Antibiotic penetration and bacterial killing in a<i>Pseudomonas aeruginosa</i>biofilm model

Cao, Bao; Christophersen, Lars; Thomsen, Kim; Sønderholm, Majken; Bjarnsholt, Thomas; Jensen, Peter Østrup; Høiby, Niels; Moser, Claus

doi:10.1093/jac/dkv058

Cited by 57 publications

(47 citation statements)

References 29 publications

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“…9D). This confirmed that tobramycin is capable of penetrating the alginate beads (55) and that the effect of tobramycin is dependent on the physiological growth stage of P. aeruginosa rather than on transport limitation.…”

Section: Discussionsupporting

confidence: 68%

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Sønderholm

Kragh

Koren

et al. 2017

Appl Environ Microbiol

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124

113

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Alginate beads represent a simple and highly reproducible in vitro model system for diffusion-limited bacterial growth. In this study, alginate beads were inoculated with Pseudomonas aeruginosa and followed for up to 72 h. Confocal microscopy revealed that P. aeruginosa formed dense clusters similar in size to in vivo aggregates observed ex vivo in cystic fibrosis lungs and chronic wounds. Bacterial aggregates primarily grew in the bead periphery and decreased in size and abundance toward the center of the bead. Microsensor measurements showed that the O2 concentration decreased rapidly and reached anoxia ∼100 μm below the alginate bead surface. This gradient was relieved in beads supplemented with NO3− as an alternative electron acceptor allowing for deeper growth into the beads. A comparison of gene expression profiles between planktonic and alginate-encapsulated P. aeruginosa confirmed that the bacteria experienced hypoxic and anoxic growth conditions. Furthermore, alginate-encapsulated P. aeruginosa exhibited a lower respiration rate than the planktonic counterpart and showed a high tolerance toward antibiotics. The inoculation and growth of P. aeruginosa in alginate beads represent a simple and flexible in vivo-like biofilm model system, wherein bacterial growth exhibits central features of in vivo biofilms. This was observed by the formation of small cell aggregates in a secondary matrix with O2-limited growth, which was alleviated by the addition of NO3− as an alternative electron acceptor, and by reduced respiration rates, as well as an enhanced tolerance to antibiotic treatment.IMPORTANCE Pseudomonas aeruginosa has been studied intensively for decades due to its involvement in chronic infections, such as cystic fibrosis and chronic wounds, where it forms biofilms. Much research has been dedicated to biofilm formation on surfaces; however, in chronic infections, most biofilms form small aggregates of cells not attached to a surface, but embedded in host material. In this study, bacteria were encapsulated in small alginate beads and formed aggregates similar to what is observed in chronic bacterial infections. Our findings show that aggregates are exposed to steep oxygen gradients, with zones of oxygen depletion, and that nitrate may serve as an alternative to oxygen, enabling growth in oxygen-depleted zones. This is important, as slow growth under low-oxygen conditions may render the bacteria tolerant toward antibiotics. This model provides an alternative to surface biofilm models and adds to the comprehension that biofilms do not depend on a surface for formation.

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Section: Discussionsupporting

confidence: 68%

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Sønderholm

Kragh

Koren

et al. 2017

Appl Environ Microbiol

Self Cite

124

113

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“…Efforts on designing PK/PD studies and analysis that resemble the behavior of antibiotics on human body have been intensively carried out recently. For instance, as conceptually, biofilms may be considered as independent compartment with particular pharmacokinetics, Cao et al (21) studied the PK/PD of tobramycin in seaweed alginate-embedded biofilms providing a model for testing new treatment strategies. In another recent work, a new in vitro PK/PD simulator using flow cell technology and CLSM has been employed on P. aeruginosa laboratory and clinical strain biofilms to study the antibacterial activity of meropenem (76).…”

Section: Susceptibility Testing and Pk/pd In Biofilmsmentioning

confidence: 99%

Antibiotic treatment of biofilm infections

Ciofu

Rojo-Molinero²,

Macià³

et al. 2017

APMIS

334

259

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Bacterial biofilms are associated with a wide range of infections, from those related to exogenous devices, such as catheters or prosthetic joints, to chronic tissue infections such as those occurring in the lungs of cystic fibrosis patients. Biofilms are recalcitrant to antibiotic treatment due to multiple tolerance mechanisms (phenotypic resistance). This causes persistence of biofilm infections in spite of antibiotic exposure which predisposes to antibiotic resistance development (genetic resistance). Understanding the interplay between phenotypic and genetic resistance mechanisms acting on biofilms, as well as appreciating the diversity of environmental conditions of biofilm infections which influence the effect of antibiotics are required in order to optimize the antibiotic treatment of biofilm infections. Here, we review the current knowledge on phenotypic and genetic resistance in biofilms and describe the potential strategies for the antibiotic treatment of biofilm infections. Of note is the optimization of PK/PD parameters in biofilms, high-dose topical treatments, combined and sequential/alternate therapies or the use antibiotic adjuvants.

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“…The EPS also contains DNA and, in the case of mucoid strains, high levels of the polyanionic aminoglycoside-binding alginate, although alginate surprisingly seems to not significantly hinder penetration. 107–109 …”

Section: Interactive Filtersmentioning

confidence: 99%

The particle in the spider's web: transport through biological hydrogels

2017

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Biological hydrogels such as mucus, extracellular matrix, biofilms, and the nuclear pore have diverse functions and compositions, but all act as selectively permeable barriers to the diffusion of particles. Each barrier has a crosslinked polymeric mesh that blocks penetration of large particles such as pathogens, nanotherapeutics, or macromolecules. These polymeric meshes also employ interactive filtering, in which affinity between solutes and the gel matrix controls permeability. Interactive filtering affects the transport of particles of all sizes including peptides, antibiotics, and nanoparticles and in many cases this filtering can be described in terms of the effects of charge and hydrophobicity. The concepts described in this review can guide strategies to exploit or overcome gel barriers, particularly for applications in diagnostics, pharmacology, biomaterials, and drug delivery.

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Antibiotic penetration and bacterial killing in aPseudomonas aeruginosabiofilm model

Cited by 57 publications

References 29 publications

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Pseudomonas aeruginosa Aggregate Formation in an Alginate Bead Model System Exhibits In Vivo -Like Characteristics

Antibiotic treatment of biofilm infections

The particle in the spider's web: transport through biological hydrogels

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