To the Editor: During the past decade, enterobacteria that produce Klebsiella pneumoniae
carbapenemase (KPC) have become established in the United States and countries in
South America and Europe (
1
). In Asia, KPC was reported in the People’s Republic of China in 2007 (
2
) and subsequently in South Korea (
3
) and Taiwan (
4
). Public health agencies emphasize screening and strict contact precautions to control
multidrug resistant Enterobacteriaceae (
5
). Routine testing for mechanisms of resistance facilitates detection of emerging
carbapenem-resistant Enterobacteriaceae.
In Singapore's 1,000-bed National University Hospital during November 2010–January
2011, we identified New Delhi metallo-β-lactamase 1–producing Enterobacteriaceae in
2 clinical specimens but none that produced KPC (I. Venkatachalam et al., unpub. data).
We conducted a laboratory screening study to determine the prevalence and nature of
carbapenem-resistant Enterobacteriacea in April 2011. Ethics committee approval was
waived for this study.
Testing of rectal swab samples is part of an established hospitalwide program for
vancomycin-resistant enterococci screening. Using a scoring system to identify patients
at high risk for vancomycin-resistant enterococci (
6
), we found that ≈2.5 specimens per 100 admissions were attained each month. During
our study, we also tested these samples for carbapenemase-producing Enterobacteriaceae.
During April–June 2011, we incubated specimens for 24 h in 10 mL tryptic soy broth
containing 1 mg/L imipenem, then streaked 100 µL of the broth onto CHROMagar KPC (CHROMagar,
Paris, France). Colonies detected after 24 h incubation at 35°C were identified by
using MALDI-TOF MS with a Microflex LT instrument (Bruker Daltonik GmbH, Leipzig,
Germany). Imipenem and meropenem MICs for Enterobacteriacaeae were confirmed by using
Etests (bioMérieux, Marcy l'Etoile, France). Isolates with MIC >2 µg/mL underwent
analysis with /Metallo-β-Lactamase Confirmative Identification Pack (Rosco Diagnostica,
Taastrup, Denmark) and Etest MBL (bioMérieux) for metallo-β-lactamase production.
Isolates suspected to be producers were genotypically confirmed by PCR.
Of the 201 nonduplicate samples processed, 79 microorganisms exhibited imipenem resistance
and were isolated on CHROMagar KPC (Table). Among Enterobacteriaceae, carbapenem MIC
>2 μg/mL was present in 1 E. aerogenes, 2 E. cloacae, and 4 K. pneumoniae isolates.
One isolate (K. pneumoniae) had a positive combined disc test result with a pattern
suggestive of serine carbapenemase production.
Table
Bacteria isolated on CHROMagar in screening for carbapenemase-producing Enterobacteriaceae,
Singapore, 2011*
Organism
No. isolated
Enterobacteriaceae
Klebsiella pneumoniae
11
Enterobacter cloacae
3
Enterobacter aerogenes
2
Proteus mirabilis
2
Escherichia coli
1
Serratia marcescens
1
Non-Enterobacteriaceae: gram-negative nonfermenters
Pseudomonas aeruginosa
20
Acinetobacter baumannii
17
Stenotrophomonas maltophilia
13
Elizabethkingia meningoseptica
3
Wautersiella falsenii
1
Enterococci
Enterococcus gallinarum
4
Enterococcus faecalis
1
*CHROMagar, Paris, France.
We analyzed genomic DNA (DNeasy Blood and Tissue Kit, QIAGEN, Hilden, Germany) from
this isolate by using PCR for transmissible carbapenem resistance markers: metallo-β-lactamases
(VIM, IMP, and KHM-1), serine carbapenemases (KPC, GES1–5 and 7), and OXA-48. bla
KPC-specific primers (forward primer 5′-CGTTGACGCCCAATCC-3′; reverse primer 5′-ACCGCTGGCAGCTGG-3′)
generated a 390-bp amplicon. Full gene sequencing of bla
KPC (forward primer 5′-ATGTCACTGTATCGCCGTCT-3′; reverse primer 5′-CCTAAATGTGACAGTGGTTGG)
revealed 100% homology to bla
KPC-2 (GenBank accession no. FJ628167.2). Further analysis showed that the isolate
carried extended-spectrum β-lactamase (bla
TEM-1, bla
SHV-11, bla
CTX-M-15), plasmid-located AmpC (bla
DHA-1), and 16S rRNA methylase armA genes but was negative for bla
CMY, bla
OXA, bla
GES, metallo-β-lactamases, and plasmid-mediated quinolone (qnr) genes. Multilocus
sequence typing conducted at Institut Pasteur (Paris, France), identified this isolate
as sequence type 11. It was susceptible only to colistin and tigecycline.
Sequence type 11, a single-locus variant of the internationally dominant sequence
type 258 clone (
7
), is present in 64.2% of KPC-producing K. pneumoniae in China (
8
). In South Korea, sequence type 11 is the most common clone of extended-spectrum
β-lactamase–producing K. pneumoniae isolates (
3
).
The KPC-producing K. pneumoniae originated from a woman in the local community, 89
years of age, who had severe ischemic cardiomyopathy and atrial fibrillation. She
was discharged home after a 3-day hospitalization for treatment of stroke in January
2011. During May 2011, she was readmitted after a severe stroke. During week 4, she
was transferred to a subacute care hospital but readmitted within 24 hours with a
lower respiratory tract infection. A rectal swab sample was collected for routine
screening for vancomycin-resistant enterococci. We empirically prescribed a 10-day
course of piperacillin-tazobactam. On day 10 of treatment, KPC-producing K. pneumoniae
was isolated from the rectal specimen. The patient responded to treatment and was
discharged to a long-term care facility.
This case demonstrates concerns about a KPC of local community origin because no other
KPC-producing Enterobacteriaceae were isolated during this inpatient surveillance
and the patient had neither received antimicrobial drugs nor traveled in the 6 months
before her May admission (
7
). However, she was admitted 3 weeks before sampling; an unidentified hospital source
remains a possibility. Of added concern is the potential for dissemination within
the facility to which she was discharged.
Resistance to third-generation cephalosporins was reported for 20% of Escherichia
coli, 32.3% of K. pneumoniae, 46.2% of Acinetobacter spp., and 7.5% of Pseudomonas
aeruginosa clinical isolates at 4 major Singapore hospitals during January 2006–December
2008 (
9
). Authors reported positive correlation between meropenem administration and carbapenem
resistance development in Acinetobacter spp. blood isolates.
When the resistance mechanism to an antimicrobial drug is embedded in highly mobile
elements like plasmids, widespread dissemination is possible. Although acute care
hospitals are conducive to development of antimicrobial drug resistance, long-term
care facilities facilitate spread of these organisms (
10
). Infection control interventions including routine screening for mechanisms of resistance
and responsible use of antimicrobial drugs are increasingly critical in hospitals
and long-term care facilities; a response plan coordinated between these facilities
is needed.