanced Biofilm Formation

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00568-15 ◽

2015 ◽

Vol 59 (12) ◽

pp. 7906-7910 ◽

Cited By ~ 5

Author(s):

Wenjiao Chang ◽

Ding Ding ◽

Shanshan Zhang ◽

Yuanyuan Dai ◽

Qing Pan ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Methicillin Resistant Staphylococcus Aureus ◽

Prolonged Exposure ◽

Brain Heart Infusion ◽

Polysaccharide Intercellular Adhesin ◽

Methicillin Resistant ◽

Content Type ◽

Brain Heart Infusion Agar ◽

Infusion Agar

ABSTRACTBrain heart infusion agar containing 3 mg/liter vancomycin (BHI-V3) was used to screen for heterogeneous vancomycin-intermediateStaphylococcus aureus(hVISA). There was markedly greater biofilm formation by isolates that grew on BHI-V3 than by strains that did not grow on BHI-V3. Increased biofilm formation by hVISA may be mediated by FnbA- and polysaccharide intercellular adhesin-dependent pathways, and upregulation ofatlAandsarAmay also contribute to enhanced biofilm formation by hVISA upon prolonged exposure to vancomycin.

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Correlation between mazEF Toxin-Antitoxin System Expression and Methicillin Susceptibility in Staphylococcus aureus and Its Relation to Biofilm-Formation

Microorganisms ◽

10.3390/microorganisms9112274 ◽

2021 ◽

Vol 9 (11) ◽

pp. 2274

Author(s):

Aya Abd El rahman ◽

Yasmine El kholy ◽

Rania Y. Shash

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Methicillin Resistance ◽

Diffusion Method ◽

P Value ◽

Sequence Motifs ◽

University Hospitals ◽

Specific Sequence ◽

Disk Diffusion Method ◽

Cellular Mrnas

Methicillin resistance in Staphylococcus aureus has become prevalent globally. Moreover, biofilm-formation makes it more difficult to eradicate bacteria by antibiotics. The mazEF toxin-antitoxin system encodes for mazF, which acts as an endoribonuclease that cleaves cellular mRNAs at specific sequence motifs (ACA), and mazE, which opposes the mazF action. Our goal was to detect mazEF expression in methicillin-resistant S. aureus (MRSA) isolates compared with methicillin-sensitive S. aureus (MSSA) isolates and determine its relation to methicillin susceptibility as well as biofilm-formation. According to their susceptibility to cefoxitin disks, 100 S. aureus isolates obtained from patients admitted to Cairo University Hospitals were categorized into 50 MSSA and 50 MRSA according to their susceptibility to cefoxitin disks (30 µg). Antimicrobial susceptibility and biofilm-formation were investigated using the disk diffusion method and tissue culture plate method, respectively. Finally, using real-time PCR, mazEF expression was estimated and correlated to methicillin susceptibility and biofilm formation. Both MRSA and MSSA isolates showed the best sensitivity results with linezolid and gentamicin, where about 88% of MRSA isolates and 96% of MSSA isolates were sensitive to linezolid while 76% of MRSA isolates and 84% of MSSA isolates were sensitive to gentamicin. MRSA isolates were significantly more able to form biofilm than MSSA isolates (p-value = 0.037). The mazEF expression was significantly correlated to methicillin resistance in S. aureus (p-value < 0.001), but not to biofilm-formation.

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The effects of NX-AS-401 on methicillin resistant Staphylococcus aureus

10.23889/suthesis.59037 ◽

2021 ◽

Author(s):

◽

Phillip Butterick

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Methicillin Resistant Staphylococcus Aureus ◽

Galleria Mellonella ◽

Standard Of Care ◽

Health Concern ◽

Current Standard ◽

Methicillin Resistant ◽

Biofilm Development ◽

Strain Dependent

Antimicrobial resistance is a global health concern, with once treatable infections becoming resistant to current standard of care antimicrobials. The search for new antimicrobials has led Neem Biotech Ltd. to manufacture NX-AS-401 an ajoene containing compound derived from Allium sativuum, commonly known as garlic. The research contained within this thesis aimed to identify the effects of NX-AS-401 on Methicillin Resistant Staphylococcus aureus (MRSA), one of the most well documented and commonly isolated antimicrobial resistant bacterial pathogens. A multi-stage approach was utilised, identifying how NX-AS-401 affects planktonic growth, biofilm development and virulence factor production. In Chapters 3 and 4 initial comparison between different NX-AS-401 formulations was performed in determined that ajoene content did not alter the antimicrobial effect of NX-AS-401. EUCAST broth microdilution compared NX-AS-401 to current standard of care antibiotic and determined effective inhibitory and bactericidal concentrations as 128 µg/ml and 2048 µg/ml respectively. When NX-AS-401 was used in combination with various antibiotic classes a synergistic effect was identified and the inhibitory concentrations of both agents were reduced. The primary focus on Chapter 5 was how NX-AS-401 affected S. aureus biofilm formation. NX-AS-401 concentrations of 32 µg/ml inhibited biofilm formation and a concentration of 512 µg/ml caused disruption of pre-established biofilms. These effects were confirmed using scanning electron microscopy and confocal microscopy with live/dead staining. In gene expression studies it was determined that the effects of NX-AS-401 on S. aureus biofilms were strain dependent and a target gene was not identified. Chapter 6 demonstrated that NX-AS-401 did not alter the production of Staphylococcus aureus exo-enzyme production in vitro during phenotypic studies. In Galleria mellonella low NX-AS-401 concentrations assisted in the recovery from S. aureus in a strain dependent manner, however, high concentrations caused increased Galleria mellonella fatality. NX-AS-401 altered the ability of S. aureus cells to invade human epithelial cells but did not prevent adhesion of S. aureus to the cells. NX-AS-401 has multiple effects on S. aureus with the ability to affect both planktonic cells and biofilm structure showing promise as an antimicrobial. Its main effects are growth inhibition and biofilm disruption rather than causing bacterial cell death. These attributes and the synergistic effects between NX-AS-401 and multiple antibiotic classes, indicate NX-AS-401 has potential as a strong antimicrobial adjuvant.

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Organoselenium Coating on Cellulose Inhibits the Formation of Biofilms by Pseudomonas aeruginosa and Staphylococcus aureus

Applied and Environmental Microbiology ◽

10.1128/aem.02683-08 ◽

2009 ◽

Vol 75 (11) ◽

pp. 3586-3592 ◽

Cited By ~ 65

Author(s):

Phat L. Tran ◽

Adrienne A. Hammond ◽

Thomas Mosley ◽

Janette Cortez ◽

Tracy Gray ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Pseudomonas Aeruginosa ◽

Biofilm Formation ◽

Bacterial Infections ◽

Antimicrobial Agents ◽

Bacterial Attachment ◽

Wound Dressings ◽

Aqueous Environment ◽

Burn Victims ◽

Surgical Wounds

ABSTRACT Among the most difficult bacterial infections encountered in treating patients are wound infections, which may occur in burn victims, patients with traumatic wounds, necrotic lesions in people with diabetes, and patients with surgical wounds. Within a wound, infecting bacteria frequently develop biofilms. Many current wound dressings are impregnated with antimicrobial agents, such as silver or antibiotics. Diffusion of the agent(s) from the dressing may damage or destroy nearby healthy tissue as well as compromise the effectiveness of the dressing. In contrast, the antimicrobial agent selenium can be covalently attached to the surfaces of a dressing, prolonging its effectiveness. We examined the effectiveness of an organoselenium coating on cellulose discs in inhibiting Pseudomonas aeruginosa and Staphylococcus aureus biofilm formation. Colony biofilm assays revealed that cellulose discs coated with organoselenium completely inhibited P. aeruginosa and S. aureus biofilm formation. Scanning electron microscopy of the cellulose discs confirmed these results. Additionally, the coating on the cellulose discs was stable and effective after a week of incubation in phosphate-buffered saline. These results demonstrate that 0.2% selenium in a coating on cellulose discs effectively inhibits bacterial attachment and biofilm formation and that, unlike other antimicrobial agents, longer periods of exposure to an aqueous environment do not compromise the effectiveness of the coating.

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