By Carol A. Kemper, MD, FACP

Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center

Dr. Kemper reports no financial relationships relevant to this field of study.

SOURCE: Kanwar A, et al. 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 2018; Jan. 31: doi: 10.1017/ice.2017.321. [Epub ahead of print].

Kanwar et al conducted a point prevalence survey of all ice machines in five different hospitals and two nursing homes in their area. Protocols for cleaning and disinfecting machines on either a weekly or monthly basis were in place at each facility, although none of the facilities performed surveillance cultures or molecular methods to monitor cleaning. First, machines were inspected visually for debris, and swab cultures were obtained from both the ice and water chutes. Water samples of 100 mL were collected for culture. Swabs for culture were obtained from 64 machines (3-16 samples per facility).

Visual inspection revealed that 98% of machines contained stagnant water in the pan; 38% contained melting ice in the pan, 34% contained dripping water, even when the water spout was not in use, and 27% exhibited visible water sprayed on the surrounding countertops or floor. Many of the machines showed visible soiling, food, or slime layers.

Gram-negative bacilli and/or Candida organisms were cultured from 100% of the drain pans, 72% of the pan grills, and 52% of the chutes. Swab cultures from 94% of the pans yielded > 100 colonies of gram-negative bacilli, including Enterobacteriaceae (60%), Pseudomonas spp. (26%), Serratia spp. (6%), Stenotrophomonas maltophilia (4%), and Acinetobacter spp. (3%). Of these, 7.7% were carbapenem resistant. All cultures of water and ice were negative. Five of the machines were tested again following cleaning and disinfection with a hydrogen peroxide disinfectant, and all cultures were negative.

Hospital staff were observed using the ice machine on 20 occasions. Staff touched the ice and/or water spouts in nine of 20 episodes, and falling ice touched hands (as it fell into the pan) in 10 of 20 episodes. Cultures of hands frequently yielded gram negatives and yeast. This study provides a plausible explanation for contamination of ice machines in hospital units. Even if machines are cleaned and disinfected successfully on a regular basis, they may become contaminated quickly by the hands of staff, touching either spouts or falling ice, with contamination of biofilm. Two quick remedies may be to require staff to cleanse their hands with alcohol hand gel prior to using an ice machine, and to direct housekeeping personnel to perform more frequent machine cleaning. Improvement in the design for these machines also may help. For example, deeper pans may help reduce splashes and sprays of water, and different types of spouts or chutes that cannot be touched readily by personnel would reduce cross-contamination.