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Comparison of methods to detect the in vitro activity of silver nanoparticles (AgNP) against multidrug resistant bacteria.

Cavassin ED, de Figueiredo LF, Otoch JP, Seckler MM, de Oliveira RA, Franco FF, Marangoni VS, Zucolotto V, Levin AS, Costa SF - J Nanobiotechnology (2015)

Bottom Line: The activity of AgNPs using diffusion in solid media and the MIC methods showed similar effect against MDR and antimicrobial-susceptible isolates, with a higher effect against Gram-negative isolates.The activity of commercial silver nanoparticle and silver controls did not exceed the activity of the citrate and chitosan silver nanoparticles.The in vitro inhibitory effect was stronger against Gram-negative than Gram-positive, and similar against multidrug resistant and susceptible bacteria, with best result achieved using citrate and chitosan silver nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, University of São Paulo, São Paulo, Brazil. emerson_danguy@yahoo.com.br.

ABSTRACT

Background: Multidrug resistant microorganisms are a growing challenge and new substances that can be useful to treat infections due to these microorganisms are needed. Silver nanoparticle may be a future option for treatment of these infections, however, the methods described in vitro to evaluate the inhibitory effect are controversial.

Results: This study evaluated the in vitro activity of silver nanoparticles against 36 susceptible and 54 multidrug resistant Gram-positive and Gram-negative bacteria from clinical sources. The multidrug resistant bacteria were oxacilin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., carbapenem- and polymyxin B-resistant A. baumannii, carbapenem-resistant P. aeruginosa and carbapenem-resistant Enterobacteriaceae. We analyzed silver nanoparticles stabilized with citrate, chitosan and polyvinyl alcohol and commercial silver nanoparticle. Silver sulfadiazine and silver nitrate were used as control. Different methods were used: agar diffusion, minimum inhibitory concentration, minimum bactericidal concentration and time-kill. The activity of AgNPs using diffusion in solid media and the MIC methods showed similar effect against MDR and antimicrobial-susceptible isolates, with a higher effect against Gram-negative isolates. The better results were achieved with citrate and chitosan silver nanoparticle, both with MIC90 of 6.75 μg mL(-1), which can be due the lower stability of these particles and, consequently, release of Ag(+) ions as revealed by X-ray diffraction (XRD). The bactericidal effect was higher against antimicrobial-susceptible bacteria.

Conclusion: It seems that agar diffusion method can be used as screening test, minimum inhibitory concentration/minimum bactericidal concentration and time kill showed to be useful methods. The activity of commercial silver nanoparticle and silver controls did not exceed the activity of the citrate and chitosan silver nanoparticles. The in vitro inhibitory effect was stronger against Gram-negative than Gram-positive, and similar against multidrug resistant and susceptible bacteria, with best result achieved using citrate and chitosan silver nanoparticles. The bactericidal effect of silver nanoparticle may, in the future, be translated into important therapeutic and clinical options, especially considering the shortage of new antimicrobials against the emerging antimicrobial resistant microorganisms, in particular against Gram-negative bacteria.

No MeSH data available.


Related in: MedlinePlus

Distribution of size of inhibition zones (mm) obtained by diffusion in depth with AgNPs (citrate, chitosan and PVA) and controls against multidrug-resistant (MDR) (n = 54) and antimicrobial-susceptible bacteria (n = 36). Asterisk Only inhibition zones >6 mm were presented. All silver compounds showed absence of inhibition zones (<6 mm) when tested in MHA 5 % blood against the same microorganisms
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Fig5: Distribution of size of inhibition zones (mm) obtained by diffusion in depth with AgNPs (citrate, chitosan and PVA) and controls against multidrug-resistant (MDR) (n = 54) and antimicrobial-susceptible bacteria (n = 36). Asterisk Only inhibition zones >6 mm were presented. All silver compounds showed absence of inhibition zones (<6 mm) when tested in MHA 5 % blood against the same microorganisms

Mentions: All inhibition zones produced were plotted according to their size (Fig. 4). The inhibition zone was similar comparing MDR and susceptible bacteria, with larger zones for citrate and chitosan AgNPs than PVA AgNPs. Silver nitrate had no activity against MDR by this method (Fig. 5).Fig. 4


Comparison of methods to detect the in vitro activity of silver nanoparticles (AgNP) against multidrug resistant bacteria.

Cavassin ED, de Figueiredo LF, Otoch JP, Seckler MM, de Oliveira RA, Franco FF, Marangoni VS, Zucolotto V, Levin AS, Costa SF - J Nanobiotechnology (2015)

Distribution of size of inhibition zones (mm) obtained by diffusion in depth with AgNPs (citrate, chitosan and PVA) and controls against multidrug-resistant (MDR) (n = 54) and antimicrobial-susceptible bacteria (n = 36). Asterisk Only inhibition zones >6 mm were presented. All silver compounds showed absence of inhibition zones (<6 mm) when tested in MHA 5 % blood against the same microorganisms
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4593215&req=5

Fig5: Distribution of size of inhibition zones (mm) obtained by diffusion in depth with AgNPs (citrate, chitosan and PVA) and controls against multidrug-resistant (MDR) (n = 54) and antimicrobial-susceptible bacteria (n = 36). Asterisk Only inhibition zones >6 mm were presented. All silver compounds showed absence of inhibition zones (<6 mm) when tested in MHA 5 % blood against the same microorganisms
Mentions: All inhibition zones produced were plotted according to their size (Fig. 4). The inhibition zone was similar comparing MDR and susceptible bacteria, with larger zones for citrate and chitosan AgNPs than PVA AgNPs. Silver nitrate had no activity against MDR by this method (Fig. 5).Fig. 4

Bottom Line: The activity of AgNPs using diffusion in solid media and the MIC methods showed similar effect against MDR and antimicrobial-susceptible isolates, with a higher effect against Gram-negative isolates.The activity of commercial silver nanoparticle and silver controls did not exceed the activity of the citrate and chitosan silver nanoparticles.The in vitro inhibitory effect was stronger against Gram-negative than Gram-positive, and similar against multidrug resistant and susceptible bacteria, with best result achieved using citrate and chitosan silver nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: Department of Infectious Diseases, University of São Paulo, São Paulo, Brazil. emerson_danguy@yahoo.com.br.

ABSTRACT

Background: Multidrug resistant microorganisms are a growing challenge and new substances that can be useful to treat infections due to these microorganisms are needed. Silver nanoparticle may be a future option for treatment of these infections, however, the methods described in vitro to evaluate the inhibitory effect are controversial.

Results: This study evaluated the in vitro activity of silver nanoparticles against 36 susceptible and 54 multidrug resistant Gram-positive and Gram-negative bacteria from clinical sources. The multidrug resistant bacteria were oxacilin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., carbapenem- and polymyxin B-resistant A. baumannii, carbapenem-resistant P. aeruginosa and carbapenem-resistant Enterobacteriaceae. We analyzed silver nanoparticles stabilized with citrate, chitosan and polyvinyl alcohol and commercial silver nanoparticle. Silver sulfadiazine and silver nitrate were used as control. Different methods were used: agar diffusion, minimum inhibitory concentration, minimum bactericidal concentration and time-kill. The activity of AgNPs using diffusion in solid media and the MIC methods showed similar effect against MDR and antimicrobial-susceptible isolates, with a higher effect against Gram-negative isolates. The better results were achieved with citrate and chitosan silver nanoparticle, both with MIC90 of 6.75 μg mL(-1), which can be due the lower stability of these particles and, consequently, release of Ag(+) ions as revealed by X-ray diffraction (XRD). The bactericidal effect was higher against antimicrobial-susceptible bacteria.

Conclusion: It seems that agar diffusion method can be used as screening test, minimum inhibitory concentration/minimum bactericidal concentration and time kill showed to be useful methods. The activity of commercial silver nanoparticle and silver controls did not exceed the activity of the citrate and chitosan silver nanoparticles. The in vitro inhibitory effect was stronger against Gram-negative than Gram-positive, and similar against multidrug resistant and susceptible bacteria, with best result achieved using citrate and chitosan silver nanoparticles. The bactericidal effect of silver nanoparticle may, in the future, be translated into important therapeutic and clinical options, especially considering the shortage of new antimicrobials against the emerging antimicrobial resistant microorganisms, in particular against Gram-negative bacteria.

No MeSH data available.


Related in: MedlinePlus