Candidozyma / Candida auris

Associated infections

• Candidaemia and invasive bloodstream infection
• Intravascular catheter-related infection
• Wound and surgical site infection
• Urinary tract infection, typically catheter-associated
• Intra-abdominal infection
• Otitis and external ear infection
• Asymptomatic skin, axillary and groin colonisation
• Osteomyelitis and device-associated bone and joint infection, reported less commonly
• Ventricular assist device and other implanted-device infection

Transmission route

Transmission is predominantly contact-mediated. Colonised patients shed the yeast from skin into the immediate environment, contaminating bed rails, bedside tables, mobile medical equipment and surfaces at a distance from the patient such as windowsills. The US Centers for Disease Control and Prevention notes that the organism can persist on surfaces for weeks to months and that it is not reliably inactivated by some disinfectants in common healthcare use; products relying solely on quaternary ammonium compounds are specifically identified as ineffective, and CDC recommends an EPA-registered product with a claim against Clostridioides difficile spores (List K) or a product with a specific C. auris claim. Dry-surface biofilm formation contributes to this tolerance. Practical control therefore rests on single-room isolation with contact precautions, hand hygiene, dedicated or rigorously decontaminated shared equipment, and validated terminal cleaning.

Shared mobile equipment deserves particular emphasis, because it is the vector most often implicated in onward spread once a colonised patient is present. Blood pressure cuffs, thermometers, pulse oximetry probes, ultrasound probes and their gel bottles, mobile radiography units, patient lifting equipment and physiotherapy aids all move between patients and are all cleaned less consistently than fixed surfaces. Multi-bed bays, high patient turnover and reliance on agency staff unfamiliar with local protocols compound the problem. Intensive care and high-dependency units are consistently over-represented in reported clusters, reflecting the combination of device density, prolonged length of stay and heavy contact with staff hands.

Candidozyma auris is not a recognised organism of building water distribution systems, and there is no established reservoir in treated or purified water loops. It is nevertheless directly relevant to reprocessing because it contaminates equipment surfaces and because its environmental hardiness means that a contaminated endoscope, accessory, transport tray or drying cabinet may act as a vehicle between patients. Recovery of this organism from any reprocessing-associated sample, including final rinse water, should be treated as a critical finding: it most plausibly reflects contamination from a colonised patient or from the clinical environment rather than a water-quality failure, and it warrants immediate laboratory confirmation, quarantine of the implicated equipment, review of the full reprocessing pathway and notification of the facility infection-prevention service and the relevant state public health unit.

Relevance in endoscopy and reprocessing

The correct framing for endoscopy and sterilising services is that Candidozyma auris is a surface and equipment problem, not a water-loop problem. There is no evidence that it colonises treated water distribution systems, reverse-osmosis loops or washer-disinfector water circuits, and it is not among the organisms that final rinse water monitoring is designed to detect. What it does do is contaminate everything a colonised patient touches, including the exterior of a scope, the trolley it was transported on, the transport container, the bench in the decontamination room and the hands of the person who handled it. The exposure of interest is therefore the dirty-side environment and the clean-side surfaces that dirty-side contamination can reach.

Against high-level disinfection the organism behaves as a vegetative yeast and is inactivated by the agents used in endoscope reprocessing when they are delivered at the specified concentration, temperature and contact time; thermal disinfection in a washer-disinfector is likewise effective. The difficulty is not the disinfection step but everything around it. Dry-surface biofilm renders the organism substantially more tolerant of the environmental disinfectants used for wiping down benches, trolleys and cabinets, and quaternary ammonium products, which are widely used for exactly this purpose in reprocessing rooms, are specifically noted as unreliable. A facility can therefore run a fully compliant disinfection cycle and still recirculate the organism through its own room-cleaning practice.

The operational implications follow directly. Facilities should confirm that the environmental disinfectant used in decontamination areas, on transport trolleys and inside storage cabinets carries an appropriate claim rather than relying on a quaternary ammonium product; should ensure that scopes and accessories used on known or suspected colonised patients are transported in closed containers and handled with contact precautions on the dirty side; should schedule such patients where practicable at the end of a list to allow terminal cleaning; and should ensure storage cabinets, which are shared, warm and infrequently cleaned, are included in the cleaning schedule with a suitable product. Drying and storage matter here for a different reason than with water-associated organisms: the concern is not that residual moisture supports growth in the channel but that a contaminated cabinet interior recontaminates the exterior of an otherwise correctly reprocessed device.

Interpreting a detection

Any detection of Candidozyma auris in a reprocessing-associated sample is a critical result and is handled differently from every other organism in this reference. The first step is confirmation, not action on the preliminary report, because misidentification runs in both directions: older biochemical platforms commonly report this species as Candida haemulonii, Candida famata, Rhodotorula glutinis, Saccharomyces cerevisiae or similar, and conversely a laboratory alert to a presumptive auris result may on definitive testing prove to be another species. Confirmation requires MALDI-TOF with a current database or a molecular method, and the reporting laboratory should be contacted directly rather than waiting for a routine report cycle. Confirmation must not delay precautionary containment: implicated equipment should be quarantined while the identification is being resolved.

When interpreting a positive, the plausibility assessment points away from water. A genuine detection is far more likely to indicate contamination from a colonised patient or from the clinical environment, transferred by hands, equipment or the sampling process itself, than to indicate anything about the water plant. The first checks are accordingly clinical and environmental: whether any patient recently on the list is known or suspected to be colonised, whether any patient has a history of overseas hospitalisation or transfer from a facility with known cases, whether the sample was taken in a room where a colonised patient had been managed, and whether the sampler had prior contact with the clinical environment. Sampling technique and container handling should be reviewed as for any organism, but a handling explanation does not downgrade the response, because handling contamination with this organism is itself evidence that the organism is present in the facility.

Escalation is immediate and does not wait for a repeat sample or a trend. A single confirmed isolate warrants notification of the facility infection-prevention service, the water safety or reprocessing governance group, and the relevant state or territory public health unit, because C. auris is subject to enhanced surveillance and public health follow-up in Australian jurisdictions. The subsequent review should cover the full reprocessing pathway rather than the water system alone: transport and handling, dirty-side environmental cleaning products and practice, the cleaning schedule for trolleys and storage cabinets, staff hand hygiene and glove practice, and whether any patient on recent lists requires screening. Patient screening decisions and any look-back exercise sit with infection prevention and the public health unit, not with the water-quality provider, and the facility should be advised accordingly.

Antimicrobial resistance

Antifungal resistance is a defining feature of the species. A high proportion of isolates worldwide are resistant to fluconazole, and resistance to amphotericin B is reported in a substantial minority. Echinocandin resistance remains less common but is increasing, and isolates resistant to all three principal antifungal classes have been described. Because susceptibility cannot be predicted from identification alone, antifungal susceptibility testing is required on every clinical isolate, and empirical therapy for suspected invasive infection is generally echinocandin-based pending results. Resistance is compounded by tolerance to several environmental disinfectants, so antifungal resistance and environmental persistence must be managed as a single problem rather than as separate issues.

The mechanisms are broadly those recognised in other yeasts but occur at unusually high frequency. Azole resistance is associated with point mutations in the ERG11 gene and with overexpression of efflux transporters; echinocandin resistance is associated with FKS1 hot-spot mutations and, importantly, can emerge during treatment, so a patient failing echinocandin therapy warrants repeat isolation and repeat susceptibility testing rather than an assumption that the original result still applies. Resistance profiles differ between the recognised clades, so published proportions from one region do not transfer reliably to another and local laboratory data should be used where available.

For infection control the more consequential resistance is chemical rather than antifungal. The organism forms dry-surface biofilm on hospital surfaces, which raises the concentration and contact time needed for inactivation well above that required for planktonic cells and above what a routine wipe-down delivers. Quaternary ammonium compounds are specifically identified as unreliable, and products should instead carry a sporicidal or specific C. auris claim. Chlorine-based agents at appropriate concentration, hydrogen peroxide formulations and peracetic acid are the practical options. Ultraviolet and hydrogen peroxide vapour systems have a place as adjuncts to terminal cleaning but not as substitutes for physical cleaning, since organic soil protects the organism from both. The essential point for a reprocessing facility is that a compliant high-level disinfection cycle kills this organism, while a routine bench wipe with the wrong product may not, and both steps have to be right.