Contaminated duodenoscopes triggered a 2013 outbreak of a rare strain of Escherichia coli infections at a single hospital in northeastern Illinois, according to a report published online Oct. 7 in JAMA.
Unlike previous clusters of bacterial transmission related to these devices, this one could not be attributed to lapses in infection-control practices, defects in the duodenoscopes, or device malfunction. Instead, the carbapenem-resistant bacteria in this outbreak — NDM-producing (New Delhi metallo-beta-lactamase) E. coli — were recovered from the enclosed elevator channel of side-viewing duodenoscopes that had been cleaned, maintained, and used according to manufacturer’s instructions. “It appears that these devices have the potential to remain contaminated with pathogenic bacteria even after the recommended reprocessing is performed,” said Dr. Lauren Epstein of the division of healthcare quality promotion, Centers for Disease Control and Prevention, and her associates.
“Facilities should be aware of the potential for transmission of antimicrobial-resistant organisms via this route and should conduct regular reviews of their duodenoscope reprocessing procedures to ensure optimal manual cleaning and disinfection,” they noted.
The outbreak was discovered by a laboratory that routinely screens carbapenem-resistant Enterobacteriaceae isolates for NDM production and notifies the CDC of positive results, to ensure quick control of these dangerous organisms. The first case was identified from results of a urine culture, and six more patients who had been treated at the same hospital during a 4-month period also were found to have positive clinical cultures. Screening cultures were then performed on these patients’ roommates and on ward mates of the index case, turning up another two cases of carbapenem-resistant NDM-producing E. coli infection.
A review of the medical records showed that six of these patients had undergone endoscopic retrograde cholangiopancreatography (ERCP) at this hospital. The facility then notified all 226 patients who had undergone a procedure with any of the hospital’s three duodenoscopes during the preceding 9 months of their potential exposure, and offered them testing and treatment. A total of 27 additional cases were found, plus 1 additional case in the roommate of a patient who had been transferred to a long-term care facility.
In all, 35 of the 39 cases in this outbreak had been exposed to the hospital’s duodenoscopes.
A case-control analysis involving nine case patients and 27 control subjects who had been hospitalized during the study period showed that the infection was indeed strongly related to ERCP. Environmental cultures were collected from numerous areas of the hospital, and the only positive results were obtained from the elevator channels of two duodenoscopes. But no breaches were found in the reprocessing of the equipment.
Nevertheless, the hospital switched from automated high-level disinfection of the devices using an enzymatic cleaner to gas sterilization using ethylene oxide. Subsequent culturing showed no further contamination of the equipment, and no further cases of infection have occurred, the investigators said (JAMA 2014 [doi:10.1001/jama.2014.12720]).
Endoscopic facilities typically use high-level disinfection, as opposed to sterilization, for duodenoscopes. Although the switch to sterilization at this hospital may have been instrumental in containing the outbreak, the evidence from this single incident is not compelling enough to recommend that all such facilities make this change. Moreover, sterilization’s long processing and aeration time, the toxicity of some sterilizing agents to staff and patients, and its incompatibility with some devices make widespread adoption unlikely, Dr. Epstein and her associates said.
Unlike other endoscopes, duodenoscopes have an elevator channel “that allows for the use and manipulation of a guide wire. At the terminal end of the elevator channel is a mechanical piece containing a cantilevered elevator mechanism; the intricate design surrounding the elevator mechanism makes accessing all surfaces during manual cleaning difficult,” they noted.