Study links hospital Candida auris outbreak to reusable thermometers

A large Candida auris outbreak at a hospital in England appears to be linked to reusable patient-monitoring equipment, a team of researchers reports today in the New England Journal of Medicine.

The outbreak in the neurosciences intensive care unit (ICU) at Oxford University Hospitals involved 70 patients who were infected or colonized with C auris, a fungus that has become increasingly resistant to azoles, echinocandins, and polyenes—the three classes of antifungals used to treat infections caused by Candida and other fungal species.

An epidemiologic investigation and case-control study by investigators from the University of Oxford, Public Health England, and elsewhere found that the most compelling explanation for the prolonged outbreak was the persistence of the organism on reusable skin-surface axillary probes, a device placed in a patient's armpit for continuous temperature monitoring.

"Our results indicate that reusable patient equipment may serve as a source of healthcare-associated outbreaks of infection with C. auris," the authors of the study write.

C auris was first identified in Japan in 2009 and since then has emerged as a significant healthcare-associated pathogen in several countries, causing hospital outbreaks on five continents. The multidrug-resistant fungus can cause severe infections in immunocompromised patients and has been associated with high mortality.

To date, UK hospitals have reported more than 200 cases of C auris colonization or infection, with three large hospital outbreaks recorded. Although the precise mode of transmission has not yet been identified, C auris has shown an ability to persist on hospital surfaces and instruments and spread between patients, which has spurred UK health officials to update infection prevention and control procedures.

Recurrence a known problem, but extent unclear

After an initial investigation identified four patients who were colonized and five patients who were infected with C auris from Feb 2, 2015, through Oct 16, 2016, the hospital introduced a routine screening program to prospectively identify the organism in patients and high-touch areas. The investigators focused on all patients identified from Feb 2, 2015, through Aug 31, 2017, then conducted a case-control study to determine risk factors for colonization and infection.

Of the 70 patients found to be colonized or infected with C auris, 66 (94%) had been admitted to the neurosciences ICU before diagnosis. Seven of the patients developed invasive C auris infections. No deaths were directly attributable to infection. Most patients were colonized for 2 to 3 months.

When the 70 C auris patients were compared with 361 control patients who had also been in the neurosciences ICU but had not become colonized or infected, and factors like length or stay in the ICU and patient vital signs were controlled for, the investigators found that the use of axillary temperature probes increased the risk of infection nearly seven times (multivariable odds ratio [OR], 6.80).

The temperature probes, which were a part of routine care for patients who received mechanical ventilation or were undergoing temperature monitoring for neuroprotective management, were used in 57 case patients (86%) and 122 control patients (34%). Systematic fluconazole was also associated with an increased risk (OR, 10.3), but only 3 case patients (5%) received antifungal treatment before colonization or infection.

Meanwhile, analysis of 128 environmental samples obtained in November 2016, February 2017, and April 2017 found C auris only rarely in the general hospital environment or the air. However, C auris isolates were identified on axillary temperature probes, and whole-genome sequencing of those isolates revealed that they were genetically similar to some of the patient isolates. In addition, the armpit was often the first spot to be colonized in case patients.

Finally, although the hospital had implemented recommended measures to prevent and control the spread of C auris, including patient contact isolation and enhanced cleaning with chlorine-based products, the outbreak wasn't brought under control until the axillary temperature probes were removed from use in the neurosciences ICU on Apr 24, 2017. After that, only four more cases were identified.

"This probably in part reflects the survival of this organism in the hospital environment, particularly on plastic and moist surfaces," the authors write.

The authors also note that while the temperature probes were cleaned between patients with wipes containing quaternary ammonium compound, they are difficult to clean, and recent studies have shown that quaternary ammonium compounds have poor activity against Candida species.

See also:

Oct 3 N Engl J Med study

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