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.
Bibliographical noteFunding 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. (www.imi.europa.eu).
We would like to thank the infection control practitioners from the Erasmus MC, especially Inge de Goeij, for their cooperation and support.
© 2022, The Author(s).