The Fungus Among Us: Proactively Preventing <i>Candida auris</i> Transmission via Ultrasound Transducers

Candida auris is an emerging infectious fungus declared an urgent threat by the Centers for Disease Control and Prevention (CDC) in 2019.1 Since the CDC started tracking C. auris in 2018, they have reported a continual increase in cases.2 C. auris can be found as asymptomatic colonization on the skin or causing clinically significant infections in the blood, urine, wounds, and other body sites. In addition, there is no effective decolonization strategy for patients with C. auris on the skin and C. auris is typically resistant to one or more classes of antifungal agents, leaving patients with active infections that sometimes have limited treatment options. As the true burden of C. auris is unknown due to minimal skin colonization screening, it is crucial to ensure disinfectants used on shared medical equipment, such as surface ultrasound transducers, are effective at killing C. auris. Historically, many ultrasound transducer instructions for use (IFUs) list alcohol-free wipes, such as quaternary ammonium compound (quat), as the preferred method for low-level disinfection due to potential transducer degradation.3 Specifically, alcohol-free quat is not effective against C. auris leaving the transducers susceptible to harboring the fungus.4 As numerous manufacturers have updated their approved disinfectant lists, it is vital to convert transducers and other equipment from an alcohol-free quat to a compatible disinfectant registered to kill C. auris. Unfortunately, not all manufacturers have updated compatible disinfectant lists; therefore, it is critical to review disinfectant compatibility prior to purchasing new equipment. The United States Environmental Protection Agency (EPA) List P indicates disinfectants registered as effective against C. auris.5 The CDC notes to use disinfectants on EPA List K if List P products are not desirable.6 In response to an increase in C. auris seen at a tertiary academic medical center, the Infection Control/Hospital Epidemiology (ICHE) team reviewed locations that ordered alcohol-free quat disinfectant wipes. When communicating with departments using alcohol-free quat wipes based on purchasing data, the primary use of the wipes was to disinfect ultrasound transducers. Recognizing that the true burden of C. auris skin colonization is unknown due to lack of screening, the ICHE team identified transducers as a vulnerable source for potential C. auris transmission and reviewed all transducer IFUs used by inpatient and outpatient departments. The ICHE team chose 3 disinfectant wipes off List P and List K to check for inclusion in IFUs: sodium hypochlorite (bleach) at 1:10 dilution, quat and isopropyl alcohol, and hydrogen peroxide. Most inpatient departments converted to bleach wipes, except for procedural areas due to their preference for hydrogen peroxide wipes. Over half of the 16 outpatient departments switched to a quat and isopropyl alcohol wipe for transducers while the remaining outpatient departments moved to bleach wipes. As previously noted, not all manufacturers have updated their IFUs or a disinfectant compatibility list for their transducers. Due to the manufacturers' delay in updating the IFUs, 6 out of 65 transducers' models were not compatible with a disinfectant approved to kill C. auris. The ICHE team then performed a risk assessment for the 6 remaining models to determine which alternative product to use. The risk assessment conclusion was to prioritize patient safety by closing the gaps for potential routes of transmission, therefore allowing the remaining 6 models to move to a product that kills C. auris. Figure 1 summarizes the steps to ensure transducers are appropriately disinfected against C. auris. As C. auris prevalence increases within the United States and the true burden of colonization remains ambiguous due to lack of screening, facilities should take steps to ensure their equipment is appropriately disinfected. Alcohol-free quat is ineffective against C. auris leaving ultrasound transducers as a vulnerable source of transmission. Proactively reviewing disinfectant compatibility for ultrasound transducers, and other equipment using alcohol-free quat disinfection, is advised to inhibit the potential transmission of C. auris in all healthcare facilities [Correction added on 07 October 2024, after first online publication: The last paragraph was adjusted to make the complete sentence.].