New Study Finds No Link Between Contaminated Endoscopes and Bloodstream Infections in 316,000+ Procedures.

A 7-year surveillance study at a 1,900-bed academic medical center in Singapore found no epidemiological association between contaminated endoscopes and postprocedural bloodstream infections (BSIs), despite routine microbiological surveillance detecting residual contamination. The findings, published May 14, 2026, in the American Journal of Infection Control, suggest that most postendoscopic BSIs are more strongly associated with procedural invasiveness and patient susceptibility than with exogenous transmission from endoscopes.

The retrospective study evaluated 316,533 endoscopic procedures performed between January 2018 and December 2024. Researchers identified 2,366 post-endoscopic BSI episodes, corresponding to an overall incidence of 7.5 per 1,000 procedures. Bronchoscopy had the highest rate at 47.7 per 1,000 procedures, followed by endoscopic retrograde cholangiopancreatography (ERCP) at 36.0 per 1,000. Lower rates were observed after gastroscopy, cystoscopy, and colonoscopy.

The investigators wrote that “higher rates were observed following bronchoscopy and ERCP, likely reflecting procedural invasiveness, mucosal disruption, concomitant infection, and underlying patient susceptibility rather than transmission attributable to endoscope-related factors.”

Routine microbiological surveillance was conducted in accordance with the Gastroenterological Society of Australia guidelines. High-risk endoscopes, including duodenoscopes, bronchoscopes, and cystoscopes, underwent monthly microbiological culture testing, while low-risk endoscopes, such as gastroscopes and colonoscopes, were cultured quarterly. During the study period, 21,899 surveillance cultures were performed, yielding 443 positive cultures.

Researchers identified species-level overlap between bloodstream isolates and surveillance cultures involving organisms such as Escherichia coli, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Candida species. However, device-level tracing found that none of the affected patients had been exposed to the implicated endoscope within the defined contamination window.

The study authors emphasized that “surveillance-detected bioburden did not translate into patient harm” and noted that “no epidemiological signal suggested exogenous transmission from contaminated endoscopes.” They added that the findings support “a low likelihood, rather than absence, of exogenous transmission under non-outbreak conditions.”

The study also highlighted how contamination detection rates increased after the institution adopted more sensitive surveillance techniques in 2023, including membrane filtration-based sampling. Annual contamination rates rose from 1.0% in 2022 to 6.1% in 2023 and 12.5% in 2024. Researchers attributed this increase to enhanced organism recovery rather than declining reprocessing performance.

Importantly, the authors argued that microbiological surveillance should be viewed primarily as a quality-assurance and system-monitoring tool rather than as a direct predictor of infection risk. “Surveillance programs are most effective when used to identify deviations in reprocessing performance, guide corrective action, and reinforce process reliability rather than serving as isolated indicators of patient harm,” the researchers wrote.

The institution has already implemented additional mitigation strategies in response to the findings. Because bronchoscopy demonstrated the highest BSI incidence, the hospital converted all 21 bronchoscopes to sterilization processing in April 2025. Researchers noted that ongoing surveillance would evaluate whether this intervention reduces BSI trends moving forward.

The authors concluded that integrating microbiological surveillance with electronic device tracking and clinical outcome monitoring creates “a robust framework for endoscope safety assurance in routine clinical practice.”