Quality control in colorectal cancer screening: Systematic microbiological investigation of endoscopes used in the NORCCAP (Norwegian Colorectal Cancer Prevention) trial

Background: Endoscopic colorectal cancer (CRC) screening is currently implemented in many countries. Since endoscopes cannot be sterilised, the transmission of infectious agents through endoscopes has been a matter of concern. We report on a continuous quality control programme in a large-scale randomised controlled trial on flexible sigmoidoscopy screening of an average-risk population. Continuously, throughout a two-year screening period, series of microbiological samples were taken from cleaned ready-to-use endoscopes and cultured for bacterial growth. Results: 8573 endoscopies were performed during the trial period. Altogether, 178 microbiological samples (2%) were taken from the biopsy channels and surfaces from the endoscopes. One sample (0.5%) showed faecal contamination (Enterobacter cloacae), and 25 samples (14%) showed growth of environmental bacteria. Conclusions: Growth of bacteria occurs in a clinical significant number of samples from ready-to-use endoscopes. Pathogenic bacteria, however, were found only in one sample. Improvement of equipment design and cleaning procedures are desirable and continuous microbiological surveillance of endoscopes used in CRC screening is recommended.