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Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria

View Article: PubMed Central - PubMed

ABSTRACT

Antibiotic resistant bacteria not only affect human health and but also threatens the safety in hospitals and among communities. However, the emergence of drug resistant bacteria is inevitable due to evolutionary selection as a consequence of indiscriminate antibiotic usage. Therefore, it is necessary to develop a novel strategy by which pathogenic bacteria can be eliminated without triggering resistance. We propose a novel magnetic nanoparticle-based physical treatment against pathogenic bacteria, which blocks biofilm formation and kills bacteria. In this approach, multiple drug resistant Staphylococcus aureus USA300 and uropathogenic Escherichia coli CFT073 are trapped to the positively charged magnetic core-shell nanoparticles (MCSNPs) by electrostatic interaction. All the trapped bacteria can be completely killed within 30 min owing to the loss of membrane potential and dysfunction of membrane-associated complexes when exposed to the radiofrequency current. These results indicate that MCSNP-based physical treatment can be an alternative antibacterial strategy without leading to antibiotic resistance, and can be used for many purposes including environmental and therapeutic applications.

No MeSH data available.


Inhibition of UPEC biofilm formation by MCSNPs.(a) Biofilm formation by wild type UPEC, mutant (∆fimAΩkmr), and complemented (∆fimAΩkmr::pQE30fimA) strains is quantitatively analyzed by staining with crystal violet and measuring the absorbance 550 nm. Insets display the biofilm in tubes. Top view and Z-stack images of biofilm formed by wild type UPEC without (b, b’) and with MCSNP (c, c’), and ∆fimAΩkmr strains without (d, d’) and with MCSNP (e, e’). The samples were stained by fluorescein diacetate and propidium iodide before examination with confocal laser scanning microscopy. The biofilm thicknesses in b’–e’ were calculated to be 28, 6, 6, and 3.5 μM, respectively. (f) Schematic diagram showing the role of type I fimbriae in biofilm formation (top), inhibition of biofilm formation by MCSNPs (bottom), and failure of biofilm formation in the ∆fimA strains (middle).
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f3: Inhibition of UPEC biofilm formation by MCSNPs.(a) Biofilm formation by wild type UPEC, mutant (∆fimAΩkmr), and complemented (∆fimAΩkmr::pQE30fimA) strains is quantitatively analyzed by staining with crystal violet and measuring the absorbance 550 nm. Insets display the biofilm in tubes. Top view and Z-stack images of biofilm formed by wild type UPEC without (b, b’) and with MCSNP (c, c’), and ∆fimAΩkmr strains without (d, d’) and with MCSNP (e, e’). The samples were stained by fluorescein diacetate and propidium iodide before examination with confocal laser scanning microscopy. The biofilm thicknesses in b’–e’ were calculated to be 28, 6, 6, and 3.5 μM, respectively. (f) Schematic diagram showing the role of type I fimbriae in biofilm formation (top), inhibition of biofilm formation by MCSNPs (bottom), and failure of biofilm formation in the ∆fimA strains (middle).

Mentions: Since fimbriae are known to be main players in biofilm formation3132, we further characterized the phenotype of the ∆fimA strain by investigating its biofilm formation on polypropylene substrate using the crystal violet staining. The ∆fimA strain showed only 12.5% biofilm formation capacity compared to the wild type and complemented strains (Fig. 3a), confirming fimbriae have a primary role in UPEC biofilm formation as reported earlier in the other commensal E. coli strain31. Accordingly, we hypothesized that bacteria treated with MCSNPs show reduced biofilm formation capacity since MCSNP binding to fimbriae possibly blocks fimbriae-surface and fimbriae-fimbriae interactions, which are the key steps and prerequisites of biofilm formation. The fluorescein diacetate (FDA) and propidium iodide (PI) stained biofilms of wild type and ∆fimA UPEC without or with MCSNP were analyzed by confocal microscopy (Fig. 3b–e) and biofilm thickness was analyzed by z-stack image where one stack is equivalent to 1 μm (Fig. 3b’–e’). As expected, wild type UPEC produced the thickest biofilm, up to 28 μm, when MCSNP was absent (Fig. 3b–b’). However, treatment of MCSNP to the wild type UPEC reduced the biofilm thickness to 6 μm (Fig. 3c–c’), which was similar to that of ∆fimA strain (Fig. 3d–d’). The treatment of MCSNPs to the ∆fimA strain further reduced the biofilm thickness of ∆fimA strain to 3.5 μm (Fig. 3e–e’). These results suggest that MCSNP can also block biofilm formation mediated by other factors in addition to fimbriae. MCSNP treatment resulted in a 78.6% reduction in biofilm thickness of wild type UPEC. Significant reduction in biofilm thickness owing to the treatment with MCSNP is likely achieved due to the unavailability of free fimbriae required for the interaction with a surface for bacterial attachment. Taken together, these results indicate that the MCSNP-trapped wild type UPEC possesses the cell surface analogy with the ∆fimA strain by having fimbriae buried inside MCSNP. Accordingly, MCSNP can effectively block biofilm formation by inhibiting cell-cell interactions within the community. The schematic diagram showing biofilm formation by wild type UPEC and ∆fimA with and without MCSNP is depicted in Fig. 3f where the wild type strain formed a thicker biofilm and consequently creates a stronger physical barrier to drug entry than ∆fimA or MCSNP-complexed WT strain.


Coupling of radiofrequency with magnetic nanoparticles treatment as an alternative physical antibacterial strategy against multiple drug resistant bacteria
Inhibition of UPEC biofilm formation by MCSNPs.(a) Biofilm formation by wild type UPEC, mutant (∆fimAΩkmr), and complemented (∆fimAΩkmr::pQE30fimA) strains is quantitatively analyzed by staining with crystal violet and measuring the absorbance 550 nm. Insets display the biofilm in tubes. Top view and Z-stack images of biofilm formed by wild type UPEC without (b, b’) and with MCSNP (c, c’), and ∆fimAΩkmr strains without (d, d’) and with MCSNP (e, e’). The samples were stained by fluorescein diacetate and propidium iodide before examination with confocal laser scanning microscopy. The biofilm thicknesses in b’–e’ were calculated to be 28, 6, 6, and 3.5 μM, respectively. (f) Schematic diagram showing the role of type I fimbriae in biofilm formation (top), inhibition of biofilm formation by MCSNPs (bottom), and failure of biofilm formation in the ∆fimA strains (middle).
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f3: Inhibition of UPEC biofilm formation by MCSNPs.(a) Biofilm formation by wild type UPEC, mutant (∆fimAΩkmr), and complemented (∆fimAΩkmr::pQE30fimA) strains is quantitatively analyzed by staining with crystal violet and measuring the absorbance 550 nm. Insets display the biofilm in tubes. Top view and Z-stack images of biofilm formed by wild type UPEC without (b, b’) and with MCSNP (c, c’), and ∆fimAΩkmr strains without (d, d’) and with MCSNP (e, e’). The samples were stained by fluorescein diacetate and propidium iodide before examination with confocal laser scanning microscopy. The biofilm thicknesses in b’–e’ were calculated to be 28, 6, 6, and 3.5 μM, respectively. (f) Schematic diagram showing the role of type I fimbriae in biofilm formation (top), inhibition of biofilm formation by MCSNPs (bottom), and failure of biofilm formation in the ∆fimA strains (middle).
Mentions: Since fimbriae are known to be main players in biofilm formation3132, we further characterized the phenotype of the ∆fimA strain by investigating its biofilm formation on polypropylene substrate using the crystal violet staining. The ∆fimA strain showed only 12.5% biofilm formation capacity compared to the wild type and complemented strains (Fig. 3a), confirming fimbriae have a primary role in UPEC biofilm formation as reported earlier in the other commensal E. coli strain31. Accordingly, we hypothesized that bacteria treated with MCSNPs show reduced biofilm formation capacity since MCSNP binding to fimbriae possibly blocks fimbriae-surface and fimbriae-fimbriae interactions, which are the key steps and prerequisites of biofilm formation. The fluorescein diacetate (FDA) and propidium iodide (PI) stained biofilms of wild type and ∆fimA UPEC without or with MCSNP were analyzed by confocal microscopy (Fig. 3b–e) and biofilm thickness was analyzed by z-stack image where one stack is equivalent to 1 μm (Fig. 3b’–e’). As expected, wild type UPEC produced the thickest biofilm, up to 28 μm, when MCSNP was absent (Fig. 3b–b’). However, treatment of MCSNP to the wild type UPEC reduced the biofilm thickness to 6 μm (Fig. 3c–c’), which was similar to that of ∆fimA strain (Fig. 3d–d’). The treatment of MCSNPs to the ∆fimA strain further reduced the biofilm thickness of ∆fimA strain to 3.5 μm (Fig. 3e–e’). These results suggest that MCSNP can also block biofilm formation mediated by other factors in addition to fimbriae. MCSNP treatment resulted in a 78.6% reduction in biofilm thickness of wild type UPEC. Significant reduction in biofilm thickness owing to the treatment with MCSNP is likely achieved due to the unavailability of free fimbriae required for the interaction with a surface for bacterial attachment. Taken together, these results indicate that the MCSNP-trapped wild type UPEC possesses the cell surface analogy with the ∆fimA strain by having fimbriae buried inside MCSNP. Accordingly, MCSNP can effectively block biofilm formation by inhibiting cell-cell interactions within the community. The schematic diagram showing biofilm formation by wild type UPEC and ∆fimA with and without MCSNP is depicted in Fig. 3f where the wild type strain formed a thicker biofilm and consequently creates a stronger physical barrier to drug entry than ∆fimA or MCSNP-complexed WT strain.

View Article: PubMed Central - PubMed

ABSTRACT

Antibiotic resistant bacteria not only affect human health and but also threatens the safety in hospitals and among communities. However, the emergence of drug resistant bacteria is inevitable due to evolutionary selection as a consequence of indiscriminate antibiotic usage. Therefore, it is necessary to develop a novel strategy by which pathogenic bacteria can be eliminated without triggering resistance. We propose a novel magnetic nanoparticle-based physical treatment against pathogenic bacteria, which blocks biofilm formation and kills bacteria. In this approach, multiple drug resistant Staphylococcus aureus USA300 and uropathogenic Escherichia coli CFT073 are trapped to the positively charged magnetic core-shell nanoparticles (MCSNPs) by electrostatic interaction. All the trapped bacteria can be completely killed within 30 min owing to the loss of membrane potential and dysfunction of membrane-associated complexes when exposed to the radiofrequency current. These results indicate that MCSNP-based physical treatment can be an alternative antibacterial strategy without leading to antibiotic resistance, and can be used for many purposes including environmental and therapeutic applications.

No MeSH data available.