# Hospital outbreak of NDM-producing Klebsiella pneumoniae in a surgical intensive care unit: sink traps as the causing source of epidemic strain resurgence

Céline Bourigault, Anaïs Andreo, Reynald Mangeant, Florence Le Gallou, Géraldine Marquot, Dominique Demeure Dit Latte, Pierre-Joachim Mahé, Gabriel Birgand, Chrystèle Bidon, Karim Asehnoune, et al.

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## To cite this version:

Céline Bourigault, Anaïs Andreo, Reynald Mangeant, Florence Le Gallou, Géraldine Marquot, et al. Hospital outbreak of NDM-producing Klebsiella pneumoniae in a surgical intensive care unit: sink traps as the causing source of epidemic strain resurgence. American Journal of Infection Control, 2025, S0196-6553 (25), pp.00004-00005. 10.1016/j.ajic.2025.01.003. inserm-04886251

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Contents lists available at [ScienceDirect](https://www.sciencedirect.com)

American Journal of Infection Control

journal homepage: [www.ajicjournal.org](https://www.ajicjournal.org)

AJIC
American Journal of
Infection Control

## Brief Report

# Hospital outbreak of NDM-producing *Klebsiella pneumoniae* in a surgical intensive care unit: Sink traps as the causing source of epidemic strain resurgence

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Céline Bourigault PharmD, MSc<sup>a,∗</sup>, Anaïs Andreo PharmD, MSc<sup>a</sup>, Reynald Mangeant PharmD, PhD<sup>a</sup>, Florence Le Gallou PharmD<sup>a</sup>, Géraldine Marquot PharmD<sup>a</sup>, Dominique Demeure Dit Latte MD<sup>b</sup>, Pierre-Joachim Mahé MD<sup>b</sup>, Gabriel Birgand PharmD, PhD<sup>c</sup>, Chrystèle Bidon NP<sup>a</sup>, Karim Asehnoune MD, PhD<sup>b</sup>, Stéphane Corvec PharmD, PhD<sup>d</sup>, Didier Lepelletier MD, PhD<sup>a</sup>

**Key Words:**

Carbapenemase-producing *Enterobacterales*

Outbreak

Environmental reservoir

We report the management of a New Delhi metallo-β-lactamase-producing *Klebsiella pneumoniae* outbreak in a surgical intensive care unit over 1 year. New Delhi metallo-β-lactamase-producing *Enterobacterales* were isolated from sink traps. The installation of new sink traps closed the outbreak. Environmental reservoirs should be considered for any persistent carbapenemase-producing *Enterobacterales* outbreak.

© 2025 The Author(s). Published by Elsevier Inc. on behalf of Association for Professionals in Infection Control and Epidemiology, Inc. This is an open access article under the CC BY license ([http://creativecommons.org/licenses/by/4.0/](http://creativecommons.org/licenses/by/4.0/)).

## INTRODUCTION

Carbapenemase-producing *Enterobacterales* (CPE) have become a major problem for health care settings.¹ Treatment of patients infected by CPE is a challenge since only a few drugs remain active against these bacteria.

CPE spreads from person to person through contact with infected or colonized people. In addition, they can transmit their genetic material to other bacteria, leading to the rapid spread of resistance.² The hospital environment can also be an important source of pathogens and nosocomial CPE outbreaks.³⁻⁶

Herein, we describe a prolonged New Delhi metallo-β-lactamase-producing *Klebsiella pneumoniae* (NDM-KP) outbreak in a surgical intensive care unit (ICU) of a French University hospital.

## METHODS

### Setting

The Nantes University Hospital is a 3,000-bed facility. The surgical ICU is composed of 31 single rooms, each with a sink for hand washing or evacuation of care liquids.

### Case definition

The index case is a 71-year-old patient, with no history of hospitalization abroad or CPE carriage. A NDM-KP strain was isolated on September 18, 2018 (blood culture), 8 days after admission in the ICU. The patient died on September 20, 2018 from a septic shock despite probabilist antibiotic therapy with meropenem/ciprofloxacin/linezolide.

A case was defined as any patient hospitalized in the surgical ICU between September 10, 2018 and July 4, 2019, with a positive NDM-KP culture.

<footnote><sup>a</sup> Infection Control Department, Nantes University Hospital, Nantes, France</footnote>

<footnote><sup>b</sup> Surgical Intensive Care Unit, Nantes University Hospital, Nantes, France</footnote>

<footnote><sup>c</sup> Regional Center for Infection Prevention and Control, Nantes University Hospital, Nantes, France</footnote>

<footnote><sup>d</sup> Bacteriology Department, Nantes University Hospital, INSERM, INCIT U1302, Nantes, France</footnote>

<footnote>* Address correspondence to Céline Bourigault, PharmD, MSc, Unité de Gestion du Risque Infectieux, Bâtiment le Tourville, 5 rue du Pr Boquien, 44093 Nantes Cedex, France.</footnote>

<footnote>E-mail address: celine.bourigault@chu-nantes.fr (C. Bourigault).</footnote>

<footnote>Funding/support: None.</footnote>

<footnote>Conflicts of interest: None to report.</footnote>
## Patients' management and prevention measures

A multidisciplinary team coordinated the investigations. Infection control measures were implemented in the surgical ICU in accordance with national recommendations.⁷ During the outbreak period, all patients were screened weekly in the ICU with rectal swabs until the end of August 2019. Regular educational interventions were implemented in the ICU and focused on hand hygiene, contact precautions, and environmental cleaning. An audit was conducted in June 2019 to evaluate infection control measures.

## Environmental policy and sampling

For all patients in the ICU, the room and medical equipment were disinfected daily with a detergent-disinfectant (Surfanios premium, Anios, France). After CPE patients discharge, airborne disinfection with hydrogen peroxide and peracetic acid (RHEA, Airinspace, France) was systematically conducted in the room. Starting from January 2019, all sink traps in the ICU were bleached weekly (2.6% active chlorine, 300 mL).

Environmental samples in the ICU were collected in January, March, and June 2019 with eswabs (Environmental swab system Copan, Italy).

## Microbiological methods

Stool and environmental samples collected were seeded and cultured on selective chromogenic media (chromID Carba-Smart ID; bioMérieux, France). Bacterial identification was performed by using VitekMS MALDI-TOF technology (bioMérieux). Resist-4 O.K.N.V. immunochromatographic lateral flow assays (Coris BioConcept, Belgium) were used to confirm the

suspected resistance phenotype. NDM-KP strains were compared by pulsed-field gel electrophoresis as previously reported.⁸

## RESULTS

From September 10, 2018 to July 4, 2019, 9 patients were colonized or infected with NDM-KP (Fig. 1). The median length of stay for CPE patients in the ICU was 19 days (min-max: 1-67 days). The median time from admission in the ICU to NDM-KP detection was 11 days (min-max: 4-32 days). All patients with CPE were hospitalized in sector 2 (Fig. 2) and were identified over 3 separate periods, 8 weeks and 4 weeks, respectively, with no NDM-KP positive-patient present between the different periods (Fig. 1). During the outbreak period, 377 contact patients were identified and 883 rectal screenings were performed.

A total of 49 environmental samplings were collected in the ICU. The NDM-KP epidemic strain was isolated in the sink of room 31 and an NDM-producing *Enterobacter cloacae* complex was found in the sink of room 21. All other samples were negative for NDM-producing *Enterobacterales* (Supplementary Material). The NDM-KP strains isolated from the 9 positive patients and the environmental strain (room 31) were identical (> 98% similarity, data not shown).

The audit revealed insufficient hand hygiene compliance among HCWs. Dialysis liquids were also drained directly into the sink of the patient's room, right next to the medication preparation plan. In the second phase, all care fluids of CPE patients were gelled and eliminated as infectious risk waste to avoid disposal in the sink.

In August 2019, a new system (HygieneSiphon, Aquafree, Germany) was installed in all sink traps of the ICU's rooms. This system limits aerosolization from stagnant water in the sink trap and reduces biofilm (Supplementary material).

<figure><img src="image_5.png" /><figcaption>**Fig. 1.** Periods of New Delhi metallo-β-lactamase-producing *K. pneumoniae* patients' hospitalizations and chronology of infection control measures implemented.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Geographical distribution of NDM-producing *K. pneumoniae* patients in the intensive care unit. NDM, New Delhi metallo-β-lactamase.</figcaption></figure>

## DISCUSSION

We report the management of an NDM-KP outbreak in a surgical ICU, with sink traps as a possible source of transmission.

Strict application of infection control measures and regular educations among HCW were not sufficient to control this outbreak.⁷ The absence of a positive patient with NDM-KP strain between each period and the presence of all cases in the same part of the ICU suggested the presence of an environmental reservoir.

Environmental samples from the sinks isolated 2 NDM-producing *Enterobacteriales* in rooms 31 and 21. During the outbreak period, a weekly disinfection of all sinks was implemented with bleach, which may explain why most of the sinks were negative.

Patient-to-patient transmission is considered as the major route of CPE transmission, but hospital water environment is now increasing recognized as a potential source of CPE outbreaks.³⁻⁵,⁹ In our outbreak, we assume that direct evacuation of care liquids in the sink of the patient's room leads to colonization of sink traps by multiresistant bacteria. The risk of aerosolization when using taps can lead to contamination of the patient's environment. The installation of new sink traps limiting the production of aerosol from

stagnant water has been an effective measure, since no new case has been identified in screenings conducted up to August 2019.

Other interventions to control waterborne reservoirs have been reported in the literature and may be considered as an alternative to these HygieneSiphon: waterless ICU, chemical treatment of drains, or thermal disinfection.¹⁰

## CONCLUSIONS

We report the control of an NDM-KP outbreak in a surgical ICU over 1 year. The contaminated sink traps were probably a source of contamination in this outbreak and explained the duration of this outbreak. For persistent outbreaks in the ICU, attention should focus on sink contamination in addition to infection control measures.

## Acknowledgments

We thank all surgical ICU staff for their collaboration in the management of this outbreak.
# APPENDIX A. SUPPLEMENTARY DATA

Supplementary data related to this article can be found at doi:10.1016/j.ajic.2025.01.003.

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