C auris Outbreak Tied to Skin Surface Temperature Probe

Janis C. Kelly

October 04, 2018

A new piece of the Candida auris puzzle was put into place when a prolonged outbreak of multidrug-resistant C auris in a neurosciences intensive care unit in Britain was traced to contaminated reusable skin surface axillary temperature probes.

David W. Eyre, DPhil, and colleagues from Oxford University Hospitals NHS Foundation Trust, report the details of the outbreak and how it was brought under control in an article published online October 3 in the New England Journal of Medicine.

Their analysis confirms that environmental transmission plays a role in C auris outbreaks. Such transmission had been suspected after a large outbreak in New York, but prior investigations could not rule out patient-to-patient transmission as this one has.

Eyre and colleagues identified 70 patients in the unit who were colonized or infected with C auris between February 2015 and August 2017. The unit includes an open ward of 13 beds plus 3 single rooms, and sees about 650 admissions per year. Most patients had primary diagnoses of trauma or intracranial bleeding. Median age was 52 years.

A multivariable analysis that controlled for length of stay, patient vital signs, and patient laboratory results identified two predictors for acquiring C auris in the unit: use of reusable skin surface axillary temperature probes (adjusted odds ratio, 6.80) and systemic fluconazole exposure (adjusted odds ratio, 10.34). Only 3 of the 70 patients had received prior fluconazole, however.

The authors explain that continuous temperature monitoring using reusable skin surface axillary probes is part of routine care for patients receiving mechanical ventilation and for patients being monitored for neuroprotection management.

To counter the ongoing outbreak, a patient and environmental screening program was implemented in October 2016. Eyre and colleagues analyzed more than 9000 screening swabs from 900 patients, which represented 2872 unique patient-days of screening. Of those, 9.3% of swabs in 62 unique patients yielded C auris isolates, indicating a rate of 2.9 cases per 100 neurosciences intensive care unit in-patient days before intervention. There were no deaths attributable to C auris.

Analysis of C auris isolated from colonized patients and from infected patients showed high levels of resistance to fluconazole (100%), voriconazole (98%), and posaconazole (90%), as well as 18% resistance to amphotericin. Genetic analysis showed that the outbreak sequences formed a single genetic cluster within the South African clade of C auris; the researchers estimate that this subclade emerged in April 2013.

Infection control interventions instituted to curtail the outbreak included patient contact isolation and enhanced cleaning with chlorine-based products. "In addition, we implemented 'decluttering' to facilitate cleaning, reduced bedside equipment, and removed fans and forced-air convection blankets. Despite these intensive measures, the outbreak was prolonged," Eyre and colleagues write.

Only after routine use of skin surface temperature axillary probes was discontinued on April 11, 2017, did the incidence of new C auris colonization and infection decrease. An unplanned rechallenge event occurred when a senior nurse went on leave and use of the axillary probes was resumed, after which the incidence of new infections increased until the probes were withdrawn again on April 24, 2017.

The probes had been cleaned between patients with wipes containing quaternary ammonium compound, with no additional disinfection step. The authors explain that this was "the accepted custom and practice but differed from the manufacturer's instructions for use."

The manufacturer's recommendation includes cleaning with a soft cloth moistened with 70% isopropanol, activated dialdehyde (Cidex), or sodium hypochlorite (1 part bleach diluted with 10 parts water minimum), followed by disinfection by immersing the probe into the same cleaning solution for up to 2 minutes. However, the authors comment, "The probe manufacturer (Philips Medical Systems) does not make any claim as to the efficacy of the chemical cleaning set out for the purposes of infection control, and recommends the institution's infection control disinfection policies be consulted."

According to Centers for Disease Control and Prevention guidance, quaternary ammonium compounds routinely used in healthcare settings are not sufficient to remove C auris and should be replaced with cleaning products from the US Environmental Protection Agency list that have been approved as effective against Clostridium difficile spores.

The structure of the skin surface probes also presents some mechanical barriers to cleaning with wipes because of "a two-layer rubber sheath protecting the distal end of the wire adjacent to the sensor," the authors write.

In 2016, the neurosciences intensive care unit also instituted routine use of single-dose micafungin prophylaxis for surgical procedures in all patients colonized with C auris, and the authors report that no invasive infections have occurred since then.

However, Eyre and colleagues note that even after removal of the temperature probes from routine use, C auris was not completely eliminated, which they attribute in part to the organism's ability to survive on plastic and moist surfaces. They conclude that survival in the environment appeared to facilitate persistence and transmission, and warn that "reusable patient equipment may serve as a source of health care–associated outbreaks of infection with C. auris."

One coauthor reports support from Gilead Sciences Inc. outside the submitted work. The other authors have disclosed no relevant financial relationships.

N Engl J Med. 2018;379:1322-1331. Abstract

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