environmental hygiene
By Linda Homan , RN , BSN , CIC
Healthcare Drains as a Hidden HAI Reservoir : Challenges and Prevention Strategies
Published literature reviews provide evidence that sink , shower and other wastewater drains in healthcare settings have been associated with outbreaks , particularly among the most vulnerable patient populations in neonatal and adult intensive care units , burn units , transplant units and hematology / oncology units . These outbreaks are difficult to recognize and manage because long intervals of time may pass between cases , and the number of cases at any given time is low . Once an outbreak is identified , it can be challenging to eliminate the source – bacteria growing in biofilms in drains . Previously identified methods to disinfect drains have had very limited success . 1 , 2
Waterborne bacteria are the predominant organisms found in sink-related outbreaks with the most common organism being Pseudomonas aeruginosa . Other pathogens include Enterobacteriaceae , such as Escherichia coli , Klebsiella pneumoniae , Klebsiella oxytoca , Serratia marcescens , Enterobacter species , and Citrobacter species .
Multidrug-resistant strains of these organisms are commonly found , with carbapenemases most frequently identified . Enterobacteriaceae producing extended-spectrum beta-lactamases ( ESBLs ) as well as multidrug-resistant P . aeruginosa and A . baumanii are also commonly identified .
The true burden of sink-related infections is likely underestimated as there is currently no widespread systematic strategy to identify and track this type of healthcare-associated infection ( HAI ). 3
Immunocompromised patients are most susceptible to infections with these organisms . 1 In a review of four studies , Kizny-Gordon , et al . found that risk factors for wastewater drain-associated colonization or infection are : preceding surgery , patient location , prolonged mechanical ventilation , older age , burns , longer hospital stay , and drinking tea from a contaminated dispenser . 2 Almost all identified outbreaks have occurred in intensive care units ( ICUs ) and hematology-oncology units .
Parkes , et al . reviewed the risk mitigation strategies for sink related outbreaks between 2012-2018 , discussed here . 3
● Sink and faucet configurations may contribute to the transmission . Faucets flowing directly into drains and shallow sink basins have been shown to cause splash-back . This can contaminate the hands of healthcare workers or patient care items that are stored adjacent to the sink . In addition , sinks are often used to dispose of fluids and materials other than water . These non-water substances can provide nutrients to encourage bacterial biofilm growth .
• Once an outbreak is identified , it can be challenging to eliminate the source – bacteria growing in biofilms in drains .
● Hospitals often have aging and modified water systems with uneven temperature control and dead-end pipes . Temperature fluctuations and stagnant water can contribute to bacterial growth in hospital tap water .
● Below the drain , plumbing issues may also exist , such as scale build up or p-traps and piping made of materials that encourage biofilm growth .
● Most methods to disinfect drains are not effective at killing bacteria in drains . Efforts to disinfect drains have included complete replacement of the sink or its components , installing self-cleaning traps , disinfection with processed steam , enhanced manual cleaning , descaling of pipes , and disinfection with chlorine-based solutions or other liquid disinfectants . Liquid disinfectants do not contact the surface of the drain long enough to meet the contact time needed to kill the bacteria . 4
● Existing methods to react to drain-associated outbreaks have been “ woefully ineffective ” at eliminating sink colonization . 3
Parkes , et al . suggest a more proactive approach including optimizing best practices in sink design and placement and changing healthcare worker behavior to prevent transmission :
● Correct defective conditions in water systems such as dead ends , low water-use areas , and temperature / pressure fluctuations
● Ensure that faucets don ’ t flow directly into the drain to minimize splashing / aerosolizing
● Consider changing to deeper sink basins to prevent cross-contamination of hands and adjacent surfaces
● Eliminate misuse of sinks to dispose of fluids and materials that can provide nutrition for bacterial biofilm growth
● Ensure that patient care items are not stored adjacent to sinks to avoid cross-contamination
● Ensure that p-traps and piping are made of materials that minimize biofilm growth
● Consider replacing sinks or affected components to remove the source of transmission . ( Replacing sinks may solve the problem temporarily , but eventually biofilm will grow in the new sink if other prevention measures aren ’ t taken .)
● Various methods of cleaning and disinfecting drains have been tried with mixed results . They sometimes end the outbreak but do not provide sustained decolonization of sinks .