Vancomycin-Dependent Response in Live Drug-Resistant Bacteria by Metabolic Labeling

Article abstract of DOI:10.1002/anie.201704851

The surge in drug-resistant bacterial infections threatens to overburden healthcare systems worldwide. Bacterial cell walls are essential to bacteria, thus making them unique targets for the development of antibiotics. We describe a cellular reporter to directly monitor the phenotypic switch in drug-resistant bacteria with temporal resolution. Vancomycin-resistant enterococci (VRE) escape the bactericidal action of vancomycin by chemically modifying their cell-wall precursors. A synthetic cell-wall analogue was developed to hijack the biosynthetic rewiring of drug-resistant cells in response to antibiotics. Our study provides the first in vivo VanX reporter agent that responds to cell-wall alteration in drug-resistant bacteria. Cellular reporters that reveal mechanisms related to antibiotic resistance can potentially have a significant impact on the fundamental understanding of cellular adaption to antibiotics.

Full text of DOI:10.1002/anie.201704851

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Vancomycin-dependent Response in Live Drug-Resistant
Bacteria via Metabolic Labeling
Authors: Marcos Moura Pires and Sean E. Pidgeon
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201704851
Angew. Chem. 10.1002/ange.201704851
Link to VoR: http://dx.doi.org/10.1002/anie.201704851
http://dx.doi.org/10.1002/ange.201704851

10.1002/anie.201704851
Angewandte Chemie International Edition
COMMUNICATION
Vancomycin-dependent Response in Live Drug-Resistant
Bacteria via Metabolic Labeling
Sean E. Pidgeon and Marcos M. Pires*
Abstract: The surge in drug-resistant bacterial infections threatens to
overburden healthcare systems worldwide. Bacterial cell walls are
essential to bacteria
– making them unique targets for the
development of antibiotics. We describe a cellular reporter to directly
monitor the phenotypic switch in drug resistant bacteria with temporal
resolution. Vancomycin-resistant Enterococci (VRE) escape the
bactericidal actions of vancomycin by chemically modifying their cell
wall precursors, which renders them drug insensitive. A synthetic cell
wall analog was developed to hijack the biosynthetic rewiring for drug
resistant cells in response to antibiotics. Our work provides the first in
vivo VanX reporter agent that responds to cell wall alteration in drug
resistant bacteria. Cellular reporters that reveal mechanisms related
to antibiotic resistance can potentially have a significant impact on the
fundamental understanding of cellular adaption to antibiotics.
Vancomycin, and related glycopeptides, disrupt PG assembly by
binding to the terminal D-alanyl-D-alanine (D-Ala-D-Ala) of Lipid II,
sequestering peptidoglycan (PG) building blocks (Figure 1a).[1]
The most prevalent form of vancomycin resistance occurs when
the last amino acid on Lipid II is chemically modified from D-
Alanine (D-Ala) to D-Lactic acid (D-Lac) (Figure 1b).[2] Metabolic
re-engineering of Lipid II in VRE cells is controlled by a set of
antibiotic inducible genes: vanR, vanS, vanH, vanA, and vanX
genes (vanRSHAX).[3] In order for VRE cells to reach high levels
of resistance they must vastly reduce the cytoplasmic pool of D-
Ala-D-Ala. To accomplish this, VRE cells express D,D-dipeptidase
VanX to hydrozyle D-Ala-D-Ala, which allows D-Ala-D-Lac to
accumulate in its place (Figure 1c).[4] We hypothesized that
synthetic analogs of D-Ala-D-Ala would enable the in vivo
interrogation of VanX activity, thus providing a platform for the first
direct phenotypic assay for VanX in VRE cells. Non-native
analogs of D-Ala-D-Ala were recently shown to be tolerated by
MurF.[5] Maurelli and co-workers applied this strategy to confirm
Figure 1. a) Schematic representation of the intracellular biosynthesis of PG
building blocks. Vancomycin sequestration of Lipid II molecules halts PG
polymerization. b) Structure of terminal end of Lipid II in drug-sensitive and -
resistant organisms with vancomycin. c) VanX-mediated hydrolysis of the
vancomycin susceptible D-Ala-D-Ala dipeptide building blocks.
absence of VanX activity, reporter dipeptides were expected to be
processed intracellularly, loaded onto Lipid II molecules, and
become imbedded within the mature PG. Once analogs are PG-
anchored, reporter fluorophores can be installed via copper-
catalyzed azide-alkyne cycloadditon (CuAAC) reactions (Figure
2c).[7] In cells displaying high levels of VanX activity, intracellular
hydrolysis of reporter dipeptides were expected to reduce the
dipeptide pool available for Lipid II production. VanX-mediated
hydrolysis of D-Ala-D-Ala generates the corresponding single
amino acids, which are not substrates for MurF, to drive the
utilization of D-Ala-D-Lac (Figure 2a). Elevated cellular levels of
VanX activity should result in attenuated levels of cell wall labeling,
affording access to the adaptation dynamics of live VRE cells.
the presence of PG in Chlamydia trachomatis – settling a 50 year
5d]
debate.[5a,
We anticipated that dipeptide analogs could be
leveraged to track the in vivo Lipid II processing associated with
vancomycin resistant bacteria (Figure 2a).
Previous reports had demonstrated VanX substrate plasticity
in accommodating non-native dipeptides in vitro.[6] As such, we
predicted that analogs of D-Ala-D-Ala containing reporter handles
could potentially be suitable substrates of VanX (Figure 2b). In the
We first evaluated two dipeptides, D-Ala-D-Pra and D-Pra-D-
Ala, both structural analogs of the endogenous VanX substrate
displaying an alkyne handle on the sidechain (Figure S1b).[5a, 5b]
A terminal alkyne was selected as the click chemistry partner due
to its small size. Adequate processing of D-Pra-D-Ala by VanXA
(the VanX in VanA-typed VRE cells) was anticipated
[*]
S. E. Pidgeon, Dr. M. M. Pires
Department of Chemistry, Lehigh University
6 E. Packer Ave., Bethlehem, PA 18015 (USA)
E-mail: map311@lehigh.edu
This article is protected by copyright. All rights reserved.

10.1002/anie.201704851
Angewandte Chemie International Edition
COMMUNICATION
the UDP-MurNAc-pentapeptide (the penultimate intermediate to
Lipid II) was isolated and characterized by LC-MS (Figure S3).
Based on these findings, it was evident that reporter dipeptides
entered the PG biosynthetic pathway.
The compatibility of D-Pra-D-Ala in metabolically labeling
diverse types of bacteria was also evaluated. Four additional
bacteria were chosen, namely Lactobacillus casei (L. casei),
Lactobacillus plantarum (L. plantarum), Enterococcus faecium (E.
faecium), and Enterococcus faecalis (E. faecalis). Interestingly,
both lactobacilli bacteria that naturally utilize the didepsipeptide D-
Ala-D-Lac were labeled to significant extents with the exogenous
dipeptide D-Pra-D-Ala (Figure S4). These findings indicate a lack
of tight selectivity by MurF on its substrate backbone (ester vs.
amide). Indeed, no dedicated MurF-like ligase exists in VRE that
joins D-Ala-D-Lac to form the UDP-MurNAc-pentadepsipeptide,
which highlights the substrate plasticity by MurF.[2a] Nonetheless,
this represents the first direct observation that MurF from
lactobacilli bacteria tolerate dipeptide substrates in live organisms.
Most importantly, treatment of two types of drug-sensitive
Enterococci bacteria with the reporter dipeptide led to high levels
of cellular labelling – a finding that set the stage for the potential
monitoring of VanX in live VRE cells.
We next focused on establishing the ability of exogenous D-
Pra-D-Ala to enter the PG biosynthetic pathway of VanA-type E.
faecium cells, which are extremely resistant to vancomycin and
part of the highly problematic ESKAPE class of pathogens.[10]
Similar to drug-sensitive E. faecium, significant cellular
fluorescence was observed in E. faecium BAA-2317 measured by
flow cytometry (Figure 2c). E. faecium (VanA) responds to
vancomycin exposure by depleting cytosolic D-Ala-D-Ala via
VanXA-mediated dipeptidase activity. Consistently, a 3.2-fold
decrease in cellular fluorescence was observed for E. faecium
(VanA) challenged with vancomycin, which could also be readily
visualized within 4 h of treatment (Figure S5). Labelling of the
same cells with the single amino acid D-Pra did not decrease in
the presence of vancomycin, an indication that the fluorescence
decrease in D-Pra-D-Ala labelled VRE cells is not linked to PG
transpeptidase activity (Figure S6). Accentuated labelling was
clearly visible at the septal ring, which is the primary site of Lipid
II pools (Figure 2d and Figure S7). In addition, PG digestion from
VRE cells by lysozyme was consistent with probe instalment
within the PG scaffold (Figure S8).
Figure 2. a) VanX dipeptidase activity hydrolyzes D-Ala-D-Ala and its analogs.
b) Proposed dipeptidase hydrolysis of synthetic analogs of D-Ala-D-Ala by VanX.
c) Analysis of E. faecium (VanA) treated overnight with 1 mM D-Pra-D-Ala (+/-
16 µg/mL vancomycin) followed by CuAAC with 6-FAM azide. Data are
represented as mean + SD (n = 3). P values were generated by an unpaired,
two-sided t-test using GraphPad Prism 5 and P values are indicated (*P≤0.05,
**P≤0.01, ***P≤0.001, ****P≤0.0001, and NS, not significant). d) Confocal
microscopy imaging of E. faecium (VanA) treated overnight with 1 mM D-Pra-D-
Ala followed by CuAAC with 6-FAM azide. Scale = 2 m.
based on our modeling of the VanXA active site using its crystal
structure information (Figure S2).[8] The alkyne handle on the
sidechain of D-Pra can be readily accommodated within the
VanXA binding pocket. Treatment of Bacillus subtilis (B. subtilis),
a model Gram-positive organism that can be readily cultured and
lacks pathogenicity cells, with D-Pra-D-Ala led to a ~ 100-fold
increase in cellular fluorescence compared to unlabeled cells,
suggestive of the metabolic utilization of this dipeptide probe
(Figure S1). A much smaller (~ 7-fold) increase was observed in
cells treated with the similar reporter dipeptide D-Ala-D-Pra. It was
anticipated that reduced cellular fluorescence might be attributed
to PG processing by surface-bound carboxypeptidases (including
DacA) during cell wall maturation.[9] Consistently, genetically
modified B. subtilis cells lacking dacA treated with D-Ala-D-Pra
displayed a nearly 10-fold increase in fluorescence levels,
consistent with DacA being partly responsible for signal reduction.
Despite the continuous supply and replenishment of reporter
dipeptides from the surrounding media, VanXA sufficiently
reduces the intracellular D-Pra-D-Ala concentration to significantly
reduce PG labeling in the presence of vancomycin.[6, 11] Titration
of E. faecium (VanA) cells with increasing concentrations of
vancomycin led to the corresponding attenuation of cellular
fluorescence (Figure S9). Moreover, vancomycin-dependent
fluorescence attenuation by vancomycin was observed in a wide
range of dipeptide probe concentrations (Figure S9). Crucially,
cellular fluorescence in drug-sensitive E. faecium remained
unchanged upon exposure to vancomycin (Figure S11). Next, a
series of control dipeptides were synthesized and examined in E.
faecium (VanA) cells. Three of the dipeptides were
stereochemical controls (2 diastereomers and 1 enantiomer) of D-
Pra-D-Ala (Figure 3b). Minimal cellular labelling was observed
with L-amino acid based dipeptides and dipeptide acetylation
Subsequently, we set out to confirm the entry of the reporter
dipeptides into the intracellular PG biosynthetic pathway. Cells
exposed to synthetic analogs of D-Ala-D-Ala are expected to
afford late stage (beyond the MurF ligation step) alkyne displaying
PG precursors in the bacterial cytosolic space. PG precursors
were harvested from cells treated with D-Pra-D-Ala. Subsequently,
This article is protected by copyright. All rights reserved.

10.1002/anie.201704851
Angewandte Chemie International Edition
COMMUNICATION
Figure 4. a) Chemical structure of vancomycin and two of its synthetic
derivatives. Flow cytometry analysis of E. faecium incubated overnight with D-
Pra-D-Ala (1 mM) and treated with the (b) vancomycin derivatives and (c) cell
wall antibiotics. Data are represented as mean + SD (n = 3). P values were
generated by an unpaired, two-sided t-test using GraphPad Prism 5 and P
values are indicated (*P≤0.05, **P≤0.01, ***P≤0.001, ****P≤0.0001, and NS, not
significant). c) Shading was internally normalized to represent the varying levels
of activation. The darker the blue shade, the lower cell labelling was observed.
ND = Not determined due to toxicity.
as expected, the expression of VanXA does not significantly alter
the pool of D-Ala-D-Lac in VRE. Moreover, they provide evidence
for the VanXA selectivity for dipeptides relative to didepsipeptide
in live VRE cells and illustrate the insight provided by synthetic
cell wall analogs in PG metabolism.
We next examined vancomycin resistance in VanB-type VRE
cells. More specifically, we set out to monitor VanXB activity in E.
faecalis organisms using D-Pra-D-Ala. Considerable cellular
labeling of E. faecalis ATCC 51299 (VanB) was observed at
similar levels to E. faecium (Figure S14). In contrast to VanA-
typed VRE, fluorescence signals remained unchanged when
challenged with increasing levels of vancomycin. These results
are suggestive of insufficient dipeptidase activity by VanXB in
reducing the intracellular pool of the reporter dipeptide.
Consistently, previous in vitro analysis of VanXB from E. faecalis
showed that it possesses ~ 10-fold lower specific activity relative
to E. faecium VanXA.[12] Moreover, unlike E. faecalis (VanB), E.
Figure 3. a) Flow cytometry analysis of E. faecium (VanA) incubated overnight
with dipeptide variants (1 mM). b) Schematic representation of the two phases
monitored with the VanX probe. Flow cytometry analysis of E. faecium (VanA)
VanX dipeptidase induction (c) and persistence (d) in response to vancomycin.
E. faecium cells were treated with D-Pra-D-Ala (1 mM) and collected at various
time points and fluorescently labeled with 6-FAM azide by CuAAC. Data are
represented as mean + SD (n = 3). e) VanX expression closes a futile cycle in
the production/degradation of D-Ala-D-Ala.
faecium
(VanA)
have
exclusively
UDP-MurNAc-
(NAc-D- Pra-D-Ala), which effectively renders the N-terminus
pentadepsipeptide PG precursors in the cytosolic space.
Together, our findings suggest that high VanXA activity is a
primary driver for the extreme levels of vancomycin-resistance
found in VanA-typed VRE.
amino group incompatible with MurF ligation.
We next evaluated the effect of the click chemistry reaction in
vancomycin-dependent cellular response in VRE cells. Two
additional dipeptides (D-Cys-D-Ala and D-Ala-D-Cys) were
synthesized and examined for their ability to enter the PG
biosynthetic pathway and report on VanXA activity (Figure S12).
VRE cells treated with D-Cys-D-Ala and D-Ala-D-Cys displayed
similar vancomycin-dependent labelling profiles. These results
suggest that the chemistry involved in the fluorophore tagging
step does not play a significant role. An additional dipeptide, D-
Pra-D-Lac, was also synthesized to assess in vivo VanXA
substrate specificity (Figure S13). The ester backbone found in D-
Pra-D-Lac should make it a poor substrate for VanXA, forming the
basis for the preferential accumulation of D-Ala-D-Lac over D-Ala-
D-Ala in the metabolic rewiring of induced VRE.[6] Treatment of E.
faecium (VanA) cells with D-Pra-D-Lac resulted in cellular labeling
that was independent of vancomycin. These results suggest that,
Having established a platform to monitor changes to cell wall
composition in VRE cells, we reasoned that our probe could be
leveraged to empirically determine the kinetics in cell wall
remodeling by determining the induction and persistence phases
(Figure 3c and d).[13] The induction phase reflects the kinetics in
cell wall alteration upon vancomycin exposure, whereas the
persistence phase reflects the kinetics in reverting back to D-Ala
based PG. VRE cells were exposed to vancomycin and collected
every 15 minutes to analyse for cellular fluorescence (Figure 3d).
Shortly after (45 minutes) vancomycin exposure, there was a
statistically significant difference in the cell wall composition and
this difference became more prominent over the next several
hours. Likewise, the persistence phase was relatively short-lived.
This article is protected by copyright. All rights reserved.

10.1002/anie.201704851
Angewandte Chemie International Edition
COMMUNICATION
Chem. Int. Ed. Engl. 2003, 42, 730-765; d) D. Kahne, C. Leimkuhler, W.
Lu, C. Walsh, Chem. Rev. 2005, 105, 425-448.
The rapid kinetics in induction and persistence point to a fitness
cost associated with maintaining D-Lac-based PG phenotype.[14]
Expression of VanXA closes a loop in the production and
degradation cycle of D-Ala-D-Ala (Figure 3f). In the process, VRE
exposed to vancomycin enter a futile cycle that is energetically
costly. Our results illustrate the ability of VRE cells to quickly
adapt to the presence of vancomycin by shifting the chemical
composition of their cell walls.
[3]
[4]
a) K. Koteva, H. J. Hong, X. D. Wang, I. Nazi, D. Hughes, M. J. Naldrett,
M. J. Buttner, G. D. Wright, Nat. Chem. Biol. 2010, 6, 327-329; b) S.
Evers, P. Courvalin, J. Bacteriol. 1996, 178, 1302-1309.
a) M. Arthur, F. Depardieu, H. A. Snaith, P. E. Reynolds, P. Courvalin,
Antimicrob. Agents Chemother. 1994, 38, 1899-1903; b) M. Arthur, F.
Depardieu, L. Cabanie, P. Reynolds, P. Courvalin, Mol. Microbiol. 1998,
30, 819-830; c) P. E. Reynolds, F. Depardieu, S. Dutka-Malen, M. Arthur,
P. Courvalin, Mol. Microbiol. 1994, 13, 1065-1070.
Finally, structural variants of vancomycin were evaluated for
resistance induction (Figure 4a). VRE cells assayed with aglycon-
vanc responded similarly to the parent vancomycin molecule
(Figure 4b).[15] On the other hand, desleucyl-vanc – a vancomycin
derivative missing the crucial leucine residue that participates in
the association to D-Ala-D-Ala on Lipid II molecules – showed
minimal decrease in labelling levels.[16] Next, we evaluated six
additional antibiotics encompassing a range of mechanisms of
action related to PG biosynthesis inactivation for their ability to
induce cell wall alteration in VRE cells (Figure 4c). From these
results, it is clear that teicoplanin is a more potent inducer than
vancomycin.[17] Interestingly, bacitracin showed strong induction
despite not having a proposed association with D-Ala-D-Ala,
contrary to previous reports using cell lysates.[18] On the other
hand, flavomycin treatment did not induce a signal change even
though it had been previously shown to induce gene expression
of the vanRSHAX cluster.[18] Notably, this assay should be
compatible with a high-throughput platform to analyse potential
drug leads for their ability to either inhibit induction or circumvent
sensing by VRE.
[5]
a) G. W. Liechti, E. Kuru, E. Hall, A. Kalinda, Y. V. Brun, M.
VanNieuwenhze, A. T. Maurelli, Nature 2014, 506, 507-510; b) S. Sarkar,
E. A. Libby, S. E. Pidgeon, J. Dworkin, M. M. Pires, Angew. Chem. Int.
Ed. Engl. 2016, 55, 8401-8404; c) J. M. Fura, S. E. Pidgeon, M.
Birabaharan, M. M. Pires, ACS Infect. Dis. 2016, 2, 302-309. d) G. Liechti,
E. Kuru, M. Packiam, Y. P. Hsu, S. Tekkam, E. Hall, J. T. Rittichier, M.
VanNieuwenhze, Y. V. Brun, A. T. Maurelli, PLoS Pathog. 2016, 12,
e1005590.
[6]
[7]
I. A. Lessard, S. D. Pratt, D. G. McCafferty, D. E. Bussiere, C. Hutchins,
B. L. Wanner, L. Katz, C. T. Walsh, Chemistry & Biology 1998, 5, 489-
504.
a) M. S. Siegrist, S. Whiteside, J. C. Jewett, A. Aditham, F. Cava, C. R.
Bertozzi, ACS Chem. Biol. 2013, 8, 500-505; b) J. T. Ngo, S. R. Adams,
T. J. Deerinck, D. Boassa, F. Rodriguez-Rivera, S. F. Palida, C. R.
Bertozzi, M. H. Ellisman, R. Y. Tsien, Nat. Chem. Biol. 2016, 12, 459-
465.
[8]
[9]
D. E. Bussiere, S. D. Pratt, L. Katz, J. M. Severin, T. Holzman, C. H. Park,
Mol. Cell. 1998, 2, 75-84.
a) C. W. Despreaux, R. F. Manning, Gene 1993, 131, 35-41; b) A. Atrih,
G. Bacher, G. Allmaier, M. P. Williamson, S. J. Foster, J. Bacteriol. 1999,
181, 3956-3966.
[10] H. W. Boucher, G. H. Talbot, J. S. Bradley, J. E. Edwards, D. Gilbert, L.
B. Rice, M. Scheld, B. Spellberg, J. Bartlett, Clin. Infect. Dis. 2009, 48, 1-
12.
Conclusions
[11] M. L. Matthews, G. Periyannan, C. Hajdin, T. K. Sidgel, B. Bennett, M.
W. Crowder, J. Am. Chem. Soc. 2006, 128, 13050-13051.
[12] C. M. Hill, K. M. Krause, S. R. Lewis, J. Blais, B. M. Benton, M. Mammen,
P. P. Humphrey, A. Kinana, J. W. Janc, Antimicrob. Agents Chemother.
2010, 54, 2814-2818.
In conclusion, a cell wall analog was developed to reveal
PG remodeling in drug resistant bacteria in response to
glycopeptide antibiotics. Our results showed that a simple cell wall
mimic can be a powerful tool to monitor the dynamic changes
upon induction of vancomycin-linked genes. We demonstrated
subtle differences in VanX activities in two different VRE types,
the selectivity of VanX between dipeptides and didepsipeptides in
live cells, and a new modality for tracking the induction of the drug
resistant phenotype in VRE.
[13] a) M. Baptista, P. Rodrigues, F. Depardieu, P. Courvalin, M. Arthur, Mol.
Microbiol. 1999, 32, 17-28; b) P. E. Reynolds, Cell Mol. Life Sci. 1998,
54, 325-331.
[14] M. L. Foucault, F. Depardieu, P. Courvalin, C. Grillot-Courvalin, Proc.
Natl. Acad. Sci. USA 2010, 107, 16964-16969.
[15] J. Kaplan, B. D. Korty, P. H. Axelsen, P. J. Loll, J. Med. Chem. 2001, 44,
1837-1840.
[16] R. C. Goldman, E. R. Baizman, C. B. Longley, A. A. Branstrom, FEMS
Microbiol. Lett. 2000, 183, 209-214.
Acknowledgements
[17] S. Dutka-Malen, R. Leclercq, V. Coutant, J. Duval, P. Courvalin,
Antimicrob. Agents Chemother. 1990, 34, 1875-1879.
[18] M. Baptista, F. Depardieu, P. Courvalin, M. Arthur, Antimicrob. Agents
Chemother. 1996, 40, 2291-2295.
This study was supported by Lehigh University (M.P.). We
would like to thank Dr. David Popham (Virginia Institute of
Technology) and Dr. Daniel Kearns (Indiana University) for the
kind gifts of B. subtilis and B. subtilis dacA strains.
Keywords: antibiotics • VanX • peptides • amino acids • drug
resistance
[1]
[2]
a) J. C. J. Barna, D. H. Williams, Annu. Rev. Microbiol. 1984, 38, 339-
357; C. Walsh, Nature 2000, 406, 775-781. b) T. L. Smith, M. L. Pearson,
K. R. Wilcox, C. Cruz, M. V. Lancaster, B. Robinson-Dunn, F. C. Tenover,
M. J. Zervos, J. D. Band, E. White, W. R. Jarvis, N. Engl. J. Med. 1999,
340, 493-501.
a) T. D. Bugg, G. D. Wright, S. Dutka-Malen, M. Arthur, P. Courvalin, C.
T. Walsh, Biochemistry 1991, 30, 10408-10415; b) M. Arthur, C. Molinas,
T. D. Bugg, G. D. Wright, C. T. Walsh, P. Courvalin, Antimicrob. Agents
Chemother. 1992, 36, 867-869; c) B. K. Hubbard, C. T. Walsh, Angew.
This article is protected by copyright. All rights reserved.

10.1002/anie.201704851
Angewandte Chemie International Edition
COMMUNICATION
COMMUNICATION
Vancomycin Resistance Probes:
Drug resistant bacteria pose a major
threat. Vancomycin Resistant
Enterococci express VanX
dipeptidases to remove drug-sensitive
building blocks. We disclose the first
series of compounds that
Sean E. Pidgeon and Marcos M. Pires*
Page No. – Page No.
Vancomycin-dependent Response
in Live Drug-Resistant Bacteria
via Metabolic Labeling
metabolically label bacterial cell walls
of live VRE cells to report on structural
alterations linked with antibiotic-
resistance.
This article is protected by copyright. All rights reserved.