J Antimicrob Chemother 2014; 69: 1777 – 1784
doi:10.1093/jac/dku084 Advance Access publication 25 April 2014
NDM carbapenemases in the United Kingdom: an analysis
of the first 250 cases
Anu Jain1, Katie L Hopkins1, Jane Turton1, Michel Doumith1, Robert Hill1, Richard Loy1,
Daniele Meunier1, Rachel Pike1, David M. Livermore1,2 and Neil Woodford1*
1
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, Public Health England, London NW9 5EQ, UK;
2
Norwich Medical School, University of East Anglia, Norwich NR4 7TJ, UK
*Corresponding author. AMRHAI, PHE Reference Microbiology Services, 61 Colindale Avenue, London, NW9 5EQ, UK.
Tel: +44 (0)20 8327 7255; E-mail: [email protected]
Received 11 December 2013; returned 28 January 2014; revised 4 March 2014; accepted 6 March 2014
Objectives: Gram-negative bacteria with diverse carbapenemases, including New Delhi metallo-b-lactamase
(NDM) enzymes, have been increasingly recorded in the UK since 2007. We analysed patient data for NDM-positive isolates confirmed by the national reference laboratory from UK laboratories from February 2008 to July
2013.
Methods: Isolates resistant to carbapenems and with imipenem MICs reduced ≥8-fold by EDTA were tested by
PCR for genes encoding acquired class B carbapenemases. MICs were determined by BSAC agar dilution methodology. When requested by the sender, or when they were members of apparent clusters, NDM-positive isolates
were typed by variable number tandem repeat (VNTR) analysis or PFGE. Data provided by the sending laboratories
were collated and reviewed.
Results: From February 2008 to July 2013 the reference laboratory confirmed 326 NDM-positive isolates from 250
patients, submitted by 83 laboratories. Most (85%, 213/250) patients were already hospitalized when the NDMpositive bacteria were detected, were male (61%, 152/250) and were aged .60 years (58%, 145/250). Travel
history was available for only 40% of patients, but 52% (53/101) of these had documented healthcare contact
within or travel to the Indian subcontinent. Most NDM-positive isolates (94%, 306/326) were Enterobacteriaceae
with just 6% (20/326) non-fermenters; the predominant hosts were Klebsiella spp. (55%, 180/326) and
Escherichia coli (25%, 80/326). Almost all NDM-positive isolates were resistant to multiple antibiotic classes,
but 90% remained susceptible to colistin.
Conclusions: Gram-negative bacteria with NDM carbapenemases are a growing challenge, especially for elderly
hospitalized patients, including those with healthcare contact in the Indian subcontinent, and leave few therapeutic options. UK outbreaks remain rare and contained.
Keywords: MBLs, meropenem, Enterobacteriaceae, Pseudomonas, Acinetobacter
Introduction
Increasing antimicrobial resistance has recently been highlighted
both nationally in the Chief Medical Officer for England’s annual
report1 and internationally.2,3 Gram-negative bacteria carrying
carbapenem-inactivating b-lactamases (carbapenemases) are
an especial concern given that, until recently, carbapenems
were the ‘reserve’ antibiotics for infections caused by bacteria
already resistant to other agents. Acquired carbapenemases are
produced by increasing numbers of Enterobacteriaceae (mostly
Klebsiella spp.) and non-fermenters. They include metallo- (e.g.
IMP, NDM, VIM) and non-metallo- (e.g. KPC, OXA-48) b-lactamases.
New Delhi metallo-b-lactamases (NDMs) were first reported in
20094 and subsequently have been increasingly reported from
across the world, often, though not always, in bacteria from
patients with epidemiological links (healthcare contact and/or travel) to the Indian subcontinent or the Balkans region.5 – 8
Metallo-b-lactamases (MBLs), including NDM enzymes, are
inhibited by metal ion chelators such as EDTA. They hydrolyse and
confer resistance to carbapenems and other b-lactam antibiotics,
except aztreonam.9 NDM-producing bacteria are also often resistant to fluoroquinolones, aminoglycosides and, owing to production
of extended-spectrum b-lactamases (ESBLs) or AmpC enzymes,
also to aztreonam.10 Therapeutic options consequently are
extremely limited, with isolates often susceptible only to colistin,
and more variably, tigecycline, fosfomycin and nitrofurantoin.10,11
# Crown copyright 2014.
1777
Jain et al.
Since the first reports of NDM-type enzymes,4,10 the UK
has seen more affected patients than most other countries in
Western Europe.6 Here we review the first 250 UK cases recognized as infected or colonized by bacteria producing NDM-type
enzymes, as ascertained by the Antimicrobial Resistance and
Healthcare Associated Infections (AMRHAI) Reference Unit of
Public Health England (PHE).
Materials and methods
Bacterial isolates, identification and susceptibility testing
Known patients
New patients
Laboratories
35
30
25
20
15
10
5
0
2008 Q1
2008 Q2
2008 Q3
2008 Q4
2009 Q1
2009 Q2
2009 Q3
2009 Q4
2010 Q1
2010 Q2
2010 Q3
2010 Q4
2011 Q1
2011 Q2
2011 Q3
2011 Q4
2012 Q1
2012 Q2
2012 Q3
2012 Q4
2013 Q1
2013 Q2
Number of patients/ laboratories
40
Isolates had been submitted to PHE’s national reference laboratory,
AMRHAI, from laboratories across the UK between February 2008 and
July 2013 for investigation of resistance that was considered ‘unusual’
by the referring laboratories, including resistance to carbapenems.
Bacterial identification was confirmed in AMRHAI using chromogenic
agars [CHROMagarTM Orientation (CHROMagar, Paris, France) and
Brilliance UTI (Oxoid, Basingstoke, UK)], API-20E tests (bioMérieux SA,
Marcy-l’Étoile, France) or, since August 2012, by matrix-assisted laser
desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS;
Bruker Microflex LT, Bruker Daltonik GmbH, Bremen, Germany). In addition,
in-house algorithms were used where required to identify unusual organisms by housekeeping gene sequence cluster analysis.
Antibiotic susceptibilities (MICs) were determined by BSAC agar dilution12 using AMRHAI’s standard Gram-negative antibiotic panel, which
included ertapenem, imipenem (tested with/without EDTA at 320 mg/L
to detect likely MBL producers) and meropenem. MICs were interpreted
using BSAC breakpoints, where available.13
Year and quarter
Figure 1. Numbers of new and known affected patients and laboratories
sending NDM-positive isolates per quarter during the study period. Three
new patients were recorded in July 2013 and are not included in the figure.
Screening for metallo-carbapenemase genes
Isolates resistant to one or more carbapenems and exhibiting a significant
(≥8-fold) reduction in imipenem MIC in the presence of EDTA were tested
Table 1. Source and species for the NDM-positive isolates from different settings
Hospital setting
Species
Klebsiella spp.
E. coli
Enterobacter spp.
Citrobacter spp.
Providencia spp.
Morganella spp.
Serratia spp.
Acinetobacter spp.
P. aeruginosa
Total
urines
clinical or
screening swabs
blood cultures and
line tips
respiratory
tissue
and fluid
faeces
not
known
GP
urines
Total
64
25
6
5
2
0
0
0
3
47
15
9
2
1
0
0
13
1
17
10
4
0
0
0
0
1
0
18
2
5
1
0
1
1
1
0
8
3
2
0
0
0
0
1
0
2
2
3
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
18
22
2
0
0
0
0
0
0
175
79
31
9
3
1
1
16
4
105
88
32
29
14
8
1
42
319
Unknown setting
urines
clinical or
screening swabs
blood cultures and
line tips
respiratory
tissue
and fluid
faeces
not
known
Klebsiella spp.
E. coli
Serratia spp.
3
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
—
—
—
5
1
1
Total
5
1
0
0
0
0
1
—
7
GP, general practice.
Data are numbers of isolates.
1778
JAC
NDM carbapenemases in the UK
by in-house PCR assays for genes encoding acquired class B (IMP, VIM,
NDM, GIM, SIM and SPM) carbapenemases as previously described,14,15
and/or with a commercial microarray (Check-MDR CT102; Check-Points,
Wageningen, The Netherlands).16
Typing
Where requested by the sending laboratories, isolates of Klebsiella pneumoniae were typed by variable number tandem repeat (VNTR) analysis of
nine loci (A, E, H, J, K, D17 and N1, N2 and N418). Sequence types (STs) of
representatives of the most frequently found VNTR types were determined
by multilocus sequence typing (MLST).19 Pseudomonas aeruginosa isolates
were typed by VNTR analysis of nine loci, as described previously20 and STs
were determined using the scheme of Curran et al.21
For other species, typing was carried out by PFGE of XbaI-digested
(Escherichia coli, Enterobacter spp., Citrobacter spp.) or ApaI-digested
(Acinetobacter spp.) genomic DNA, as described previously;17 pre-2010
isolates of K. pneumoniae were also typed by this method. VNTR profiles
or gel images were analysed and compared using BioNumerics (Applied
Maths, Sint-Martens-Latem, Belgium) software, version 6.1. Isolates sharing highly similar banding patterns (with a similarity of ≥86%) by PFGE
were described as clusters, irrespective of whether or not there were epidemiological links between the source patients. MLST of E. coli cluster 1
was carried out as described by Wirth et al.22
Patient demographic information
Data for patients yielding NDM-positive isolates were collated and
reviewed using information provided by the referring laboratory on the
request forms that accompanied submissions. Depending on where the
sample was taken, patients were categorized as either in a hospital setting
or in a general practice setting. For the purpose of this analysis, a patient
was categorized as ‘new’ if found to have NDM-positive isolates detected
by AMRHAI for the first time and ‘known’ if the patient was known to
AMRHAI as having previously yielded an NDM-positive isolate. Treatment
regimens and outcome data were not available for analysis.
Data analysis
Data were analysed using Microsoft Excel and Access.
Results
Demographics of patients affected and distribution
During the study period, AMRHAI confirmed 326 NDM-positive isolates, submitted by 83 UK laboratories from 250 patients. The isolates from 2008 were identified retrospectively after the initial
characterization of the blaNDM gene and later isolates were
Table 2. MIC distributions for Enterobacteriaceaea (n¼306) and non-fermentersb (n ¼20) producing NDM carbapenemase
Antibiotic
(range tested, mg/L)
Ertapenem (0.125– 16)
Imipenem (0.06– 128)
Meropenem (0.06– 32)
Amikacin (0.5–64)
Gentamicin (0.125–32)
Tobramycin (0.125– 32)
Ciprofloxacin (0.125–8)
Isolates
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Enterobacteriaceae
non-fermenters
Colistin (0.5 –32)
Enterobacteriaceae
non-fermenters
Tigecycline (0.25–16)
Enterobacteriaceae
non-fermenters
BSAC
breakpoint(s)13
≤S/.R
≤0.5/.1
NT
≤2/.8
Ac≤2/.8
Ps≤4/.8
≤2/.8
≤2/.8
≤8/.16
≤8/.16
≤2/.4
≤4/.4
≤2/.4
Ac≤4/.4d
Ps≤4/.4
≤0.5/.1
Ac≤1/.1
Ps≤0.5/.1
≤2/.2
Ac≤2/.2
Ps≤4/.4
≤1/.2
Ac≤0.25/.0.5d,f
Number of isolates with MIC (mg/L)
≤0.125
0.25
0.5
1
1
1
15
1
10
1
2
4
8
16
32
1
1
2
10
290c
3
5
22
64
118
1
66
4
1
5
9
92
10
35
1
15
2
1
9
2
1
1
19
4
164c
18c
1
3
262c
14c
238c
10c
7
1
243c
15c
19
1
14
17
1
2
19
1
8
3
2
1
1
18
1
14
1
49e
3e
5
1
4
8
7
171e
11e
98
7
7
1
1
7
4
74
2
61
2
68
3
34
3
10
1
3
6
1
9
1
17
1
3
64
≥128
NA
2
7c
27
14
1
1
0
NT
1
0
1
0.3
0
22
15
10
10
7
10
1
12
15
8
1
90
95
7
6
60
15
1
218
12
%S
1
1
S, susceptible; R, resistant; NA, not available; NT, not tested; Ac, Acinetobacter spp.; Ps, Pseudomonas spp.
Cells highlighted in dark grey are resistant isolates; those in light grey are intermediate; and white are susceptible.
a
180 Klebsiella spp., 80 E. coli, 31 Enterobacter spp., 9 Citrobacter spp., 3 Providencia spp., 1 M. morganii and 2 Serratia marcescens.
b
4 P. aeruginosa and 16 Acinetobacter spp.
c
MIC greater than or equal to the value shown.
d
EUCAST breakpoint.29
e
MIC less than or equal to indicated value.
f
Non-species-related breakpoint.29
1779
Jain et al.
Hospital
3
3
3
3
3
3
3
3
3
3
3
3
3
7
4
4
4
4
4
4
4
7
6
6
6
5
5
3
2
3
7
5
5
5
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
6
6
6
6
6
6
6
6
6
5
5
5
5
4
5
5
5
5
5
5
5
5
50
1780
5
5
5
5
5
5
5
5
5
5
5
5
5
3
5
5
5
5
5
5
4
5
3
3
3
3
3
1
2
2
2
2
2
2
2
2
2
2
2
2
2
5
3
3
3
3
3
3
4
3
6
6
6
6
6
5
4
3
5
5
7
5
6
6
6
6
6
6
6
6
6
6
6
6
6
6
8
4
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
4
4
5
2
3
3
3
3
3
3
3
3
3
6
1
4
2
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
6
3
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
1
1
1
1
1
5
5
5
5
5
5
5
5
6
13
13
13
13
13
13
13
13
13
13
13
13
13
14
5
5
5
5
5
5
4
5
4
4
4
4
4
2
4
7
5
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
2
14
14
14
14
14
14
14
14
5
2
2
2
2
2
2
2
2
2
2
2
2
2
6
2
2
2
2
2
2
1
1
0
1
2
1
2
0
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
14
14
14
14
14
14
14
14
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
1
2
2
2
2
2
2
3
3
2
2
2
2
3
4
4
4
1
1
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
1
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
2
4
4
4
4
4
4
4
4
1
N4
N2
N1
D
K
J
H
E
A
30
25
20
15
10
5
0
Euclidian
distance
3
3
4
4
4
4
4
4
4
4
4
4
4
2
3
3
3
3
3
3
2
3
2
2
2
2
2
3
2
5
1
3
3
4
3
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
4
4
3
3
2
2
2
2
2
2
2
2
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Date
week/year
W
R
AG
M
J
I
O
O
O
C
Q
V
AB
K
K
AA
AE
AF
AF
M
AA
AC
AF
AF
M
E
M
P
T
U
Z
M
G
B
H
X
X
X
X
X
X
X
X
X
X
X
X
F
Q
N
Y
R
R
R
U
U
R
R
R
R
A
D
6/2012
49/2012
32/2011
15/2012
36/2012
37/2012
38/2012
51/2012
8/2013
11/2013
23/2013
25/2013
25/2013
7/2012
45/2012
51/2012
8/2013
21/2013
22/2013
26/2013
9/2011
22/2013
31/2012
33/2012
26/2013
37/2011
15/2013
48/2012
26/2013
39/2011
30/2012
8/2012
11/2013
4/2012
24/2013
5/2010
29/2010
29/2010
29/2010
30/2010
30/2010
31/2010
34/2010
34/2010
39/2010
39/2010
40/2010
41/2012
44/2012
12/2013
16/2013
4/2012
10/2012
12/2012
28/2012
31/2012
42/2012
51/2012
18/2013
21/2013
26/2013
30/2013
NDM
OXA-48 and NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
O
O
V
R
AA
AA
AD
AA
AC
AA
J
S
AA
E
AH
K
E
L
Q
F
R
F
K
10/2010
14/2010
13/2011
18/2012
33/2012
34/2012
07/2013
9/2013
22/2013
28/2011
36/2012
47/2012
09/2012
1/2011
19/2011
45/2012
47/2012
25/2012
16/2013
18/2013
21/2013
25/2013
5/2011
NDM
NDM
NDM
NDM
NDM
NDM
OXA-48 and NDM
NDM
NDM
NDM
OXA-48 and NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
NDM
ST11
ST17
Cluster C
Cluster A
ST15
ST14
ST101
Cluster B
JAC
NDM carbapenemases in the UK
identified within 1 – 2 weeks of submission.4 The first known UK
isolate with NDM carbapenemase in 2008 was an E. coli isolate
from a rectal swab specimen taken from a 26-year-old hospitalized
female patient who had a history of travel to India. The number of
new patients affected (i.e. infected or colonized) increased
year-on-year: 7 in 2008, 29 in 2009, 31 in 2010, 46 in 2011, 74 in
2012 and 63 in the first 7 months of 2013.
The regional distribution of affected patients from February 2008
to July 2013 was as follows: England (n ¼ 233), Scotland (n¼ 7),
Wales (n¼4) and Northern Ireland (n¼6); no region was spared.
The largest number of patients was from London (n¼88), followed
by the West Midlands (n ¼ 39), Greater Manchester (n ¼ 23) and
Yorkshire and Humber (n¼21). Figure 1 shows the numbers of referring laboratories and patients per quarter during the study period
and the proportions of new and known patients with NDM-positive
bacteria, illustrating the ongoing rise in these numbers.
The majority (82%, 205/250) of the source patients were hospitalized, but 12% (30/250) were from primary care, 3% (8/250)
had isolates taken from both these settings and the setting for
3% (7/250) of patients was unavailable. Most isolates (58%,
145/250) were from patients aged .60 years and the majority
of source patients (61%, 152/250) were male. Patients in primary
care were likewise mainly male (58%, 22/38), and 86% (19/22) of
these male patients were .60 years of age.
Rudimentary travel history was available for only 40% (101/
250) of the patients. Among this subgroup, 52% (53/101) had
documented healthcare contact within or travel to the Indian
subcontinent. Seven percent (7/101) had a history of travel to
other countries, including Spain, Uganda, Kuwait, Egypt and the
Democratic Republic of Congo; the country of travel was unavailable for two patients who nevertheless were reported to have
travelled; 41% (41/101) of patients with data available were stated to have no history of travel.
Single NDM-positive isolates were received from 80% (201/
250) of the patients and multiple isolates from the remaining
20% (49 patients). Amongst these latter patients with multiple
NDM-positive isolates, 29% (14/49) had NDM-positive organisms
of different species or genera. NDM-positive isolates were referred
over periods of .6 months in 14% of patients (7/49) and for
.1 year in two patients, but many patients had no follow-up isolates, precluding assessment of carriage duration. NDM-positive
isolates were obtained from more than one anatomical site in
37% patients (18/49).
The date when the sample was taken was available for 87%
(284/326) of isolates and the median duration between this
date and the isolate being received at AMRHAI was 8 days (IQR
6 –11 days).
Microbiology
The majority (94%, 306/326) of the NDM-positive isolates were
Enterobacteriaceae, but 6% (20 isolates) were non-fermenters.
Table 1 illustrates the details of source and species for the
NDM-positive isolates for various settings. The commonest
Enterobacteriaceae hosts were Klebsiella spp. (59%, 180/306) followed by E. coli (26%, 80/306). Acinetobacter spp. were the commonest non-fermenter hosts (80%, 16 isolates).
Most isolates (85%, 277/326) were from samples taken in hospital, but 13% (42/326) were from general practice urines; the
setting was unavailable for 2% (7/326) of isolates. Thirty-eight
percent of isolates from hospital settings were from urine specimens, with swabs contributing a further 32%. These swabs
were divided fairly evenly between those from clinical sites and
those taken for screening (49% versus 51%). Thirty-two (9.8%)
of isolates were from blood cultures or line tips (Table 1).
Antibiotic susceptibility
MIC distributions for the Enterobacteriaceae and non-fermenters
with NDM carbapenemases are shown in Table 2. Most NDMpositive bacteria were resistant or non-susceptible to all three carbapenems tested. However, two K. pneumoniae isolates and one
Citrobacter koseri isolate were susceptible to imipenem, but with
synergy still observed between this agent and EDTA. One isolate of
Morganella morganii was susceptible to meropenem but resistant
to both imipenem and ertapenem. Aztreonam susceptibilities
were available for 67% (220/326) isolates, and only 12% (24/
206) of the Enterobacteriaceae isolates tested were susceptible.
Resistance to all three aminoglycosides routinely tested (amikacin, gentamicin and tobramycin) was seen in 76% (234/306) of
NDM-positive Enterobacteriaceae, but 18% were susceptible to
at least one aminoglycoside and 6% to all three. High-level resistance (amikacin MICs .64 mg/L and gentamicin and tobramycin
MICs .32 mg/L) was observed for 218 Enterobacteriaceae isolates.
Similarly, 70% (14/20) of NDM-positive non-fermenters were resistant to the three aminoglycosides and 10 showed high-level
resistance.
Most isolates were susceptible to colistin (90% of Enterobacteriaceae and 95% of non-fermenters). Susceptibility to ciprofloxacin
varied from 12% to 15% according to species (Table 2).
Typing of the isolates
One hundred and seven out of 168 isolates of K. pneumoniae with
NDM enzymes were typed by VNTR. After excluding isolates belonging to the same strain from a single patient, 85 results remained for
analysis. In addition, a further 30 K. pneumoniae had been typed by
PFGE. Most NDM-positive K. pneumoniae isolates represented either
sporadic strains (27 unique types identified in total) or belonged to
well-recognized international lineages (STs 11, 14, 15 and 17),
which are prevalent generally and have been associated previously
with other acquired carbapenemase genes (blaKPC, blaVIM or
blaOXA-48). Isolates belonging to these lineages (which may have
acquired blaNDM repeatedly and separately) were received from
multiple requestors with no epidemiological links apparent
between many cases (Figure 2). The seven NDM-positive ST15 isolates from patients from a single hospital (Figure 2, ST15 cluster,
hospital R) were received over a 17 month period, with no obvious
Figure 2. Dendrogram of VNTR profiles of NDM-positive isolates of K. pneumoniae from 85 patients received between January 2010 and the end of the
study period from 34 hospitals (A– Z and AA–AH). Three isolates were also PCR-positive for genes encoding an OXA-48-like carbapenemase. Isolates
marked with circles were from an outbreak in hospital X; isolates marked with squares are of ST15 from a single hospital (R). There was an
epidemiological link between ST15 isolates from hospital U (marked with diamonds) and hospital R. A score of 50 repeat units is used for very large
amplicons, indicative of an insertion sequence (isolate from hospital K). Blank entries represent no amplification at that locus for that isolate.
1781
Jain et al.
clustering in time. Nevertheless, there was an outbreak involving 14
patients in a urology clinic in 2010 (Figure 2, cluster A, hospital X;
two additional isolates not shown in the figure were typed by
PFGE). There were some other instances of epidemiologically linked
cases, where cross-infection was likely, as noted previously.10 One
patient was found to have two distinct K. pneumoniae strains each
carrying blaNDM.
Typing data (PFGE) were also available for 37 non-duplicate
E. coli isolates. Most (65%, 24/37) were unique, but three clusters
were identified, one of which consisted of isolates from eight
patients from six different, geographically distant hospitals
(Figure 3). This cluster corresponds to ST636. Two other pairs of
isolates shared similar PFGE profiles, but in each case they were
separated in both time and space.
For the remaining genera, only limited numbers of isolates
were typed. While there were some examples of strains being
shared by several patients (affecting two to five patients in the
100
50
Discussion
This report reviews the first 250 cases affected (infected or colonized) by NDM-positive bacteria in the UK, as ascertained from
referrals to PHE’s national reference laboratory. They were recognized over a period of 5.5 years from February 2008 to July 2013.
As such, this analysis presents data for the largest ‘national’ collection of NDM-positive isolates so far reported outside the Indian
subcontinent.
Hospital
% similarity
same centre), most isolates appeared to be sporadic. The four
NDM-positive P. aeruginosa isolates were from different hospitals
and represented distinct strains. Three belonged to international
lineages associated with metallo-b-lactamases (STs 654, 111
and 357); the fourth (VNTR profile 10,2,7,3,6,1,8,5,6) had a
blaVIM allele in addition to blaNDM.
Date
week/year
V
17/2009
E
6/2013
I
45/2008
D
24/2009
N
9/2013
H
26/2009
J
4/2013
O
46/2010
S
22/2013
F
31/2013
K
14/2013
N
4/2013
U
26/2013
M
43/2012
M
48/2012
C
24/2013
A
41/2012
P
45/2012
C
24/2013
R
43/2012
Q
22/2009
T
31/2012
L
17/2010
S
18/2013
D
49/2010
B
49/2012
G
4/2012
D
49/2012
G
52/2011
3
1
2
Figure 3. PFGE profiles of XbaI-digested genomic DNA from NDM-positive isolates of E. coli received between 2008 and July 2013 from 29 patients, showing
clusters of isolates (1–3). Isolates were from hospitals A–V; N is the only hospital shared with Figure 2. The line defining clusters is at 86% similarity.
1782
JAC
NDM carbapenemases in the UK
The majority of isolates were from male patients and from
those .60 years of age. This contrasts with isolates reported
from India by Kumarasamy et al.,10 where the majority of patients
were females with a mean age of 36 years. Isolates were primarily from urine specimens (47%, 152/326), and all the isolates from
primary care were from urine; other frequent sources included
clinical and screening swabs, and bacteraemia. A study from a
tertiary care hospital in north-east India screened 270 isolates
of E. coli for carbapenemases and identified 14 isolates positive
for blaNDM and there, too, the majority of the isolates were urinary
(10/14) and 57% (8/14) were from male patients.23
Although crude travel history data were available for only
40% of our patients, about half of these had travelled to or had
healthcare contact in the Indian subcontinent. Individual patients
had also travelled to countries in central Africa (Democratic
Republic of Congo and Uganda), the Middle East (Egypt and
Kuwait) and Spain. None of these 250 patients had known links
to the Balkans, which is suggested to be a second epicentre for
NDM-positive bacteria.5 Of concern, .40% of the patients for
whom crude travel data were supplied were stated to have no history of foreign travel. We also noted a substantial number of
NDM-positive bacteria from patients treated in primary care. The
age range affected suggests that many may have had previous
healthcare contact, but clearly NDM-positive bacteria may be
found in the community. ‘NDM cases’ without prior contact with
healthcare settings have been reported elsewhere.24,25
The molecular epidemiological knowledge gained so far about
NDM-positive isolates provides evidence both for gene spread
between plasmids with different replicon types and for plasmid
spread between different strains, species and genera.5 There is
much less evidence for extensive dissemination by high-risk
clones, whereas the spread of KPC carbapenemase is strongly
linked to dissemination of K. pneumoniae ST258 and its variants.
In this report, 29% (14/49) of patients with multiple NDM-positive
isolates had isolates of different species or genera. In some
instances it was possible to demonstrate shared plasmids in
such cases (J. Findlay, K. L. Hopkins and N. Woodford, unpublished
data), but the direction of transmission cannot be inferred, nor
can one draw firm conclusions about transfer events within the
affected patient; some patients may have been colonized by multiple NDM-positive strains or species at source. Typing of the isolates, where available, revealed one outbreak of NDM-positive
K. pneumoniae involving 14 patients and identified three clusters
of E. coli, though most of the E. coli isolates within these latter
clusters did not appear to be epidemiologically linked.
Most of the isolates were resistant to all carbapenems tested and
all showed potentiation of imipenem by EDTA, confirming MBL activity. Although aztreonam is not inactivated by NDM (or other
metallo-enzymes), 88% (182/206) of the Enterobacteriaceae isolates tested were resistant, as is frequently the case elsewhere,10,23
almost certainly reflecting the presence of multiple resistance
mechanisms, such as ESBLs and AmpC enzymes.
Among non-b-lactams, ciprofloxacin resistance was seen in
87% (285/326) of NDM-positive isolates. High-level resistance to
the three aminoglycosides tested was seen in 71% (218/306) of
Enterobacteriaceae and in 50% (10/20) of non-fermenters. This
may reflect the production of one or more 16S rRNA methyltransferases. In a recent study,26 isolates with both NDM enzymes and
16S rRNA methyltransferases, including the novel RmtF enzyme,
were described. The majority of our NDM isolates were susceptible
to colistin (90%, 295/326) and tigecycline (57%, 187/326), as also
noted in other studies.10,11 Nevertheless, colistin use may lead to
development of resistance during therapy11 and is potentially
nephrotoxic and neurotoxic. Tigecycline is licensed for complicated abdominal and skin and soft tissue infections and may
not be a suitable agent for treating urinary tract infections
owing to low urinary concentrations.11 In this report, all isolates
obtained from primary care settings were urinary, posing a therapeutic challenge.
Prolonged carriage of NDM-positive isolates has been reported
previously;27,28 here, we found instances of apparent carriage for
.6 months in 14% (7/49) of patients with multiple isolates.
Positive isolates were identified .1 year apart in two cases.
Such patients may act as a reservoir for the spread of NDMpositive bacteria in the hospital and community setting.
The major limitation of our data is the paucity of clinical details
about the patients, including treatments prescribed and outcomes. However, we have summarized available epidemiological
and typing data for 250 cases and 326 NDM-positive isolates identified over 5.5 years in the UK. The dissemination of NDM enzymes
among diverse strains, species and genera of Enterobacteriaceae
and non-fermenters and their frequent multidrug resistance is
clearly demonstrated, with most cases being sporadic. This report
highlights: the need to find effective therapeutic options; the need
for rapid and robust diagnostic tools to aid accurate and prompt
identification of NDM-positive isolates; the desirability of strengthening current surveillance programmes; the need for international
collaboration; and, last but not least, the continuing need for
infection prevention and control processes to limit transmission
within healthcare settings.
Acknowledgements
We are grateful to Claire Perry and Zoë Payne for their help with typing of
the isolates and to Jacqueline Findlay, Zoë Payne and Laura Wright for
carrying out MLST.
Funding
This work was funded internally.
Transparency declarations
D. M. L. is partly self-employed and consults for numerous pharmaceutical
and diagnostic companies, including Achaogen, Adenium, Alere, Allecra,
Astellas, AstraZeneca, Bayer, Basilea, bioMérieux, Bioversys, Cubist,
Curetis, Discuvra, Forest, GSK, Kalidex, Merck, Meiji Seika, Pfizer, Roche,
Tetraphase, VenatoRx and Wockhardt; he holds grants from AstraZeneca,
Basilea, Cubist, Meiji Seika, Merck, VenatoRx and Wockhardt; he has received
lecture honoraria or travel reimbursement from AstraZeneca, Bruker, Curetis,
GSK, J&J, Merck, Novartis, Pfizer and Tetraphase; and he holds shares in
Dechra, GSK, Merck and Pfizer, collectively amounting to ,10% of portfolio
value. All other authors have none to declare.
References
1 Davies SC. Annual Report of the Chief Medical Officer, Volume Two, 2011.
Infections and the Rise of Antimicrobial Resistance. London: Department of
Health, 2013. https://www.gov.uk/government/uploads/system/uploads/
1783
Jain et al.
attachment_data/file/138331/CMO_Annual_Report_Volume_2_2011.pdf
(21 October 2013, date last accessed).
2 Transatlantic Taskforce on Antimicrobial Resistance. Recommendations
for Future Collaboration Between the U.S. and EU, 2011. ECDC Stockholm.
http://ecdc.europa.eu/en/activities/diseaseprogrammes/tatfar/documents/
210911_tatfar_report.pdf (21 October 2013, date last accessed).
3 WHO. The Evolving Threat of Antimicrobial Resistance: Options for Action,
2012. http://whqlibdoc.who.int/publications/2012/9789241503181_eng.
pdf (21 October 2013, date last accessed).
4 Yong D, Toleman MA, Giske CG et al. Characterization of a new
metallo-b-lactamase gene, blaNDM-1, and a novel erythromycin esterase
gene carried on a unique genetic structure in Klebsiella pneumoniae
sequence type 14 from India. Antimicrob Agents Chemother 2009; 53:
5046– 54.
16 Woodford N, Warner M, Pike R et al. Evaluation of a commercial
microarray to detect carbapenemase-producing Enterobacteriaceae.
J Antimicrob Chemother 2011; 66: 2887 –8.
17 Turton JF, Perry C, Elgohari S et al. PCR characterization and typing of
Klebsiella pneumoniae using capsular type-specific, variable number
tandem repeat and virulence gene targets. J Med Microbiol 2010;
59: 541– 7.
18 Al-Agamy MH, Shibl AM, Elkhizzi NA et al. Persistence of Klebsiella
pneumoniae clones with OXA-48 or NDM carbapenemases causing
bacteraemias in a Riyadh hospital. Diagn Microbiol Infect Dis 2013;
76: 214– 6.
19 Diancourt L, Passet V, Verhoef J et al. Multilocus sequence typing of
Klebsiella pneumoniae nosocomial isolates. J Clin Microbiol 2005; 43:
4178– 82.
5 Johnson AP, Woodford N. Global spread of antibiotic resistance: the
example of New Delhi metallo-b-lactamase (NDM)-mediated carbapenem
resistance. J Med Microbiol 2013; 62: 499–513.
20 Turton JF, Turton SE, Yearwood L et al. Evaluation of a nine-locus
variable-number tandem-repeat scheme for typing of Pseudomonas
aeruginosa. Clin Microbiol Infect 2010; 16: 1111– 6.
6 Struelens MJ, Monnet DL, Magiorakos AP et al. and European NDM-1
survey participants. New Delhi metallo-b-lactamase 1-producing
Enterobacteriaceae: emergence and response in Europe. Euro Surveill
2010; 15: pii¼19716.
21 Curran B, Jonas D, Grundmann H et al. Development of a multilocus
sequence typing scheme for the opportunistic pathogen Pseudomonas
aeruginosa. J Clin Microbiol 2004; 42: 5644 –9.
7 Jovcic B, Lepsanovic Z, Suljagic V et al. Emergence of NDM-1
metallo-b-lactamase in Pseudomonas aeruginosa clinical isolates from
Serbia. Antimicrob Agents Chemother 2011; 55: 3929– 31.
8 Mazzariol A, Bošnjak Z, Ballarini P et al. NDM-1-producing Klebsiella
pneumoniae, Croatia. Emerg Infect Dis 2012; 18: 532– 4.
9 Queenan AM, Bush K. Carbapenemases: the versatile b-lactamases. Clin
Microbiol Rev 2007; 20: 440– 58.
22 Wirth T, Falush D, Lan R et al. Sex and virulence in Escherichia coli: an
evolutionary perspective. Mol Microbiol 2006; 60: 1136– 51.
23 Bora A, Ahmed GU, Hazarika NK et al. Incidence of bla NDM-1 gene in
Escherichia coli isolates at a tertiary care referral hospital in Northeast
India. Indian J Med Microbiol 2013; 31: 250–6.
24 Nordmann P, Couard J-P, Sansot D et al. Emergence of an
autochthonous and community-acquired NDM-1-producing Klebsiella
pneumoniae in Europe. Clin Infect Dis 2012; 54: 150–1.
10 Kumarasamy KK, Toleman MA, Walsh TR et al. Emergence of a new
antibiotic resistance mechanism in India, Pakistan, and the UK: a
molecular, biological, and epidemiological study. Lancet Infect Dis 2010;
10: 597– 602.
25 Kus JV, Tadros M, Simor A et al. New Delhi metallo-b-lactamase-1:
local acquisition in Ontario, Canada, and challenges in detection. CMAJ
2011; 183: 1257– 61.
11 Livermore DM, Warner M, Mushtaq S et al. What remains against
carbapenem-resistant Enterobacteriaceae? Evaluation of chloramphenicol,
ciprofloxacin, colistin, fosfomycin, minocycline, nitrofurantoin, temocillin
and tigecycline. Int J Antimicrob Agents 2011; 37: 415–9.
26 Hidalgo L, Hopkins KL, Gutierrez B et al. Association of the novel
aminoglycoside resistance determinant RmtF with NDM carbapenemase
in Enterobacteriaceae isolated in India and the UK. J Antimicrob
Chemother 2013; 68: 1543– 50.
12 Andrews JM. Determination of minimum inhibitory concentrations.
J Antimicrob Chemother 2001; 48 Suppl 1: 5 –16.
27 D’Andrea MM, Venturelli C, Giani T et al. Persistent carriage and
infection by multidrug-resistant Escherichia coli ST405 producing NDM-1
carbapenemase: report on the first Italian cases. J Clin Microbiol 2011;
49: 2755 –8.
13 BSAC. BSAC Methods for Antimicrobial Susceptibility Testing Version 12,
2013. http://bsac.org.uk/wp-content/uploads/2012/02/Version-12-Apr2013_final.pdf (21 October 2013, date last accessed).
14 Ellington MJ, Kistler J, Livermore DM et al. Multiplex PCR for rapid
detection of genes encoding acquired metallo-b-lactamases. J Antimicrob
Chemother 2007; 59: 321–2.
15 Mushtaq S, Irfan S, Sarma JB et al. Phylogenetic diversity of Escherichia
coli strains producing NDM-type carbapenemases. J Antimicrob Chemother
2011; 66: 2002– 5.
1784
28 Kim M-N, Yong D, An D et al. Nosocomial clustering of NDM-1-producing
Klebsiella pneumoniae sequence type 340 strains in four patients at a South
Korean tertiary care hospital. J Clin Microbiol 2012; 50: 1433–6.
29 EUCAST. Breakpoint Tables for Interpretation of MICs and Zone
Diameters. Version 3.1, 2013. http://www.eucast.org/fileadmin/src/
media/PDFs/EUCAST_files/Breakpoint_tables/Breakpoint_table_v_3.1.pdf
(21 October 2013, date last accessed).