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. 2015 Dec 28;21(1):E26.
doi: 10.3390/molecules21010026.

Strong and Nonspecific Synergistic Antibacterial Efficiency of Antibiotics Combined with Silver Nanoparticles at Very Low Concentrations Showing No Cytotoxic Effect

Aleš Panáček  1 , Monika Smékalová  2 , Martina Kilianová  3 , Robert Prucek  4 , Kateřina Bogdanová  5 , Renata Večeřová  6 , Milan Kolář  7 , Markéta Havrdová  8 , Grażyna Anna Płaza  9 , Joanna Chojniak  10 , Radek Zbořil  11 , Libor Kvítek  12
Affiliations

Strong and Nonspecific Synergistic Antibacterial Efficiency of Antibiotics Combined with Silver Nanoparticles at Very Low Concentrations Showing No Cytotoxic Effect

Aleš Panáček et al. Molecules. .

Abstract

The resistance of bacteria towards traditional antibiotics currently constitutes one of the most important health care issues with serious negative impacts in practice. Overcoming this issue can be achieved by using antibacterial agents with multimode antibacterial action. Silver nano-particles (AgNPs) are one of the well-known antibacterial substances showing such multimode antibacterial action. Therefore, AgNPs are suitable candidates for use in combinations with traditional antibiotics in order to improve their antibacterial action. In this work, a systematic study quantifying the synergistic effects of antibiotics with different modes of action and different chemical structures in combination with AgNPs against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus was performed. Employing the microdilution method as more suitable and reliable than the disc diffusion method, strong synergistic effects were shown for all tested antibiotics combined with AgNPs at very low concentrations of both antibiotics and AgNPs. No trends were observed for synergistic effects of antibiotics with different modes of action and different chemical structures in combination with AgNPs, indicating non-specific synergistic effects. Moreover, a very low amount of silver is needed for effective antibacterial action of the antibiotics, which represents an important finding for potential medical applications due to the negligible cytotoxic effect of AgNPs towards human cells at these concentration levels.

Keywords: antibacterial; antibiotics; cytotoxicity; resistant bacteria; silver nanoparticle; synergism.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Lognormal size distribution obtained from DLS measurements; (b) TEM image and (c) UV-Vis absorption spectra of AgNPs with diamater of 26 nm and narrow size distribution.
Figure 2
Figure 2
Viability of cells treated with antibiotics, silver NPs and their combinations using concentrations corresponding to the MIC value.
Figure 3
Figure 3
Viability of cells treated with antibiotics, silver NPs and their combinations using concentrations below the MIC value.
Figure 4
Figure 4
(a) UV-Vis absorption spectra of gelatin-stabilized (full line) and non-stabilized (dashed line) AgNPs dispersed in a culture medium at a ratio of 1:1; (b) TEM images of non-stabilized and (c) gelatin stabilized AgNPs.
See this image and copyright information in PMC

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