Five-year VIM-producing Pseudomonas aeruginosa outbreak in four Belgian ICUs, an investigation report (2019-2023)

Area of Science:

• Medical Microbiology
• Infectious Disease Epidemiology
• Public Health

Background:

• Outbreaks of Verona integron-encoded metallo-β-lactamase-producing Pseudomonas aeruginosa (VIM-PA) are frequently associated with contaminated intensive care unit (ICU) sink drains.
• This study investigated a VIM-PA outbreak spanning 5 years at four ICUs in a Belgian university center.

Purpose of the Study:

• To investigate the source and clonal diversity of a prolonged VIM-PA outbreak in multiple ICUs.
• To analyze the epidemiological trends and identify risk factors associated with VIM-PA transmission.
• To inform targeted infection control interventions.

Main Methods:

• Retrospective data collection from 01/01/2019 to 30/07/2023.
• Whole-genome sequencing (WGS) and core genome multilocus sequencing typing (cgMLST) for VIM-PA isolate clonality confirmation.
• Regression modeling to estimate new case incidence based on weekly data of at-risk and colonized patients.

Main Results:

• Fifty-one patients were colonized, with 32 infected by VIM-PA, leading to 7 deaths.
• VIM-PA was detected in 47% of examined sink drains.
• Two major VIM-PA clones (ST111 and ST17) were identified, with ST111 being predominant.
• New case incidence rates varied significantly between ICUs.

Conclusions:

• The 5-year outbreak was driven by two VIM-PA clones with minimal genetic evolution, linked to sink-drain contamination.
• Statistical modeling revealed distinct incidence rates across different ICUs, highlighting unit-specific transmission dynamics.
• Prioritization of tailored interventions based on epidemiological findings is crucial for outbreak control.