Rapid communications Outbreak of NDM-1-producing Acinetobacter baumannii in France , January to May 2013

J W Decousser (jean-winoc.decousser@hmn.aphp.fr)1,2, C Jansen2,3, P Nordmann4,5, A Emirian1,2, R A Bonnin4, L Anais1, J C Merle6, L Poirel4,5 1. Department of Virology, Bacteriology Infection Control, Parasitology –Mycology, Assistance Publique – Hôpitaux de Paris (AP-HP), University Hospital Henri Mondor, Créteil, France 2. University Paris East Créteil (UPEC), Faculty of Medicine, Créteil, France 3. Infection Control, Prevention and Epidemiology Unit, AP-HP, University Hospital Henri Mondor, Créteil, France 4. INSERM U914 ‘Emerging Antibiotic Resistance’, Le-Kremlin-Bicêtre, France 5. Medical and Molecular Microbiology Unit, Department of Medicine, Faculty of Science, University of Fribourg, Fribourg, Switzerland 6. Department of Anaesthesiology, AP-HP, University Hospital Henri Mondor, Créteil, France


Background
The emergence and spread of New-Delhi metallo-betalactamase (NDM)-producing Gram negative isolates constitutes a new wave of multidrug-resistant (MDR) bacteria [1].First identified from Enterobacteriaceae, the bla NDM gene has since been identified in non-fermenting bacterial species such as Pseudomonas aeruginosa and Acinetobacter baumannii [2,3].Considering its ability to be the source of nosocomial outbreaks, carbapenem-resistant A. baumannii (AB) represents a threat for critically ill hospitalised patients [4].We report here the first outbreak of NDM-1-producing AB in Europe, which occurred in a French surgical intensive-care unit in January to May 2013.

Outbreak description
The index case (Patient 1) was a female patient in her early 80s suffering from end-stage cirrhosis.She originated from Algeria but lived mostly in France.During a stay in Algeria in December 2012, she was admitted into a private hospital in the city of Tizi Ouzou following renal failure, which required dialysis.After one month in hospital, she was repatriated to France due to liver decompensation.On 18 January 2013, she was admitted to a 15-bed surgical intensive-care unit of a tertiary care university hospital in a Paris suburb.In accordance with local and national policy, she was screened on admission for carriage of MDR bacteria.Rectal screening revealed MDR-A.baumannii (MDR-AB) (Isolate 1) that was susceptible only to amikacin, netilmicin and colistin (Table ).The same day, she was intubated for respiratory failure.Protected distal bronchial brushing yielded a culture of MDR-AB with the same antibiotic resistance profile.A combination of intravenous tigecycline and amikacin was given.On 24 January, she developed multivisceral failure and died four days later.During the following days, three additional patients with MDR-AB infection and/or colonisation were identified in the same unit.A cirrhotic male patient in his mid-60s (Patient 2) -who had been hospitalised since 3 January 2013 and confirmed free of MDR bacteria on admission -developed a ventilator-associated pneumonia on 26 January.Culture of a distal protected specimen yielded MDR-AB (Isolate 2).This patient was successfully treated by a combination of tigecycline and amikacin and was extubated two days later.Patient 3 was a male liver-transplant patient in his mid-60s who was not colonised on admission but developed a dialysis catheter-related bloodstream infection due to a MDR-AB on 28 January (Isolate 3).Imipenem and amikacin combination was prescribed but the patient died of haemorrhagic shock before antibacterial susceptibility results could be obtained.Patient 4 was a dual renal-and liver-transplant female patient in her late 40s from whom an abdominal drain yielded an MDR-AB culture on 2 February (Isolate 4).This patient recovered without receiving any antibiotic therapy and was discharged from the hospital on 11 February.
Two weeks after the admission of the index case, a woman in her early 80s (Patient 5) suffered from a cerebrovascular accident and was repatriated from the same Algerian county that Patient 1 was repatriated from (but from a different healthcare facility) to the emergency unit of our hospital.A screening test performed on admission identified MDR-AB (Isolate 5).
Two months after this first cluster of five patients with MDR-AB, two additional patients free of MDR bacteria on admission to the surgical intensive-care unit described acquired a MDR-AB during their stay in this unit.A woman in her late 50s (Patient 6) was admitted to the surgical intensive-care unit on 6 April and placed in the room where the index case had stayed.This patient was found positive for MDR-AB on 15 April in specimens from a catheter and the respiratory tract (Isolate 6).She was treated with intravenous tigecycline and aerosolised colistin.She underwent successful liver transplantation on 22 April and recovered well.The last patient (Patient 7) was a man in his late 50s admitted to the surgical intensive-care unit on 3 April for a liver transplant and from whom a rectal swab yielded MDR-AB a month later (Isolate 7).The patients' duration of hospital stay, time of infection and/or colonisation and location in the hospital are reported in Figure 1.

Laboratory analysis
Identification of the seven MDR-AB strains at the species level was confirmed by 16S RNA sequencing (data not shown).Their antimicrobial susceptibilities were tested by minimum inhibitory concentration (MIC) determination (Etest, bioMérieux, France) (Table ) and interpreted according to EUCAST guidelines [5].All isolates exhibited a high level of resistance to penicillins, broad-spectrum cephalosporins, carbapenems, fluoroquinolones and trimethoprim-sulfamethoxazole.Those isolates remained susceptible only to netilmicin, colistin and amikacin.The production of a class B carbapenemase was suspected by the positive results of the imipenem/imipenem plus EDTA test using MIC double strips (Etest, bioMérieux, France) (Table 1) and confirmed by UV spectrophotometry [6].Carbapenemase genes were screened by PCR as described and the bla NDM-1 gene was amplified in the seven isolates [7].Genotypic comparison by pulsed-field gel electrophoresis using restriction enzyme SmaI revealed an indistinguishable profile (data not shown).Diversilab (bioMérieux, France) analysis and multilocus sequence typing (MLST) typing confirmed that these isolates were clonally related and belonged to the same sequence type, ST85 (Figure 2) [8].The genetic environment of blaNDM-1 was investigated as previously described [8] and showed that it was located in the composite transposon Tn125 made of two copies of insertion sequence (IS) ISAba125.

Discussion
Carbapenem-resistant A. baumannii are a source of deep concern due to their multidrug resistance pattern and the ability of this bacterial species to persist in the environment [4,9,10].Intensive-care units are particularly susceptible to outbreaks associated with  MDR-AB: it is sometimes difficult for them to adhere strictly to infection control measures when patients require a high and persistent care-load.Four years ago, the same hospital faced a hospital-wide outbreak of MDR-AB colonisations and infections due to the importation of an index case from Tahiti [11].Despite this experience and the implementation in 2010 at the national and local level of strict measures on hospital admission to detect, screen and place under contactisolation precautions repatriated patients, another outbreak linked to the admission of a patient previously hospitalised abroad again occurred [12].
Since 2010, NDM-producing MDR-AB has been identified in various parts of the world, in particular in North Africa and the Middle East [8,[13][14][15][16][17].A series of imported cases have been identified recently in Europe, such as in the Czech Republic, Germany, Slovenia, Switzerland and Belgium [8,13,14,17].In France, the emergence of an NDM-1-producing MDR-AB strain originating from North Africa was recently highlighted [15,17].We describe here the first outbreak associated with the importation of this NDM-  The isolates from the hospitalised patients were compared with a collection of characterised strains [8,17].A similarity line (89.4%)shows the cut-off to separate different clones.
molecular-based methods of detection may help to control such outbreaks.
Taking in account the relationship between North African countries and many European countries, it is possible that the spread of NDM-1 carbapenemase may occur rapidly, mostly through A. baumannii rather than Enterobacteriacae, since A. baumannii may become much more difficult to eradicate.