Prevention Challenges

Contaminated Rinse Water Causes Pseudo-Outbreak in China

37 patients tested positive for P. aeruginosa in the Shanghai hospital, according to the study.

This list of culprits responsible for bronchoscope contamination seems never-ending.

A January 2020 study traced a 2016 pseudo-outbreak of Pseudomonas aeruginosa in bronchoscopy patients at a 2,100-bed facility in Shanghai back to contaminated rinse water used in the manual cleaning of flexible bronchoscopes.

Between May and September 2016, 37 patients tested positive for P. aeruginosa in the Shanghai hospital, according to the study. Once the rinse water had been properly filtered and sterilized, infection control personnel subsequently had to replace all faucets, drainpipes, and connecting tubes to eliminate the antimicrobial-resistant bacterium, which researchers believed was surviving in biofilm in those structures.

Pseudo-outbreaks refer to situations where a rise in positive cultures is observed but there is no evidence of patient disease. P. aeruginosa is the most common bacterium found on contaminated flexible endoscopes and the most common strain of Pseudomonas to infect people, according to the CDC.

The pseudo-outbreak described in the 2020 study was documented after facility staff found P. aeruginosa in bronchoalveolar lavage (BAL) samples from 37 patients in a five-month period of 2016. The study, “Bronchoscope-related Pseudomonas aeruginosa pseudo-outbreak attributed to contaminated rinse water” was published in the American Journal of Infection Control and conducted by Yajun Zhang, Haijian Zhou, Qianqian Jiang, Qin Wang, Shan Li, and Yi Huang.

BAL is commonly used to diagnose lung disease. The process involves squirting fluid into a small part of the lung and then collecting the fluid with a flexible bronchoscope for examination. To avoid contaminating samples during collection and prior to analysis, a closed-loop sampling system may be used.

In the 2016 Shanghai case, contaminated bronchoscopes caused the BAL samples to be tainted. Upon further investigation, researchers found the bronchoscopes had been contaminated by nonsterile rinse water used in manual cleaning.

Bronchoscopes disinfected with an automated endoscope reprocessor or flushed with an alcohol solution after the final rinse did not tarnish BAL samples during the five-month period, according to the study. Only those bronchoscopes that were manually cleaned from start to finish harbored the infectious agent.

Like all reusable flexible endoscopes, bronchoscopes are difficult to reprocess between uses because of their long narrow channels. Though they are the least complex of flexible endoscopes – only one channel as compared with, for example, three channels and an elevator mechanism on a duodenoscope – errors in reprocessing flexible bronchoscopes still occur.

Inadequate reprocessing results from human error, contaminated cleaning instruments, inability to remove biofilm, improper drying and storage, or because an endoscope has been broken or compromised.

Other studies have traced pseudo-outbreaks of P. aeruginosa back to nonsterile ice that was mixed with sterile saline for BAL, a common practice to reduce the risk of bleeding. Two ice machines in UNC Health Care systemhospitals tested positive for M. mucogenicum in 2017. This pseudo-outbreak affected 15 patients.

Reducing the risk to patients from flexible endoscopes is not easy, as there are many factors that may contribute to the contamination of these medical devices. One way to greatly decrease any potential of device-related infection from cross-contamination is to use single-use flexible bronchoscopes.

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