Another guest post from Dr Phil Norville (bio below)…

Very few weeks go by without me reading a paper discussing a multidrug-resistant outbreak that is linked to contaminated water or wastewater systems. The most recent was an outbreak of Achromobacter species in 22 patients which was linked to water in contaminated tubes of a medical pressurizer (used for urology surgery). It was one the reasons Jon and I wrote a letter to the Journal of Hospital Infection calling for a move towards the standardisation of wastewater sampling.

As we discuss in the letter, there are variations in how, when, where and at what frequency wastewater systems are sampled. Frequently, these systems are only sampled as part of an investigation to determine the root cause of an outbreak. Given the risk that wastewater systems pose to patients, healthcare organisations should consider sampling and monitoring wastewater systems regularly. To do so, there is a need to standardise the methodology used.

Let’s put this into perspective and imagine a sink in an intensive care unit which is potentially linked to an MDRO outbreak. There are many different factors to think about when considering how the sink should be sampled.  

• Which part of the sink do we sample? The trap, the plughole, pipes or the basin?
• Who carries out the sampling? Normally this would fall into the remit of the microbiology department but what about healthcare organisations who might outsource microbiology services?
• What method do we use for sampling? Given that conventional microbiological methods may not give the full picture of the contamination, do we consider molecular methods which can provide greater accuracy on the different species present. What about the cost associated with molecular methods and ultimately who pays for it?
• How do we interpret the results from the sampling? If the sink returns a positive for outbreak organism, what do we do next? What about significant molecular findings that are not matched by culture? How do we decontaminate the sink and ultimately how do we assess the impact of that intervention? Clearly cessation of the outbreak is one measure, but can we be confident we have eradicated the outbreak organism in this sink to ensure the outbreak doesn’t happen again?

Given all these considerations, it is necessary to standardise the sampling of wastewater systems. A reproducible and standardised method will enable wastewater systems to be sampled with consistency and results interpreted with confidence which could support continuous monitoring of wastewater systems. It would also allow the impact of interventions (such as decontamination) to be assessed more easily and allow those conducting research to read across data between from other studies more easily, supporting comparative evaluation.

Standardisation of sampling methodology will be difficult and will require input from microbiology, infection prevention and control teams, engineers, and estates departments.  Given that the risk of infection from wastewater systems tends to be higher in higher risk patient groups (intensive care or high dependency for example), there may be a benefit to implementing routine analysis in these departments, increasing awareness of risks and subsequently protection for some of our most vulnerable patients. This standardisation could also be applied to the detection of antimicrobial resistance (AMR) genes. Hospital wastewater systems have been shown to have a high prevalence of AMR genes and monitoring and surveillance of AMR genes could be beneficial to identify risk and support the fight against AMR.

Read the paper here: Norville P, Otter JA. The requirement to move towards standardisation of wastewater sampling. J Hosp Infect. Published online April 27, 2024. doi:10.1016/j.jhin.2024.04.006

References

Tian J, Zhao T, Tu R, et al. Achromobacter species (sp.) outbreak caused by hospital equipment containing contaminated water: risk factors for infection. J Hosp Infect. 2024;146:141-147. doi:10.1016/j.jhin.2024.02.002

Butler J, Upton M. What’s really down the hospital plughole?. J Hosp Infect. 2023;138:92-93. doi:10.1016/j.jhin.2023.04.005

Kelly SA, O’Connell NH, Thompson TP, et al. Large-scale characterization of hospital wastewater system microbiomes and clinical isolates from infected patients: profiling of multi-drug-resistant microbial species. J Hosp Infect. 2023;141:152-166. doi:10.1016/j.jhin.2023.09.001

Bio

Dr Phil Norville has a PhD in Microbiology and a Masters in Infection Prevention and Control. He worked for 12 years at one of the world’s leading IPC companies, most recently as Clinical and Scientific Director until April 2024 when he started his own independent IPC consultancy, NORVATE Consulting.