The risk of contaminated ultrasound gels in the intensive care unit: lessons from an outbreak of .

Background: is an environmental Gram-negative bacterium, resistant to many antibiotics and antiseptics, that can survive in aqueous hospital environments. We investigated an outbreak of in the intensive care unit (ICU) of Ng Teng Fong General Hospital, aiming to identify the source and prevent further transmission.

Methods: The outbreak was detected after two ICU patients developed bacteremia. Environmental samples, including ultrasound gels, and disinfectants, were collected. Whole genome sequencing (WGS) was used to determine clonality between clinical and environmental isolates. Immediate actions were taken, including a recall of ultrasound gel batches and the use of sterile gel sachets for high-risk procedures.

Results: Ultrasound gels from opened and unopened bottles from multiple hospital areas, including ICU and Radiology, were found to be contaminated with , with a specific batch (Brand A) linked to the outbreak. WGS analysis confirmed the genetic relatedness of clinical and environmental isolates. A hospital-wide recall of affected gel batches was implemented. Through our regional networks, notification of countries in our immediate region along with alerting our local health authorities for further investigation was also undertaken. Additionally, we continued surveillance of gels and identified further contaminated products.

Conclusions: This outbreak highlights the risks of contaminated medical products, specifically ultrasound gels. Effective environmental sampling, rapid identification, and clear communication with health authorities were key to controlling the outbreak. We have since revised our protocols to mandate the use of sterile gel for invasive procedures and continue monitoring for potential contamination in ultrasound gels.