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Nahum Y, Gross N, Cerrone A, Matouš K, Nerenberg R. Effect of biofilm physical characteristics on their susceptibility to antibiotics: impacts of low-frequency ultrasound. NPJ Biofilms Microbiomes 2024; 10:70. [PMID: 39160204 DOI: 10.1038/s41522-024-00544-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Accepted: 07/31/2024] [Indexed: 08/21/2024] Open
Abstract
Biofilms are highly resistant to antimicrobials, often causing chronic infections. Combining antimicrobials with low-frequency ultrasound (LFU) enhances antimicrobial efficiency, but little is known about the underlying mechanisms. Biofilm physical characteristics, which depend on factors such as growth conditions and age, can have significant effects on inactivation efficiency. In this study, we investigated the susceptibility of Pseudomonas aeruginosa biofilms to tobramycin, with and without LFU treatment. The biofilms were grown under low and high fluid shear to provide different characteristics. Low-shear biofilms exhibited greater thickness, roughness, and porosity and lower density, compared to high-shear biofilms. The biofilm matrix of the high-shear biofilms had a three times higher protein-to-polysaccharide ratio, suggesting greater biofilm stiffness. This was supported by microrheology measurements of biofilm creep compliance. For the low-shear biofilms without LFU, the viability of the biofilms in their inner regions was largely unaffected by the antibiotic after a 2-hour treatment. However, when tobramycin was combined with LFU, the inactivation for the entire biofilm increased to 80% after 2 h. For the high-shear biofilms without LFU, higher LFU intensities were needed to achieve similar inactivation results. Microrheology measurements revealed that changes in biofilm inactivation profiles were closely related to changes in biofilm mechanical properties. Modeling suggests that LFU changes antibiotic diffusivity within the biofilm, probably due to a "decohesion" effect. Overall, this research suggests that biofilm physical characteristics (e.g., compliance, morphology) are linked to antimicrobial efficiency. LFU weakens the biofilm while increasing its diffusivity for antibiotics.
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Affiliation(s)
- Yanina Nahum
- University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, IN, USA
| | - Neila Gross
- Boston University, Department of Materials Science and Engineering, Boston, MA, USA
| | - Albert Cerrone
- University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, IN, USA
| | - Karel Matouš
- University of Notre Dame, Department of Aerospace and Mechanical Engineering, Notre Dame, IN, USA
| | - Robert Nerenberg
- University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, Notre Dame, IN, USA.
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Yakoup AY, Kamel AG, Elbermawy Y, Abdelsattar AS, El-Shibiny A. Characterization, antibacterial, and cytotoxic activities of silver nanoparticles using the whole biofilm layer as a macromolecule in biosynthesis. Sci Rep 2024; 14:364. [PMID: 38172225 PMCID: PMC10764356 DOI: 10.1038/s41598-023-50548-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 12/21/2023] [Indexed: 01/05/2024] Open
Abstract
Recently, multi-drug resistant (MDR) bacteria are responsible for a large number of infectious diseases that can be life-threatening. Globally, new approaches are targeted to solve this essential issue. This study aims to discover novel antibiotic alternatives by using the whole components of the biofilm layer as a macromolecule to synthesize silver nanoparticles (AgNPs) as a promising agent against MDR. In particular, the biosynthesized biofilm-AgNPs were characterized using UV-Vis spectroscopy, electron microscopes, Energy Dispersive X-ray (EDX), zeta sizer and potential while their effect on bacterial strains and normal cell lines was identified. Accordingly, biofilm-AgNPs have a lavender-colored solution, spherical shape, with a size range of 20-60 nm. Notably, they have inhibitory effects when used on various bacterial strains with concentrations ranging between 12.5 and 25 µg/mL. In addition, they have an effective synergistic effect when combined with phage ZCSE9 to inhibit and kill Salmonella enterica with a concentration of 3.1 µg/mL. In conclusion, this work presents a novel biosynthesis preparation of AgNPs using biofilm for antibacterial purposes to reduce the possible toxicity by reducing the MICs using phage ZCSE9.
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Affiliation(s)
- Aghapy Yermans Yakoup
- Center for Microbiology and Phage Therapy, Zewail City of Science and Technology, Giza, 12578, Egypt
| | - Azza G Kamel
- Center for Microbiology and Phage Therapy, Zewail City of Science and Technology, Giza, 12578, Egypt
| | - Yasmin Elbermawy
- Center for Microbiology and Phage Therapy, Zewail City of Science and Technology, Giza, 12578, Egypt
| | - Abdallah S Abdelsattar
- Center for Microbiology and Phage Therapy, Zewail City of Science and Technology, Giza, 12578, Egypt
| | - Ayman El-Shibiny
- Center for Microbiology and Phage Therapy, Zewail City of Science and Technology, Giza, 12578, Egypt.
- Faculty of Environmental Agricultural Sciences, Arish University, Arish, 45511, Egypt.
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Wells M, Schneider R, Bhattarai B, Currie H, Chavez B, Christopher G, Rumbaugh K, Gordon V. Perspective: The viscoelastic properties of biofilm infections and mechanical interactions with phagocytic immune cells. Front Cell Infect Microbiol 2023; 13:1102199. [PMID: 36875516 PMCID: PMC9978752 DOI: 10.3389/fcimb.2023.1102199] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 01/24/2023] [Indexed: 02/18/2023] Open
Abstract
Biofilms are viscoelastic materials that are a prominent public health problem and a cause of most chronic bacterial infections, in large part due to their resistance to clearance by the immune system. Viscoelastic materials combine both solid-like and fluid-like mechanics, and the viscoelastic properties of biofilms are an emergent property of the intercellular cohesion characterizing the biofilm state (planktonic bacteria do not have an equivalent property). However, how the mechanical properties of biofilms are related to the recalcitrant disease that they cause, specifically to their resistance to phagocytic clearance by the immune system, remains almost entirely unstudied. We believe this is an important gap that is ripe for a large range of investigations. Here we present an overview of what is known about biofilm infections and their interactions with the immune system, biofilm mechanics and their potential relationship with phagocytosis, and we give an illustrative example of one important biofilm-pathogen (Pseudomonas aeruginosa) which is the most-studied in this context. We hope to inspire investment and growth in this relatively-untapped field of research, which has the potential to reveal mechanical properties of biofilms as targets for therapeutics meant to enhance the efficacy of the immune system.
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Affiliation(s)
- Marilyn Wells
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX, United States
| | - Rebecca Schneider
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Bikash Bhattarai
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX, United States
| | - Hailey Currie
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX, United States
| | - Bella Chavez
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX, United States
| | - Gordon Christopher
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX, United States
| | - Kendra Rumbaugh
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Vernita Gordon
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX, United States
- LaMontagne Center for Infectious Disease, The University of Texas at Austin, Austin, TX, United States
- Interdisciplinary Life Sciences Graduate Program, The University of Texas at Austin, Austin, TX, United States
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Li M, Nahum Y, Matouš K, Stoodley P, Nerenberg R. Effects of biofilm heterogeneity on the apparent mechanical properties obtained by shear rheometry. Biotechnol Bioeng 2023; 120:553-561. [PMID: 36305479 DOI: 10.1002/bit.28276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Revised: 09/30/2022] [Accepted: 10/24/2022] [Indexed: 01/13/2023]
Abstract
Rheometry is an experimental technique widely used to determine the mechanical properties of biofilms. However, it characterizes the bulk mechanical behavior of the whole biofilm. The effects of biofilm mechanical heterogeneity on rheometry measurements are not known. We used laboratory experiments and computer modeling to explore the effects of biofilm mechanical heterogeneity on the results obtained by rheometry. A synthetic biofilm with layered mechanical properties was studied, and a viscoelastic biofilm theory was employed using the Kelvin-Voigt model. Agar gels with different concentrations were used to prepare the layered, heterogeneous biofilm, which was characterized for mechanical properties in shear mode with a rheometer. Both experiments and simulations indicated that the biofilm properties from rheometry were strongly biased by the weakest portion of the biofilm. The simulation results using linearly stratified mechanical properties from a previous study also showed that the weaker portions of the biofilm dominated the mechanical properties in creep tests. We note that the model can be used as a predictive tool to explore the mechanical behavior of complex biofilm structures beyond those accessible to experiments. Since most biofilms display some degree of mechanical heterogeneity, our results suggest caution should be used in the interpretation of rheometry data. It does not necessarily provide the "average" mechanical properties of the entire biofilm if the mechanical properties are stratified.
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Affiliation(s)
- Mengfei Li
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Yanina Nahum
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Karel Matouš
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, USA
| | - Paul Stoodley
- Department of Microbial Infection and Immunity, The Ohio State University, Columbus, Ohio, USA
- National Biofilm Innovation Centre (NBIC) and National Centre for Advanced Tribology at Southampton (nCATS), Mechanical Engineering, University of Southampton, Southampton, United Kingdom
| | - Robert Nerenberg
- Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana, USA
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Dynamic Changes in Biofilm Structures under Dynamic Flow Conditions. Appl Environ Microbiol 2022; 88:e0107222. [PMID: 36300948 PMCID: PMC9680615 DOI: 10.1128/aem.01072-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Detachment is an important process determining the structure and function of bacterial biofilm, which has significant implications for biogeochemical cycling of elements, biofilm application, and infection control in clinical settings. Quantifying the responses of biofilm structure to hydrodynamics is crucial for understanding biofilm detachment mechanisms in aquatic environments.
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Li M, Matouš K, Nerenberg R. Data-driven modeling of heterogeneous viscoelastic biofilms. Biotechnol Bioeng 2022; 119:1301-1313. [PMID: 35129209 DOI: 10.1002/bit.28056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 01/21/2022] [Accepted: 01/30/2022] [Indexed: 11/06/2022]
Abstract
Biofilms are typically heterogeneous in morphology, structure, and composition, resulting in non-uniform mechanical properties. The distribution of mechanical properties, in turn, determines the biofilm behavior, such as deformation and detachment. Most biofilm models neglect biofilm heterogeneity, especially at the microscale. In this study, an image-based modeling approach was developed to transform two-dimensional optical coherence tomography (OCT) biofilm images to a pixel-scale non-Newtonian viscosity map of the biofilm. The map was calibrated using the bulk viscosity data from rheometer tests, based on assumed maximum and minimum viscosities and a relationship between OCT image intensity signals and non-Newtonian viscosity. While not quantitatively measuring biofilm viscosity for each pixel, it allows a rational spatial allocation of viscosities within the biofilm: areas with lower cell density, e.g., voids, are assigned lower viscosities, and areas with high cell densities are assigned higher viscosities. The spatial distribution of non-Newtonian viscosity was applied in an established Oldroyd-B constitutive model and implemented using the phase-field continuum approach for the deformation and stress analysis. The heterogeneous model was able to predict deformations more accurately than a homogenous one. Stress distribution in the heterogeneous biofilm displayed better characteristics than that in the homogeneous one, because it is highly dependent on the viscosity distribution. This work, using a pixel-scale, image-based approach to map the mechanical heterogeneity of biofilms for computational deformation and stress analysis, provides a novel modeling approach that allows the consideration of biofilm structural and mechanical heterogeneity. Future research should better characterize the relationship between OCT signal and viscosity, and consider other constitutive models for biofilm mechanical behavior. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Mengfei Li
- University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, 156 Fitzpatrick Hall, Notre Dame, IN, 46556, USA
| | - Karel Matouš
- University of Notre Dame, Department of Aerospace and Mechanical Engineering, Notre Dame, IN, 46556, USA
| | - Robert Nerenberg
- University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, 156 Fitzpatrick Hall, Notre Dame, IN, 46556, USA
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