Flexible endoscope:
monitoring of the final rinse-water
(Study note)

How frequently are the tests done?

  • Total viable count​ - weekly

  • Environmental Mycobacteria - quarterly

  • Pseudomonas aeruginosa - quarterly

What action can be taken if an organism identified?

Pseudomonas spp

  • Bronchoscopes, cystoscopes and ERCP: Suspend the decontamination of bronchoscopes, cystoscopes and ERCP in the EWD or affected chamber until the full identification of the Pseudomonas is known and do not decontaminate bronchoscopes/cystoscopes/ERCP in affected EWD or chamber until the water quality has been improved (some models of EWD have two sides or chambers that can be operated independently).​​

  • GI endoscope: Risk assess the continuation of GI scope decontamination.

Environmental / Non-tuberculous mycobacteria

  • Bronchoscopes, cystoscopes and ERCP: Suspend the decontamination of bronchoscopes, cystoscopes and ERCP in the affected EWD or chamber until the problem has been resolved.​

  • Review AAFB positive lavage results since previous negative mycobacterial test - look back exercise.

CFU >100cfu (repeated finding)

  • Investigate the water source;

  • Involve the EWD manufacturer to assess internal contamination and /or biofilm.

  • Suspend the use of the EWD until the problem is resolved.

What if the aerobic colony forming unit (CFU) is <100 (in 100mL​)?

CFU < 1

  • Satisfactory

  • Continue using the endoscope as normal.

1 – 9 CFU

  • Acceptable​

  • Acceptable as a one-off result.​​ The endoscopy list can continue.​​ Monitor the result.​

10 – 100 CFU

  • Unsatisfactory​

  • Take the EWD out of service pending risk assessment and investigations,​​ (It must be remembered that by default the machine will have been operating potentially for a further 5​ days since the positive sample was taken).​​

  • Test:​​
    Gram stain and oxidase test to presumptively identify Pseudomonas. Confirm identification of any oxidase positive Gram-negative organism.​​
    Send for identification if single organism presents or a significant proportion of organisms appears to be from a single species from colonial morphology.​​
    Do ZN stain for any GPB.​​
    Send these results to the Infection control team and Authorising Engineer/ Personnel (Decontamination).​​

  • An incident team may consider other risk assessment procedures to assess the risk to patients, if the EWD is to be kept in service.​​

  • Incident form (IR1)​.

  • Run additional self-disinfection cycle on the EWD, or super- chlorination, undertake remedial work on the water distribution system to investigate the problem – e.g., check the purification/filtration system and any internal components on the EWD. Instigate a re-test of the rinse water.​​

  1. If count is 10-50, and
    counts from the previous three weeks’ samples from the AER, have been below 10,
    then carry out an additional self-disinfection on the AER,
    re-test the rinse water and proceed to use the AER for all scopes.​​

  2. If the count is between 10-50, and
    a count from the previous three weeks’ samples, from the AER, have been 10 or above
    then carry out an additional self- disinfection on the AER,
    re-test the rinse water and
    do not use the AER to process bronchoscopes, cystoscopes or duodenoscopes until re-samples show acceptable counts.​​

  3. If the count is 51-100
    then carry out an additional self-disinfection on the AER,
    re-test the rinse water, and
    do not use the AER to process bronchoscopes or cystoscopies until re-tests show acceptable counts.​​

>100 CFU

  • Unacceptable​

  • EWD should be taken out of service until water quality has improved / issue resolved.

  • Test and investigate as described in Unsatisfactory/10-100 CFU section.

  • It is a requirement of BS EN ISO 15883-4:2009 that microbial contaminants of water used for final rinse applications should be maintained consistently below 10cfu/100 ml sampled when tests carried out in accordance with the BS EN ISO 15883 standard. Additionally, samples should be free of Legionella, Pseudomonas aeruginosa and Environmental mycobacteria.​

  • Multidisciplinary teams should work together to identify the source of the contamination within the final rinse supply.

  • Incident form (IR1).

Look back exercise

Depending on the identification of organism, levels and persistence of problem consideration should be given to the need for a look back exercise and/or offering antimicrobial prophylaxis to patients who have had endoscopes used in invasive procedures decontaminated in the affected EWD/chamber in the time frame between last negative rinse water test and the positive finding.​