Medscape Medical News
Diana Phillips
October 08, 2014

An outbreak of an unusual form of Carbapenem-resistant enterobacteriaceae (CRE) in an Illinois hospital has been linked to duodenoscopes contaminated with the bacteria despite no apparent lapses in disinfection protocol, according to a study by researchers from the Centers for Disease Control and Prevention (CDC).

From January 2013 through December 2013, 39 patients at a tertiary care hospital in northeastern Illinois tested positive forEscherichia coli producing the New Delhi metallo-B-lactamase (NDM), a strain that has been infrequently observed in the United States.

Of those patients, 35 had undergone gastrointestinal endoscopy via duodenoscope at the hospital, report Lauren Epstein, MD, from the Division of Healthcare Quality Promotion, CDC, Atlanta, Georgia, and colleagues in an article published in the October 8 issue of JAMA.

“NDM-producing CRE have the potential to add substantially to the total CRE burden,” the authors write. CRE outbreaks present a public health concern because of the limited treatment options available and the risk for death associated with invasive infections.

After the identification of initial patients through clinical cultures, the investigators conducted a case-control study to identify risk factors for NDM-producing CRE carriage. They also assessed infection control practices and obtained environmental cultures from duodenoscopes, the endoscopy reprocessing area, and procedure rooms, according to the report.

For the case-control study, 27 control subjects were randomly selected from patients in the hospital’s inpatient rehabilitation ward who had negative CRE rectal screening cultures. Case patients included those identified during the initial field investigation who were treated at the hospital.

“On bivariable analysis, case status was significantly associated with history of [endoscopic retrograde cholangiopancreatography], magnetic resonance cholangiopancreatography, and antibiotic use in the past 3 months,” the authors write.

During the environmental investigation, the researchers recovered NDM-producing E coli from one of the hospital’s reprocessed duodenoscopes. The recovered strain shared more than 92% similarity to the isolates of all of the case patients.

On the basis of this association, the investigators focused their infection-prevention assessment on the hospital’s duodenoscope reprocessing practices and identified no breaches in disinfecting protocols based on manufacturer recommendations.

The NDM-producing E coli was recovered from the terminal portion of the reprocessed duodenoscope nearly 2 months after its last use, according to the authors. The terminal portion is the area around the scope’s enclosed elevator mechanism, which has a separate channel and provides orientation of catheters, guide wires, and accessories into the endoscopic visual field. “The complicated design of duodenoscopes makes cleaning difficult. It appears that these devices have the potential to remain contaminated with pathogenic bacteria even after recommended reprocessing is performed.”

A possible option for ensuring the absence of residual contamination on these devices would be to test for it during reprocessing. “Many international professional societies recommend periodic microbiological surveillance testing of duodenoscopes after full reprocessing,” the authors note.

In an accompanying editorial, William A. Rutala, PhD, MPH, and David J. Weber, MD, MPH, from Hospital Epidemiology, University of North Carolina Health Care, and the Division of Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, call on clinicians to report and publish cases of infectious diseases related to endoscopy, particularly when reprocessing protocols have been followed, to determine whether the current report represents “the tip of the iceberg,” or whether it is an isolated occurrence. “If endoscopes are found to be contaminated with potential pathogens (eg, enteric gram-negative bacilli), the clinical effects of such contamination need to be quantified,” they stress.

“The key concern raised by this study is whether current US endoscope reprocessing guidelines are adequate to ensure a patient-safe gastrointestinal endoscope (one devoid of potential pathogens) or if endoscopes with their long, narrow channels, right-angle turns, difficult to clean and disinfect components, and heavy microbial contamination [are] impossible to reliably high-level disinfect,” the editorialists write.