Routes of transmission of VIM-positive Pseudomonas aeruginosa in the adult intensive care unit-analysis of 9 years of surveillance at a university hospital using a mathematical model

Thi Mui Pham, Andrea C Büchler, Anne F Voor In 't Holt, Juliëtte A Severin, Martin C J Bootsma, Diederik Gommers, Mirjam E Kretzschmar, Margreet C Vos

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BACKGROUND: Hospital outbreaks of multidrug resistant Pseudomonas aeruginosa are often caused by Pseudomonas aeruginosa clones which produce metallo-β-lactamases, such as Verona Integron-encoded Metallo-β-lactamase (VIM). Although different sources have been identified, the exact transmission routes often remain unknown. However, quantifying the role of different transmission routes of VIM-PA is important for tailoring infection prevention and control measures. The aim of this study is to quantify the relative importance of different transmission routes by applying a mathematical transmission model using admission and discharge dates as well as surveillance culture data of patients.

METHODS: We analyzed VIM-PA surveillance data collected between 2010 and 2018 of two intensive-care unit (ICU) wards for adult patients of the Erasmus University Medical Center Rotterdam using a mathematical transmission model. We distinguished two transmission routes: direct cross-transmission and a persistent environmental route. Based on admission, discharge dates, and surveillance cultures, we estimated the proportion of transmissions assigned to each of the routes.

RESULTS: Our study shows that only 13.7% (95% CI 1.4%, 29%) of the transmissions that occurred in these two ICU wards were likely caused by cross-transmission, leaving the vast majority of transmissions (86.3%, 95% CI 71%, 98.6%) due to persistent environmental contamination.

CONCLUSIONS: Our results emphasize that persistent contamination of the environment may be an important driver of nosocomial transmissions of VIM-PA in ICUs. To minimize the transmission risk from the environment, potential reservoirs should be regularly and thoroughly cleaned and disinfected, or redesigned.

Original languageEnglish
Article number55
Pages (from-to)55
JournalAntimicrobial Resistance and Infection Control
Issue number1
Publication statusPublished - 4 Apr 2022

Bibliographical note

Funding Information:
Forschungsfonds zur Förderung exzellenter Nachwuchsforschender der Universität Basel, University of Basel, Basel, Switzerland (ACB). TMP has received support from the Innovative Medicines Initiative Joint Undertaking under grant agreement no. 115737-1 (Combatting bacterial resistance in Europe - molecules gainst Gram negative infections (COMBACTE-MAGNET)), resources of which are composed of financial contribution from the European Union Seventh Framework Programme (FP 7/2007-2013) and EFPIA companies in kind contribution. The funders had no role in data collection and analysis, decision to publish, or preparation of the manuscript. (

Funding Information:
We would like to thank the infection control practitioners from the Erasmus MC, especially Inge de Goeij, for their cooperation and support.

Publisher Copyright:
© 2022, The Author(s).


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