Mitigation of microbial contamination from waste water and aerosolization by sink design

A narrative review and update on drain related outbreaks

BACKGROUND

Outbreaks linked to hospital drainage systems are well reported and continue to present challenges to incident management teams. Such outbreaks can be protracted and complex, with multi-modal strategies being required for remediation.

AIM

The aim was to summarise recent drain related outbreaks, investigate whether multimodal control measures are being implemented and determine any antecedent factors.

METHODS

Databases were searched for drain related outbreaks over a five-year period. Search terms employed included healthcare drainage outbreaks; drain outbreaks;drainage system outbreaks; sink outbreaks; shower outbreaks . Information was collected on country of origin, pathogens involved, unit affected, drain types, patient numbers, drainage system interventions, type of drain disinfectant, infection control interventions, typing method, outcomes and any antecedent factors.

FINDINGS

Nineteen drain related outbreak papers were reviewed. The majority of incidents were due to Carbapenemase producing Enterobacterales (CPE) and were from critical care settings. Most (16/19) recognised the need for a multi-modal approach. Information on the success of interventions was not documented for all but 13/19 reported no further cases after control measures. Variation in the choice of agent and frequency of application exists with regards to drain disinfection. Seven studies discussed antecedent factors.

CONCLUSION

Despite drain related outbreaks being reported for the last 24 years and review articles on the subject, outbreaks continue to pose significant challenges. There is currently no UK guidance on the management of drain related outbreaks or the design of new buildings to mitigate the risk. Addressing the challenges from hospital drainage systems should be considered a priority by agencies and guidance developers.

Controlling the hospital aquatic reservoir of multidrug-resistant organisms: a cross-sectional study followed by a nested randomized trial of sink decontamination

OBJECTIVES

The hospital water environment is an important reservoir of multidrug-resistant organisms (MDROs) and presents a risk for patient safety. We assessed the effectiveness of thermal and chemical interventions on sinks contaminated with MDRO in the hospital setting.

METHODS

We conducted a cross-sectional assessment of MDRO contamination of sinks and toilets in 26 clinical wards of a tertiary care hospital. MDRO-contaminated sink traps were then replaced and randomized (1:1:1) to receive chemical (sodium hypochlorite), thermal disinfection (steam), or no intervention. Interventions were repeated weekly for 4 weeks. Sinks were resampled 7 days after the last intervention. The primary outcome was the proportion of decontaminated sinks. MDROs of interest were extended spectrum beta-lactamase (ESBL) producing and carbapenemase-producing Enterobacterales, and non-fermentative Gram-negative bacilli.

RESULTS

In the cross-sectional assessment, at least one MDRO was identified in 258 (36%) of the 748 samples and in 91 (47%) of the 192 water sources. In total, 57 (42%) of the 137 sinks and 34 (62%) of the 55 toilets were contaminated with 137 different MDROs. The most common MDRO were ESBL Enterobacterales (69%, 95/137), followed by Verona Integron-Borne Metallo-β-Lactamase (VIM) carbapenemase producing Pseudomonas aeruginosa (9%, 12/137) and Citrobacter spp. (6%, 5/137). In the nested randomized trial, five of the 16 sinks (31%) in the chemical disinfection group were decontaminated, compared with 8 of 18 (44%) in the control group (OR 0.58; 95% CI, 0.14-2.32) and 9 of 17 (53%) in the thermal disinfection group (OR 1.40; 95% CI, 0.37-5.32).

DISCUSSION

Our study failed to demonstrate an added benefit of repeated chemical or thermal disinfection, beyond changing sink traps, in the MDRO decontamination of sinks. Routine chlorine-based disinfection of sinks may need to be reconsidered.

Antimicrobial efficacy of aqueous ozone in combination with short chain fatty acid buffers

Background

Mitigating surface contamination by microbes such as S. aureus, Salmonella enterica, or Klebsiella pneumoniae, is an ongoing problem in hospital and food production environments.

Aim

To determine whether addition of buffering solution to source water used for manufacture of aqueous ozone increases ozone efficacy against ozone-resistant bacterial species.

Methods

Antimicrobial effects of aqueous ozone were studied in combination with acetate, propionate, or butyrate short chain fatty acids (SCFA) as well as citrate or oxalate buffer formulations against Staphylococcus aureus on glass coupons. Aqueous ozone combined with an acetate buffer was also evaluated against Salmonella enterica and Klebsiella pneumoniae.

Findings

The acetate, propionate, and butyrate buffered aqueous ozone combinations had a significant 3-4 log reduction of S. aureus (P<0.05) colony forming unit (CFU), while citrate or oxalate buffered aqueous ozone, although statistically significant versus buffer alone, had less activity. Treatment of S. aureus, S. enterica, or K. pneumoniae with acetate buffered aqueous ozone also resulted in a 4 log or greater reduction in CFUs post-treatment for all three species, versus treatment with water alone.

Conclusions

All buffer systems tested had a significantly greater reduction in CFUs following treatment with the combination of buffer and ozone, compared to treatment with buffer or ozone individually, which has not been previously reported for hard surfaces. These results suggest that SCFA buffered ozone has greater anti-bacterial activity relative to either agent alone, and the activity is independent of the buffering activity. Thus, these formulations have potential to sanitize without residues, using an environmentally conscious formulation.