Outbreak Tracker
Outbreak Tracker
August 02, 2019
2 min read

WGS surveillance detects VRE outbreak linked to IV contrast

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact customerservice@slackinc.com.

Lee H. Harrison, MD
Lee H. Harrison

Whole-genome sequencing, or WGS, surveillance identified an outbreak of vancomycin-resistant Enterococcus faecium infections that was linked to nonsterile preparation of injectable contrast medium for interventional radiology procedures, researchers reported in Clinical Infectious Diseases.

“This investigation demonstrates that WGS surveillance can uncover novel transmission pathways that can be used to inform [infection prevention] practice,” Lee H. Harrison, MD, professor of medicine and epidemiology at the University of Pittsburgh, told Infectious Disease News.

In a related editorial, Mary K. Hayden, MD, professor and chief of the division of infectious diseases at Rush University Medical Center in Chicago, explained how WGS “has emerged as the gold standard method for microbial subtyping and as a powerful tool for nosocomial outbreak investigations” due to its “superior discriminatory power, ie, the capacity to distinguish genetically similar from unrelated strains; ability to detect antibiotic resistance and virulence genes; and potential to delineate chains of transmission in addition to infection clusters.”

“Coupled with traditional epidemiological investigation, WGS has revealed sources and routes of transmission that would otherwise have remained hidden,” she wrote.

Harrison and colleagues analyzed WGS surveillance data from November 2016 to November 2017 at University of Pittsburgh Medical Center-Presbyterian Hospital and discovered a cluster of 10 genetically related vancomycin-resistant enterococci (VRE) infections.

“WGS surveillance can detect outbreaks that go unnoticed by traditional hospital epidemiologic methods,” Harrison said. “The outbreak we describe in our paper was not detected because VRE is a common hospital pathogen and therefore the outbreak did not substantially increase our VRE infection rate, and the 10 patients were housed on eight different nursing units in our hospital, so nothing unusual was noticed by health care personnel working on those units.”

An EHR review identified interventional radiology (IR) as a potential transmission route, and an outbreak investigation was initiated, including a matched case-control study, Harrison and colleagues explained.

According to the study, nine of the 10 patients had undergone an IR procedure with IV contrast within 22 days before infection onset. In the matched case-control study, the researchers observed an association between VRE infection and preceding IR procedure (matched OR [MOR] = 16.72; 95% CI, 2.01-138.73) and IR procedure with contrast (MOR = 39.35; 95% CI, 7.85-infinity).

A review of IR practices and the manufacturer’s training video revealed sterility breaches in contrast preparation, according to Harrison and colleagues. Additionally, the investigation uncovered a possible transmission from an IR technician.


“There are virtually no data on the risk of infection after IR procedures. Since there is some infection risk inherent in any invasive procedure, this very strongly suggests that this is an understudied area of hospital epidemiology,” Harrison said.

Infection prevention interventions prevented any further IR-associated VRE transmissions, the researchers reported.

Hayden noted that, while WGS surveillance identified the outbreak, practices were still necessary to uncover the errors in practice and “implement changes to prevent future infections.”

“The study by Sundermann [and colleagues] is a welcome addition to the growing literature on the value of WGS for genomic surveillance of nosocomial pathogens,” Hayden wrote. “Wider uptake of this approach will require demonstration of cost-effectiveness and actionable turnaround times, as well as development of robust, flexible, and automated tools for analysis of sequence data.” – by Marley Ghizzone

Disclosures: The authors report no relevant financial disclosures.