Nanoscale effects of antibiotics on P. aeruginosa
Cecile Formosa, MS
, Marion Grare, PhD
, Raphaël E. Duval, PhD
Etienne Dague, PhD
Centre National de la Recherche Scientifique, Laboratoire d'Analyse et d'Architecture des Systèmes (LAAS), Toulouse, France
Centre National de la Recherche Scientifique, Toulouse, France
Université de Toulouse, Toulouse, France
SRSMC, Nancy-University, CNRS, Faculty of Pharmacy, Nancy, France
Laboratoire de Bactériologie Hygiène, Institut Fédératif de Biologie, Toulouse, France
Received 28 June 2011; accepted 20 September 2011
Studying living bacteria at the nanoscale in their native liquid environment opens an unexplored landscape. We focus on Pseudomonas
aeruginosa and demonstrate how the cell wall is biophysically affected at the nanoscale by two reference antibiotics (ticarcillin and
tobramycin). The elasticity of the cells drops dramatically after treatment (from 263 ± 70 kPa to 50 ± 18 and 24 ± 4 kPa, respectively on
ticarcillin- and tobramycin-treated bacteria) and major micro- and nano-morphological modifications are observed (the surface roughness of
native, ticarcillin- and tobramycin-treated bacteria are respectively 2.5, 0.8, and 4.4 nm for a surface area of 40,000 nm²). Thus the nanoscale
approach in liquid is valid and can be extended.
From the Clinical Editor: Pseudomonas aeruginosa cell wall was demonstrated to be biophysically affected at the nanoscale by two
reference antibiotics, ticarcillin, and tobramycin, with the elasticity dropping dramatically after treatment.
© 2012 Elsevier Inc. All rights reserved.
Key words: Pseudomonas aeruginosa; Atomic Force Microscopy; Ticarcillin; Tobramycin; Elasticity; Bacterial cell wall
For 25 years, Atomic Force Microscopy (AFM) has emerged
as a valuable tool in microbiology.
Recently it has been used
to study the effects of antimicrobial drugs on living micro-
An advantage of AFM is the possibility to work in
liquid on living cells. Nevertheless, sample immobilization is a
and explains why in most publications the bacteria
were air dried. Here, we focused on the dreadful bacteria
and overcome the immobilization
problem by taking advantage of electrostatic interactions
between a positively charged surface and the negatively charged
bacteria. P. aeruginosa, is implicated in 10% of nosocomial
infections in France. This pathogen, resistant to several anti-
biotics and antiseptics, has a great capacity for acquiring new
resistance mechanisms under selective antibiotic pressure.
Therefore, understanding the effects of antibiotics on these
bacteria has become a necessity. We studied two reference
antibiotics, ticarcillin and tobramycin, which are highly active
on P. aeruginosa. They have known action mechanisms and are
widely used in terapeutics, unlike other molecules, e.g. colistin
wihch effects were recently studied.
Ticarcillin is a β-lactamin
which inhibits the bacterial transpeptidases and transglyco-
sylases responsible for the assembly of the cell wall pep-
Tobramycin is an aminoglycoside that works by
binding to the 30S and 50S bacterial ribosome to prevent
formation of the 70S complex. As a result, mRNA cannot
be translated into protein.
These two different mechanisms
of action should therefore produce different effects on the
bacterial cells. In this study, our purpose was to understand
better the antibiotics' effects on the cell wall of P. aeruginosa
at the nanoscale.
We chose to explore the effects of tobramycin and ticarcillin
on P. aeruginosa ATCC 27853. We used AFM (details appear in
Supplementary Material 1) to explore bacterial cell wall
modifications. We recorded images of single bacteria (Figure 1)
and images at higher resolution on the top of the cells to
qualitatively explore the impact of tobramycin and ticarcillin on
Nanomedicine: Nanotechnology, Biology, and Medicine
8 (2012) 12 – 16
Financial support (for Marion Grare, Raphaël E. Duval) was provided by
the French Ministry of Further Education and Research and the French National
Scientific Research Center (CNRS). Etienne Dague is a researcher from LAAS-
CNRS UPR 8001, Centre National de la Recherche Scientifique, hosted in
Centre Pierre Potier ITAV, UMS 3039. Cecile Formosa is funded by LAAS-
CNRS UPR 8001, hosted in Centre Pierre Potier ITAV, UMS 3039.
No conflict of interest was reported by the authors of this article.
Corresponding author: LAAS-CNRS, Groupe NBS, 31000 Toulouse, France.
E-mail address: firstname.lastname@example.org (E. Dague).
1549-9634/$ – see front matter © 2012 Elsevier Inc. All rights reserved.
Please cite this article as: C. Formosa, M. Grare, R.E. Duval, E. Dague, Nanoscale effects of antibiotics on P. aeruginosa. Nanomedicine: NBM