The arrival of Candida auris in Aotearoa NZ: risk assessment and actions needed

Candida auris is a yeast fungal pathogen that primarily causes healthcare-associated infections, particularly in intensive care units and aged residential care facilities.^{1 2} Invasive C. auris infections can result from the use of invasive medical devices that are contaminated with C. auris.^{1 2} These infections have case fatality estimates ranging from 30-70%.^3-7 As co-morbidities are common however, the mortality that is directly attributable to C. auris invasive infection is unclear.¹ Hospital outbreaks of C. auris are difficult to contain.^8-13 Most clinical isolates have some form of resistance to antifungal agents.¹⁴   

Epidemiology and impact

This pathogen was first identified in Japan in 2009 ¹⁵, and since then cases have been reported in more than 40 countries across all populated continents.^{1 16} The Centers for Disease Control (CDC) in the US recently reported a rapid rise in C. auris infections in that country.¹⁷ This included a threefold increase in infections resistant to echinocandins- the preferred antifungal drug for C. auris infection treatment.¹⁷ C. auris clinical isolates with pan-drug-resistance to the four major classes of antifungal agents have been described in the US recently.¹⁸ The COVID-19 pandemic has expanded the patient population at risk of infections caused by C. auris.^{19 20}

Risk of C. auris infection in Aotearoa NZ

The risk of C. auris infection to healthy, non-hospitalised New Zealanders is minimal as this pathogen typically only causes infections in individuals in hospitals or residential care. Following initial diagnosis, it is possible that colonisation may continue for months, including after patient discharge.^{21 22} To date, most confirmed cases of C. auris in Australian and New Zealand hospitals have had a history of overseas hospitalisation.^{23 24}  C. auris survives well in dry biofilms in the hospital environment.² See more detailed risk assessment in the Appendix.

Recommended prevention and control measures for Aotearoa New Zealand

A. Control measures aimed at detecting and managing cases
C. auris can persist on surfaces and medical equipment for several months through biofilm formation.² Standard hospital grade disinfectants are not effective at killing C. auris.²⁵ Cleaning of the environment with disinfectants with sporicidal activity (able to kill fungal and bacterial spores) is required, for example those with 0.1% sodium hydroxide and peracetic acid 2000ppm.²⁶ Updated guidelines on the disinfection of C. auris has been made available by the CDC and medical mycologists.^{25 27} We make more detailed recommendations on C. auris disinfection in the Appendix.

Recent C. auris disease control practises adopted by the CDC and Victoria Department of Health in Australia have been effective in managing C. auris infection risks.^{27 28} History of C. auris infection, locally or overseas, should be recorded upon admission of patients. We recommend screening of patients with a history of overseas hospitalisation for C. auris along with screening for other multi-drug resistant organisms (MRO). Patients with past C. auris colonisation or infection should be managed adhering to Contact Precautions; this includes placement in a single room, healthcare workers wearing appropriate personal protective equipment (PPE), dedicated patient equipment in the room, appropriate waste and linen handling and the use of disinfectants with sporicidal activity to clean surfaces in the room. In the event of a newly diagnosed C. auris case, the patient should be managed adhering to Contact Precautions as above. See discussion of population-level prevention measures below for more on the management of close contacts.

Early isolation and identification are key factors in the treatment of C. auris infections. Culture-based methods remain the main method for isolation of Candida species ^{16 29}, but may present a significant time delay (2-8 days for a result) which can impact on treatment outcomes.^30-32 However, in cases of candidaemia, C. auris can be isolated within 48-72 hours. Increasingly, more rapid biochemical, genome sequencing and mass spectrometry-based (MALDI-TOF) methods have been used to identify C. auris cases.^{16 33} Antifungal susceptibility testing should be performed on C. auris clinical isolates.²⁵ The New Zealand Microbiology Network is well placed to guide C. auris diagnostic pathways. We discuss these practices, along with other testing possibilities, in the Appendix.

B. Population-level prevention measures aimed at reducing the risk of infection

Following the detection of C. auris in 2018, the Victoria Department of Health established healthcare guidelines aimed at improving the screening and surveillance of C. auris colonisation or infection.²⁸ We recommend that the current Ministry of Health guidelines for ‘Infection Prevention and Control and management of Carbapenemase-producing Enterobacteriaceae’ (2018) be updated to include all MROs of concern, including C. auris. The principles for preventing cross-transmission of these pathogens are similar and the data collected would support a better understanding of the impact of MRO cross-transmission in healthcare settings.

We further recommend that C. auris is made a notifiable disease. 

The National Medical Warning System can be used to identify patients colonised or infected with C. auris. It allows for an alert to be placed against a patient’s national health index number indicating that they are colonised or infected with C. auris or that they have a history of sharing rooms with confirmed C. auris cases indicating that they need to be screened for this pathogen if readmitted.

The risk of introduction of C. auris into our hospitals can be reduced by risk assessing all admissions to hospital for MRO colonisation or infection.  Patients with identified risk factors, including hospitalisation overseas in the previous twelve months, should be screened for MRO colonisation or infection accordingly.

 

Author details

• Dr Françios Olivier is with the Walter and Eliza Hall Institute of Medical Research, Melbourne.
• Dr Sally Roberts and Dr Arthur Morris are from Te Whatu Ora Te Toka Tumai (Auckland District Health Board).
• Prof Kurt Krause is with the Department of Biochemistry, University of Otago, Dunedin.
• Prof Michael Baker is with the Department of Public Health, University of Otago, Wellington.

Appendix:

A. Risk assessment for C. auris

Sources of infection

C. auris survives well in the environment, unlike many other pathogenic Candida species where humans are the reservoir and are commonly colonised.² The precise environmental source of C. auris remains unknown, although investigations have uncovered isolates from the coastal wetlands of the Andaman Islands ³⁴ and commercial apples ³⁵. Genome analyses of C. auris isolates revealed that four distinct clades exist, each previously arising in four distinct geographic locations.^{36 37} There is variation in the mutations that confer antifungal resistance among these clades.³⁷

Transmissibility

High-risk patient groups for C. auris infection include those receiving immunosuppressive therapies, those recovering from invasive surgery, and those with diabetes mellitus.^{1 36} Transmission between hospitalised patients can occur though contact with a contaminated surface or object.²⁵ Transmission risk appears to be highest in healthcare settings ³⁸ and it is not clear whether community transmission of C. auris occurs.³⁹ Including C. auris in existing screening and surveillance programmes for MROs will enhance our understanding of C. auris transmission in New Zealand.

Severity

Invasive C. auris infections are normally seen in critically ill patients, for example those receiving immunosuppressive therapy or recovering from invasive surgery.¹ Resistance to antifungal drugs (in particular fluconazole and amphotericin B) is common.¹⁴ Due to lower resistance to echinocandins, these antifungal drugs have been the recommended treatment for C. auris infection.^{1 2 14} A substantial increase in resistance to this class of antifungal drug is now being reported in C. auris infections in the US.¹⁷ These infections have case fatality estimates ranging from 30-70%.^3-7

Controllability

The use of disinfectants with sporicidal activity will be critical to avoid C. auris outbreaks in New Zealand hospitals ²⁵. Considerations for hospital disinfection procedures are outlined below. Prompt implementation of Contact Precautions and placement of the patient in a single room, healthcare staff use of PPE and excellent hand hygiene will also help to contain the pathogen ²⁵.

Certainty of knowledge

Despite its recent emergence (2009) the healthcare risks of C. auris are well defined. The mode of transmission (contact with contaminated surfaces) and disinfection requirements are also well-researched. Less is known about the environmental source, or whether community transmission can occur.

Overall response strategy

C. auris is not established in Aotearoa New Zealand. Following infections in Melbourne in 2018, urgent action led to elimination of infection, and that should be the goal here. We expect that with increasing spread within overseas hospitals, as with other MROs, there is a high risk of further introductions of C. auris within New Zealand healthcare settings. C. auris infection can be eliminated through rigorous case surveillance, appropriate disinfection protocols in hospitals and ensuring that there is a rapid, yet sensitive, diagnostic pipeline.

 

B. Current strategies that are critical in the management of C. auris infection risk

Incident management

An urgent incident management response would be required if C. auris infection is diagnosed in a patient with no prior overseas hospitalisation. The coordinated incident management systems (CIMS) approach may be used to establish a cohesive strategy in minimising transmission and preventing further C. auris cases.

C. auris diagnosis

Effective C. auris isolation has been described well ^{16 25 40} and is practised by the National Mycology Laboratory at Te Toka Tumai Auckland. Antifungal resistance among C. auris clinical isolates is the norm rather than the exception.¹⁴ Antifungal susceptibility testing of all C. auris isolates, as practised by the National Mycology Laboratory, is therefore critical.

Hospital disinfection protocols

Evidence suggests that quaternary ammonia compound (QAC)-based disinfectants are not effective in disinfecting C. auris.²⁶ The use of 0.1% sodium hypochlorite or peracetic acid (PPA)-based disinfectants is strongly recommended.^{25 26} These disinfectants should be used to clean patient room surfaces twice daily, including the floor, for the duration of the patient’s stay. The use of vapourised hydrogen peroxide systems and alcohol-based disinfectants is recommended for shared medical equipment.²⁵ For guidance on contact times: the US Environmental Protection Agency has an index of disinfectants that may be used for C. auris decontamination, along with the appropriate contact time.⁴¹

Screening of patients

For patients identified on admission as high risk for MRO colonisation or infection, screening for all MROs, including C. auris, should occur. Patients transferred from overseas hospitals may be colonised or infected with several MROs. If the patient was identified as a close contact of a patient colonised or infected with C. auris in a healthcare setting, screening for C. auris alone may be performed.