An Irish outbreak of New Delhi metallo-β-lactamase (NDM)-1 carbapenemase-producing Enterobacteriaceae: increasing but unrecognized prevalence.
BACKGROUND
Carbapenemase-producing Enterobacteriaceae (CPE) may cause healthcare-associated infections with high mortality rates. New Delhi metallo-β-lactamase-1 (NDM-1) is among the most recently discovered carbapenemases.


OBJECTIVE
To report the first outbreak of NDM-1 CPE in Ireland, including microbiological and epidemiological characteristics, and assessing the impact of infection prevention and control measures.


METHODS
This was a retrospective microbiological and epidemiological review. Cases were defined as patients with a CPE-positive culture. Contacts were designated as roommates or ward mates.


RESULTS
This outbreak involved 10 patients with a median age of 71 years (range: 45-90), located in three separate but affiliated healthcare facilities. One patient was infected (the index case); the nine others were colonized. Nine NDM-1-producing Klebsiella pneumoniae, an NDM-1-producing Escherichia coli and a K. pneumoniae carbapenemase (KPC)-producing Enterobacter cloacae were detected between week 24, 2014 and week 37, 2014. Pulsed-field gel electrophoresis demonstrated similarity. NDM-1-positive isolates were meropenem resistant with minimum inhibitory concentrations (MICs) ranging from 12 to 32 μg/mL. All were tigecycline susceptible (MICs ≤1 μg/mL). One isolate was colistin resistant (MIC 4.0 μg/mL; mcr-1 gene not detected). In 2015, four further NDM-1 isolates were detected.


CONCLUSIONS
The successful management of this outbreak was achieved via the prompt implementation of enhanced infection prevention and control practices to prevent transmission. These patients did not have a history of travel outside of Ireland, but several had frequent hospitalizations in Ireland, raising concerns regarding the possibility of increasing but unrecognized prevalence of NDM-1 and potential decline in value of travel history as a marker of colonization risk.
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland; Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
C
C
O'Connor
School of Medicine National University of Ireland Galway, Galway, Ireland; Carbapenemase-Producing Enterobacteriaceae (CPE) Reference Laboratory, Department of Medical Microbiology, University Hospital Galway, Galway, Ireland.
M
M
Cormican
School of Medicine National University of Ireland Galway, Galway, Ireland; Carbapenemase-Producing Enterobacteriaceae (CPE) Reference Laboratory, Department of Medical Microbiology, University Hospital Galway, Galway, Ireland.
T W
TW
Boo
Carbapenemase-Producing Enterobacteriaceae (CPE) Reference Laboratory, Department of Medical Microbiology, University Hospital Galway, Galway, Ireland.
E
E
McGrath
Department of Infection Prevention and Control, University Hospital Limerick, Limerick, Ireland.
B
B
Slevin
Department of Infection Prevention and Control, University Hospital Limerick, Limerick, Ireland.
A
A
O'Gorman
Department of Infection Prevention and Control, University Hospital Limerick, Limerick, Ireland.
M
M
Commane
Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
S
S
Mahony
Department of Infection Prevention and Control, University Hospital Limerick, Limerick, Ireland.
E
E
O'Donovan
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland.
J
J
Powell
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland.
R
R
Monahan
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland.
C
C
Finnegan
Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
M G
MG
Kiernan
Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
J C
JC
Coffey
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland.
L
L
Power
Department of Clinical Microbiology, University Hospital Limerick, Limerick, Ireland; Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland.
N H
NH
O'Connell
Centre for Interventions in Infection, Inflammation & Immunity (4i) and Graduate Entry Medical School, University of Limerick, Limerick, Ireland. Electronic address: colum.dunne@ul.ie.
C P
CP
Dunne
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D018562:Disease Transmission, Infectious / Q000517:prevention & control; D016521:Electrophoresis, Gel, Pulsed-Field; D004755:Enterobacteriaceae / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D006801:Humans; D017053:Infection Control / Q000379:methods; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058889:Molecular Typing; D015995:Prevalence; D012189:Retrospective Studies; D001618:beta-Lactamases / Q000378:metabolism*
D001618:beta-Lactamases; C552864:beta-lactamase NDM-1
Carbapenemase-producing Enterobacteriaceae; Ireland; Multidrug-resistant organism; New Delhi metallo-β-lactamase-1 (NDM-1); Outbreak