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Journal ArticleDOI

The extracellular matrix protects Pseudomonas aeruginosa biofilms by limiting the penetration of tobramycin.

TL;DR: It is proposed that tobramycin sequestration at the biofilm periphery is an important mechanism in protecting metabolically active cells that lie just below the zone of sequestration.
Abstract: Biofilm cells are less susceptible to antimicrobials than their planktonic counterparts. While this phenomenon is multifactorial, the ability of the matrix to reduce antibiotic penetration into the biofilm is thought to be of limited importance studies suggest that antibiotics move fairly rapidly through biofilms. In this study, we monitored the transport of two clinically relevant antibiotics, tobramycin and ciprofloxacin, into non-mucoid Pseudomonas aeruginosa biofilms. To our surprise, we found that the positively charged antibiotic tobramycin is sequestered to the biofilm periphery, while the neutral antibiotic ciprofloxacin readily penetrated. We provide evidence that tobramycin in the biofilm periphery both stimulated a localized stress response and killed bacteria in these regions but not in the underlying biofilm. Although it is unclear which matrix component binds tobramycin, its penetration was increased by the addition of cations in a dose-dependent manner, which led to increased biofilm death. These data suggest that ionic interactions of tobramycin with the biofilm matrix limit its penetration. We propose that tobramycin sequestration at the biofilm periphery is an important mechanism in protecting metabolically active cells that lie just below the zone of sequestration.
Citations
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Journal ArticleDOI
TL;DR: This review summarises both historical and recent scientific data in support of the known biofilm resistance and tolerance mechanisms and suggestions for future work in the field are provided.
Abstract: Biofilms are surface-attached groups of microbial cells encased in an extracellular matrix that are significantly less susceptible to antimicrobial agents than non-adherent, planktonic cells. Biofilm-based infections are, as a result, extremely difficult to cure. A wide range of molecular mechanisms contribute to the high degree of recalcitrance that is characteristic of biofilm communities. These mechanisms include, among others, interaction of antimicrobials with biofilm matrix components, reduced growth rates and the various actions of specific genetic determinants of antibiotic resistance and tolerance. Alone, each of these mechanisms only partially accounts for the increased antimicrobial recalcitrance observed in biofilms. Acting in concert, however, these defences help to ensure the survival of biofilm cells in the face of even the most aggressive antimicrobial treatment regimens. This review summarises both historical and recent scientific data in support of the known biofilm resistance and tolerance mechanisms. Additionally, suggestions for future work in the field are provided.

956 citations

Journal ArticleDOI
TL;DR: This review presents the current understanding of the molecular mechanisms of biofilm recalcitrance toward antibiotics and describes how recent progress has improved the capacity to design original and efficient strategies to prevent or eradicate biofilm-related infections.
Abstract: Surface-associated microbial communities, called biofilms, are present in all environments. Although biofilms play an important positive role in a variety of ecosystems, they also have many negative effects, including biofilm-related infections in medical settings. The ability of pathogenic biofilms to survive in the presence of high concentrations of antibiotics is called "recalcitrance" and is a characteristic property of the biofilm lifestyle, leading to treatment failure and infection recurrence. This review presents our current understanding of the molecular mechanisms of biofilm recalcitrance toward antibiotics and describes how recent progress has improved our capacity to design original and efficient strategies to prevent or eradicate biofilm-related infections.

862 citations


Cites background from "The extracellular matrix protects P..."

  • ...aeruginosa biofilm, tobramycin was shown to exhibit delayed and reduced diffusion in vitro (41, 42)....

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Journal ArticleDOI
01 Dec 2018-Heliyon
TL;DR: A brief overview of concepts of bacterial biofilm formation, current state-of-the-art therapeutic approaches for preventing and treating biofilms, and the prevalence of such infections on medical devices is reviewed.

623 citations

Journal ArticleDOI
TL;DR: The mechanisms by which nanomaterials can be used to target antibiotic-resistant bacterial infections are discussed, design elements and properties of nanomMaterials that can be engineered to enhance potency are highlighted, and recent progress and remaining challenges for clinical implementation are explored.
Abstract: Antibiotic-resistant bacterial infections arising from acquired resistance and/or through biofilm formation necessitate the development of innovative 'outside of the box' therapeutics Nanomaterial-based therapies are promising tools to combat bacterial infections that are difficult to treat, featuring the capacity to evade existing mechanisms associated with acquired drug resistance In addition, the unique size and physical properties of nanomaterials give them the capability to target biofilms, overcoming recalcitrant infections In this Review, we highlight the general mechanisms by which nanomaterials can be used to target bacterial infections associated with acquired antibiotic resistance and biofilms We emphasize design elements and properties of nanomaterials that can be engineered to enhance potency Lastly, we present recent progress and remaining challenges for widespread clinical implementation of nanomaterials as antimicrobial therapeutics

418 citations

Journal ArticleDOI
TL;DR: Three mechanisms that play an important role in biofilm survival are discussed, found both in bacterial and fungal biofilms and are often surprisingly similar between distantly related organisms.

399 citations

References
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Journal ArticleDOI
21 May 1999-Science
TL;DR: Improvements in understanding of the genetic and molecular basis of bacterial community behavior point to therapeutic targets that may provide a means for the control of biofilm infections.
Abstract: Bacteria that attach to surfaces aggregate in a hydrated polymeric matrix of their own synthesis to form biofilms. Formation of these sessile communities and their inherent resistance to antimicrobial agents are at the root of many persistent and chronic bacterial infections. Studies of biofilms have revealed differentiated, structured groups of cells with community properties. Recent advances in our understanding of the genetic and molecular basis of bacterial community behavior point to therapeutic targets that may provide a means for the control of biofilm infections.

11,162 citations


"The extracellular matrix protects P..." refers background in this paper

  • ...Therefore, the physical and physiological 30 attributes of the biofilm growth environment protect resident cells from the lethal action 31 of antimicrobials (Costerton et al., 1999)....

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Journal ArticleDOI
TL;DR: In this paper, a new vector strategy for the insertion of foreign genes into the genomes of gram negative bacteria not closely related to Escherichia coli was developed, which can utilize any gram negative bacterium as a recipient for conjugative DNA transfer.
Abstract: We have developed a new vector strategy for the insertion of foreign genes into the genomes of gram negative bacteria not closely related to Escherichia coli. The system consists of two components: special E. coli donor strains and derivatives of E. coli vector plasmids. The donor strains (called mobilizing strains) carry the transfer genes of the broad host range IncP–type plasmid RP4 integrated in their chromosomes. They can utilize any gram negative bacterium as a recipient for conjugative DNA transfer. The vector plasmids contain the P–type specific recognition site for mobilization (Mob site) and can be mobilized with high frequency from the donor strains. The mobilizable vectors are derived from the commonly used E. coli vectors pACYC184, pACYC177, and pBR325, and are unable to replicate in strains outside the enteric bacterial group. Therefore, they are widely applicable as transposon carrier replicons for random transposon insertion mutagenesis in any strain into which they can be mobilized but not stably maintained. The vectors are especially useful for site–directed transposon mutagenesis and for site–specific gene transfer in a wide variety of gram negative organisms.

7,278 citations

Journal ArticleDOI
TL;DR: Minimal biofilm eradication concentrations, derived by using the Calgary Biofilm Device, demonstrated that for biofilms of the same organisms, 100 to 1,000 times the concentration of a certain antibiotic were often required for the antibiotic to be effective, while other antibiotics were found to beeffective at the MICs.
Abstract: Determination of the MIC, based on the activities of antibiotics against planktonic bacteria, is the standard assay for antibiotic susceptibility testing. Adherent bacterial populations (biofilms) present with an innate lack of antibiotic susceptibility not seen in the same bacteria grown as planktonic populations. The Calgary Biofilm Device (CBD) is described as a new technology for the rapid and reproducible assay of biofilm susceptibilities to antibiotics. The CBD produces 96 equivalent biofilms for the assay of antibiotic susceptibilities by the standard 96-well technology. Biofilm formation was followed by quantitative microbiology and scanning electron microscopy. Susceptibility to a standard group of antibiotics was determined for National Committee for Clinical Laboratory Standards (NCCLS) reference strains: Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Staphylococcus aureus ATCC 29213. Growth curves demonstrated that biofilms of a predetermined size could be formed on the CBD at specific time points and, furthermore, that no significant difference (P > 0.1) was seen between biofilms formed on each of the 96 pegs. The antibiotic susceptibilities for planktonic populations obtained by the NCCLS method or from the CBD were similar. Minimal biofilm eradication concentrations, derived by using the CBD, demonstrated that for biofilms of the same organisms, 100 to 1,000 times the concentration of a certain antibiotic were often required for the antibiotic to be effective, while other antibiotics were found to be effective at the MICs. The CBD offers a new technology for the rational selection of antibiotics effective against microbial biofilms and for the screening of new effective antibiotic compounds.

1,880 citations


"The extracellular matrix protects P..." refers methods in this paper

  • ...432 433 MBEC viability assay 434 Biofilms were cultivated in the Calgary Biofilm Device (MBEC™ Physiology and 435 Genetics Assay, Innovotech Inc.) as described previously (Ceri et al., 1999; Harrison et 436 al., 2010)....

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Journal ArticleDOI
30 Jun 1995-Science
TL;DR: A Pseudomonas aeruginosa strain (UCBPP-PA14) is infectious both in an Arabidopsis thaliana leaf infiltration model and in a mouse full-thickness skin burn model, indicating that these genes encode virulence factors required for the full expression of pathogenicity in both plants and animals.
Abstract: A Pseudomonas aeruginosa strain (UCBPP-PA14) is infectious both in an Arabidopsis thaliana leaf infiltration model and in a mouse full-thickness skin burn model. UCBPP-PA14 exhibits ecotype specificity for Arabidopsis, causing a range of symptoms from none to severe in four different ecotypes. In the mouse model, UCBPP-PA14 is as lethal as other well-studied P. aeruginosa strains. Mutations in the UCBPP-PA14 toxA, plcS, and gacA genes resulted in a significant reduction in pathogenicity in both hosts, indicating that these genes encode virulence factors required for the full expression of pathogenicity in both plants and animals.

1,297 citations

Journal ArticleDOI
TL;DR: Disabling biofilm resistance may enhance the ability of existing antibiotics to clear infections involving biofilms that are refractory to current treatments.

1,202 citations


"The extracellular matrix protects P..." refers background in this paper

  • ...Moreover, the 28 antibiotic susceptibility of biofilm bacteria returns upon dispersion of the biofilm cells 29 back to the planktonic state (Stewart, 2002)....

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  • ...…1992; Dunne et al., 1993; Yasuda et al., 1993; Kumon et 60 al., 1994; Suci et al., 1994; Shigeta et al., 1997; Vrany et al., 1997; Anderl et al., 2000; 61 Stone et al., 2002; Zheng and Stewart, 2002; Walters et al., 2003; Jefferson et al., 2005; 62 Singh et al., 2010; Ortiz-Perez et al., 2011)....

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  • ...While heightened tolerance is clearly due to multiple mechanisms 284 (Stewart, 2002), here we showed that non-mucoid P. aeruginosa biofilms protect 285 resident cells by limiting the penetration of tobramycin via ionic interactions with the 286 biofilm....

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  • ...While heightened tolerance is clearly due to multiple mechanisms 284 (Stewart, 2002), here we showed that non-mucoid P....

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