We have been posting for a while about the emerging recognition of CPE contamination of drains in clinical settings, which seems to be fueling some CPE transmission. Until now, there’s been plenty of publications identifying the problem, but very few presenting a solution. In fact, attempts to tackle CPE contamination of drains have had moderate impact, at best. A new short study in ICHE illustrates the potential of a foaming hydrogen-peroxide based disinfectant to tackle contamination with resistant Gram-negative bacteria in drains.

The study was performed in a 26-bed ICU in the US, with a history of CPE issues. Each room had a bed, toilet, and two sinks (one at room entry and one next to the toilet). (Quite why a patient in the ICU should need a toilet is beyond me – but I guess it means that a patient can be stepped down from intensive care in the ICU.) Interestingly, the hospital used a peroxygen disinfectant (hydrogen peroxide / peracetic acid combo) for routine daily cleaning/disinfection. Patients were assigned to treatment of the sinks next to the toilet with a hydrogen peroxide disinfectant delivered via a foaming machine (yep, think foam party from uni / college days!), treatment with sodium hypochlorite solution, or no treatment. The sink drains were treated once and sampled prior to treatment, on the day of disinfection, and 7 days later. Swabs were processed to culture Gram-negative bacteria.

Baseline CFU counts in the three groups were not significantly different. There was a significant reduction in CFU count in the sinks treated with the foaming disinfectant but not in the sinks treated using chlorine on day 1. By day 7, there was again no significant differences in the CFU count for the three groups.

A few reflections:

• The microbiology methods used did not specifically identify CPE amongst the diverse group of Gram-negative bacteria cultured. And the results were not stratified by genus or species. So, it’s possible that the significant reduction associated with the foaming disinfectant could have been driven by environmental Gram-negative bacteria of little clinical consequence.
• This was not a comparison of a foaming disinfectant vs. a non-foaming disinfectant because the disinfectant chemicals were different. It would be interesting to see a study comparing the impact of a foaming and non-foaming version of the same disinfectant.
• This study doesn’t help us much in determining a ‘treatment’ strategy – although suggests that treatment will have to be regular (more than weekly) to maintain an impact.
• We need to keep more than half and eye on material compatibility. If a chemical treatment is effective in the short term but damages pipework, this could cause even bigger issues in the medium to long term (in terms of plumbing issues or in terms of creating an even bigger biofilm monster).
• We also need to keep more than half an eye on staff exposure issues when we embark upon creating foaming disinfectants. In this study, the authors found that EVS staff reported no odour during the foaming process – but hydrogen peroxide is almost completely odourless, so we need to think carefully about how we assure staff safety during this sort of process (probably by using a combination of electronic ‘sniffers’ and PPE).
• The peroxygen chemicals (hydrogen peroxide and peracetic acid) seem like the best candidates as a basis for a foaming drain-biofilm-busting disinfectant because they’re fast acting, environmental friendly, and have the almost unique property of tackling both micro-organisms in a biofilm and the biofilm matrix itself (whereas most disinfectants only tackle the micro-organisms in the biofilm). Sodium hypochlorite also shares the property with the peroxygens of tackling both the micro-organisms in the biofilm and the biofilm matrix itself, but is not a good candidate for foaming because of occupational exposure issues.

This is an extremely helpful piece of hypothesis generating work, which gives me some hope that there’s a light at the end of the drainpipe for tackling CPE contamination of drains.