Ice Machine Legionella and Microbiology Testing

Ice Machines as a Source for Nosocomial Infectious Diseases

Ice machines are found widespread in hospitals and nursing homes.  Because of their unique designs for freezing, storing and delivering this frozen potable water, the inherent properties of ice machines provide opportunities to introduce bacterial and fungal contamination to the water supply plumbing and ice machine surfaces, compromising the safety of the ice itself as delivered to patients and residents.  This microbial contamination can have significant infectious diseases implications for transmission of Legionella and other infectious pathogens to immunocompromised patients in these healthcare settings2-5

Comprehensive testing of ice machines for Legionella and each of the so-called CMS pathogens7 should be an essential part every healthcare Water Management Program.    

Sources of Microbial Contamination

Ice machines can be contaminated from multiple sources, including:

Incoming City Water

Ice Machines as a Source for Nosocomial Infectious DiseasesThe Big 3
  • Legionella1,2
  • Pseudomonas aeruginosa1
  • Nontuberculous mycobacteria (NTM) 1,5

Other waterborne Gram-negative bacteria 3,4

  • Acinetobacter baumannii
  • Burkholderia cepacia Complex
  • Stenotrophomonas maltophilia

Waterborne fungi: Aspergillus fumigatus6, other fungi

Hands of Ice Machine Users

  • Candida species (drug-resistant) 4
  • ESKAPE pathogens (drug-resistant)
  • Other pathogens from patients

Pathways for Ice and Ice Machine Contamination

Incoming City Water  

  • A variety of different bacteria, fungi, and protozoa (including Legionella, mycobacteria (NTM), and several gram-negative bacteria (often referred to as the CMS Pathogens), enter a building in low numbers as part of the normal microbiota in the city potable water.           

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

  • Biofilms (slime layers) form on all areas of the building premise plumbing, but especially in the ice machine plumbing as this water enters the ice machine. Bacterial growth is stimulated by heat rejected from the nearby ice machine compressor, warming the water as it sits nearby prior to entering the ice cube trays. 

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

  • Legionella and NTM replicate within amoebae in the biofilm, increasing to large numbers and getting released into the water entering the ice cube trays in high numbers prior to freezing. Extracellular gram-negative bacteria also amplify in the biofilms and get released back into the water and ice in high numbers.        

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

  • Microorganisms captured in the ice are preserved by the cold temperatures within the ice as delivered to the patients. They are revived and begin renewed replication in the patients when entering the mouth and respiratory tract.  Water collected from the ice machine waterspout will also have these same Legionella, NTM and gram-negative bacteria, although perhaps at lower levels than in the ice.
Ice Machine Legionella and Microbiology Testing

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

During operation when a medical staff member is getting ice in a container, any excess ice will hit the drain pan and splash some of the contaminated water onto the container and hands of the user, as well as on surrounding surfaces of the ice machine itself.

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

A staff member with previously contaminated hands (from another ice machine, or from contact with an infected patient), contaminates the ice machine surfaces during use.

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

Bacteria from the ice, water, container, or hands of the staff member lead to exposure and colonization of patients. An infectious disease may follow.  Transmission of a drug-resistant Acinetobacter baumannii to patients and staff within a hospital has been documented via this ice machine pathway3.

Infection Prevention Steps: Protecting Patients

Given the complexity of contamination, special attention is needed to prevent infectious disease transmission from ice machines. Recommended steps:

Ice machines have a unique complexity in terms of: 

  1. The number and types of pathogens involved.
  2. The multiple sources for microbial contamination.
  3. The multiple pathways for the contamination of both the ice and the ice machine surfaces.
  4. The different methods for transmission of these infectious pathogens to susceptible patients. As a result, ice machines require special attention for prevention of these infectious diseases. The following steps are recommended:

Install Point-of-Use 0.2 Micron Filters. Install point-of-use 0.2 micron filters on the city water line entering the ice machines.  This ensures that the water entering the ice cube freezing trays is always sterile.  Several manufacturers make filters for this purpose.

Regular Cleaning of Ice Machine Surfaces. Prepare a written schedule for frequent cleaning of the ice machine surfaces (especially the grill and drain pan) with hydrogen peroxide (or another appropriate disinfectant).

Restrict highly immunocompromised patients from any interaction with ice during their stay, unless it is made from sterile water as in #1.

Prepare a written policy for attention to handwashing/disinfection practices for medical staff before and after using an ice machine.  Use of sterile gloves is also an option for reducing this type of exposure and transmission to patients.

Perform regular testing of the bulk ice and drain pan (swab) for Legionella, NTM and P. aeruginosa (or other pathogens as needed) in order to validate steps #1 and #2 above.  This testing can be coordinated with the regular Legionella testing of the water in the facility as described in the written Water Management Program.

Ensure Ice Machine Safety in Healthcare Settings

Contaminated ice machines pose serious risks in hospitals and nursing homes. Implementing proper water filtration, strict hygiene practices, and regular microbial testing is essential to protect vulnerable patients from infections.

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References

  1. Falkinham, L.O., E.D. Hilborn, M.J. Arduino, A. Pruden, and M.A. Edwards. 2015. Epidemiology and ecology opportunistic premise plumbing pathogens: Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa. Environ. Hlth. Perspect. 123: 749-758.
  2. Graman, P.S., G.A. Quinian, and J.A. Bank. 1997. Nosocomial legionellosis traced to a contaminated ice machine. Infect. Cont. Hosp. Epidemiol. 18: 637-40.
  3. Kanwar, A., T.N. Domitrovic, S. Koganti, P. Fuldaur, J.L. Cadnum, R.A. Bonomo, and C.J. Donskey. 2017. A cold hard menace: A contaminated ice machine as a potential source for transmission of carbapenem-resistant Acinetobacter baumanniiAm. J. Infect. Control. 45: 1273-1275.
  4. Kanwar, A., J.L. Cadnum, D. Xu, A.L. Jencson and C.J. Donskey. 2018. Hiding in plain sight: Contaminated ice machines are a potential source for dissemination of Gram-negative bacteria and Candida species in healthcare facilities. Infect. Control Hosp. Epidemiol. 39: 253-258.
  5. Millar, B.C. and J.E. Moore. 2020. Hospital ice, ice machines and water as sources of nontuburculous mycobacteria: Description of qualitative risk assessment models to determine host-nontuberculous mycobacteria interplay.      Int. J. Mycobacteriol. 9: 347-362.
  6. Richardson, M. and R. Rautemaa-Richardson. 2019. Exposure to Aspergillus in home and healthcare facilities water environments: Focus on biofilms. Microorganisms. 7(1), 7;   https://doi.org/10.3390/microorganisms7010007.
  7. U.S. Department of Health & Human Services, Centers for Medicare & Medicaid Services: Survey & Certification Memorandum 17-30-Hospitals/CAHs/NHs (2017; rev. 7/6/2018).  “Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems to Prevent Cases and Outbreaks of Legionnaires’ Disease (LD)”. 

Legionella, NTM, P. aeruginosa and other gram-negative bacteria will collect in the drain pan from melted ice and increase in numbers as a replicating slime-forming biofilm.

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