AFM For Microbes Investigation And Antimicrobial Agent Evaluation

Ref ID: 19255

Author:

E. Dague, C. Formosa, M. Grare, R. Duval

Author address:

Laboratoire de Bactériologie Hygiène, Inst. Fédératif de Biologie, Toulouse, FRANCE, 3CNRS, UMR 7565, SRSMC, Nancy, FRANCE.

Full conference title:

53rd Interscience Conference on Antimicrobial Agents and Chemotherapy

Date: 10 September 2014

Abstract:

Background: Since 1986 and the description of Atomic Force Microscopy (AFM), living microbes were investigated at the nanoscale. The effects of antimicrobial agents have been evaluated at the single cell and molecule scale. AFM has been used to explore the nanoscale organization of A. fumigatus spores surface1, to get a better understanding of mycobacteria treatments or to evaluate new antimicrobials active against multi-resistant strains of P. aeruginosa. Methods: We used the Quantitative Imaging mode (Nanowizard III: JPK instrument Berlin, Germany) to image and quantify C. albicans adhesive properties5. In this mode, force curves are recorded at high speed. This gives access, to the sample topography, elasticity, and adhesive properties. We used MLCT cantilevers (Bruker probes) with a nominal spring constant of 0.01 N.m-1. Experiments were made in acetate buffer pH 5.5.The chitin levels were determined by Reissig method after an enzymatic hydroloysis of the cell walls. Results: In this study we focused on the fungus C. albicans and the nanoscale effect of caspofungin. We show that the cell morphology is not affected by caspofungin even at high doses (4xMIC). On the contrary the adhesive and nanomechanical properties are completely different on native cells, cells treated by 0.5xMIC and 4xMIC. First the elasticity is increased with the increasing caspofungin dose. This correlates with the chitin rate in the cell wall. Second, native cells present adhesive nanodomains especially on
daughter cells. At 0.5xMIC all the cell is highly adhesive except the budscares. Finally, at 4x MIC, the cells are no more adhesive. We hypothetize that this adhesive pattern is due to the protein Als 1 which is known to be over expressed when cells are exposed to subletal doses of caspofungin. Conclusions:AFM is useful in microbiology and provide the unique opportunity to explore living microbes at the nansocale. AFM is also interesting to investigate the nanoscale effects of antimicrobial agents.References: 1. Dague E et al. Nano Lett 7 3026 2007 2. Alsteens D et al. Pflugers Arch – Eur J Physiol 456 117 2008 3. Formosa C el al. Nanomedicine Nanotechnol. Biol. Med. 8 12 2012 4. Formosa C et al. Sci. Reports 2 2012 5. Chopinet L et al. Micron 48 26 2013

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Conference Year: 2013

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