4.1.9 Incident investigation

Preparedness

The water safety group should have an agreed WSP that covers all care settings and is inclusive of a business continuity/contingency arrangement in preparation for the event that a water source, for example mains water, system water, tap water, cannot be used or an area cannot be used due to widespread known or suspected contamination. 

All high-risk settings should have a setting-specific alert organism list for clinical isolates, which should be informed by the known historical epidemiology of that setting and allow for early identification of single cases of unusual environmental organisms 

As a minimum, this alert organism list should include 

See Appendix 13 for more information on alert organisms including the locations/patient cohorts to which each apply. 

Detection of a healthcare-associated infection incident or outbreak

Colonisation or infection of gram-negative microorganisms or non-tuberculous mycobacteria, isolated from a clinical sample in any patient should raise a high degree of suspicion of a healthcare associated environmental link and should be investigated/reviewed.  

An environmental source should be considered when Enterobacteriaceae is isolated from a clinical sample and a data exceedance has been identified. 

Isolation of Legionella spp. from a clinical sample in any patient indicates transmission from the environment and should be investigated as a possible healthcare associated infection incident if the incubation period fits and there is no established link to a community source.  Further information can be found in the NIPCM A-Z of Pathogens for Legionella spp. 

When determining HAI status, the incubation period should be considered, acknowledging the wide variation (a few hours to years) for environmental organisms. 

Environmental organism outbreaks and incidents may occur over extended periods of time with significant time between cases. Consideration of an environmental link should be given to cases that have been identified over a wide time period.  

Ensure that the risk of a false negative result is considered and further sampling discussed. This can be supported by taking a measured approach to sampling from the outset.

Investigation

Water testing in response to clinical cases

The IMT should agree a water sampling plan to identify and prioritise potential sources taking account of the following: 

Water samples should be taken before disinfection of the water system or equipment or before any other remedial actions are initiated.

As a minimum, a pre-flush sample should be taken from each outlet being sampled. Post-flush samples should also be considered.

Sampling instructions can be found in SHTM 04-01 Part C 

Where no UKAS accreditation exists for specific healthcare water system-associated organisms, boards should still consider testing and can seek advice from ARHAI Scotland. See the UKAS Technical Bulletin for more information. 

Environmental surface sampling in response to clinical cases

Environmental surface sampling (swabbing) should be carried out when there is more than one working hypothesis and an environmental source is suspected.

Closing an incident

When considering whether to declare an infection incident or outbreak as ‘closed’ or ‘over’ the IMT should be assured that transmission risks have been mitigated, including exposure from any remaining colonised or infected patients and that there is a surveillance plan in place to allow for early detection of any further potentially linked cases.