Candida auris detected in the oral cavity of a dog in Kansas

ABSTRACT Candida auris is an emerging human fungal pathogen, first described in Japan in 2009, and first detected in the United States in 2016. Here, we report the first-ever description of C. auris colonizing a human pet, the first identification of C. auris in a non-human mammal in the United States and the first C. auris isolate from the state of Kansas. While analyzing the oral mycobiome of dogs from a shelter in Kansas, the oral swab from one dog was found to contain C. auris as well as three other fungal species. The presence of C. auris in a dog suggests the possibility of zoonotic transmission to humans. The isolate is a member of Clade IV, which has been found in patients in Chicago and Florida, while Clades I and III are the most prevalent in the United States. The isolate is resistant to fluconazole, terbinafine, and amphotericin B but susceptible to caspofungin, consistent with the drug-resistant characteristics of many human C. auris isolates. The source of C. auris transient colonization in this dog is unknown, and there is no evidence that it was further transmitted to humans, other dogs in the shelter, or pets in its adopted household. Isolation of C. auris from a dog in Kansas has public health implications as a potential emerging source for the zoonotic spread of this pathogenic fungus, and for the development of antifungal resistance. IMPORTANCE Candida auris is an emerging fungal infection of humans and is particularly problematic because it is multi-drug resistant and difficult to treat. It is also known to be spread from person to person by contact and can remain on surfaces for long periods of time. In this report, a dog in a shelter in Kansas is found to be colonized with Candida auris. This is the first study to document the presence of Candida auris on a pet, the first to document C. auris presence on a non-human mammal in the United States, and the first to report an isolate of C. auris within the state of Kansas. The presence of C. auris in a pet dog raises the possibility of zoonotic transmission from pets to human or vice versa.

in dogs, we were interested in the use of azole antifungals to inhibit cytochrome P450 liver enzymes (9).These antifungals may alter the susceptibility profile of the dog oral mycobiome.As a control, we surveyed the susceptibility profile of the dog mycobiome (10).
With University of Missouri-Kansas City (UMKC) IACUC approval and concurrence by Kansas State University (KSU) IACUC, oral swabs were obtained from 251 local shelter dogs from February 2021 to September 2022.Swabs were struck on CHROMA gar Candida solid media (11) that differentiates between fungal species and contains chloramphenicol to select against bacterial growth.Colonies with unique color or morphology were restruck.DNA was prepared from the isolates (12), and the rDNA internally transcribed space (ITS) of each isolate was amplified by PCR (13).Each PCR product was sequenced (University of Missouri-Columbia Genomics Technology Core, Columbia, MO).The resulting sequences were analyzed by NCBI BLAST (14) to identify the species of the isolate.The isolates were analyzed for Minimum Inhibitory Concentra tions (MIC) by standard Clinical and Laboratory Standards Institute and Etest protocols (15,16).
Whole-genome sequence (WGS) of the C. auris isolate was conducted at the U.S. Centers for Disease Control and Prevention (CDC), Mycotic Diseases Branch (MDB).DNA was extracted using the Quick-DNA (ZR) Fungal/Bacterial Miniprep Kit (Zymo Research, Irvine, CA, USA).Genomic libraries were constructed using Illumina DNA Prep kit (Illumina, Inc., San Diego, CA, USA) and sequenced on Illumina Nova-Seq using NovaSeq 6000SP reagent kit (500 Cycles).Reads were submitted to the Sequence Read Archive (SRA) database from the National Center for Biotechnology Information (NCBI), BioProject accession PRJNA999713.A random set of 109 C. auris sequences representing different clades were included in the genomic analysis for comparison to the isolate.SNPs were identified using MycoSNP v1.4 as described by Bagal et al. (17).Analyses were conducted using C. auris strain B11205 [GenBank Accession no.GCA-016772135.1].Genetic distance calculations and neighbor-joining tree construction were performed using MEGA 11.The consensus topology, branch support, and maps were visualized using Microreact [http://microreact.org].
Of 251 dogs analyzed, 73 dogs contained fungal species.One dog, a 2-year-old female Retriever mix (Dog A) was found to contain four fungal species, including Malassezia pachydermatis, C. albicans, C. glabrata, and C. auris.The dog was swabbed within 1 week of entering the shelter; thus the C. auris isolate may have originated in the previous home before she was surrendered to the shelter.The C. auris isolate was analyzed at the CDC, where it was confirmed to be C. auris and was identified as a member of Clade IV, a clade which has been found in the United States in infections in Chicago and in Florida (Fig. 1).Most U.S. isolates are either Clade I or Clade III (18,19).Based on phylogenetic analysis, the genetic distance between the dog's isolate and other Clade IV isolates was greater than 90 single-nucleotide polymorphisms, suggesting significant evolutionary distance.
Regarding the history of Dog A, her previous owner purchased her and her littermate at 8-week-old, kept them for nearly 2 years, and surrendered the dog and her littermate due to allergies.No one in that household was immunocompromised.Dog A was not a therapy dog, did not have a history of visiting health care facilities, had no previous medical issues, and had no travel outside of the Kansas county of residence.When Dog A was swabbed, there was no evidence of fungal disease on physical exam, and no known history of antifungal administration.Dog A's male littermate, Dog B, was surrendered from the same household, was housed in a separate kennel in the shelter, and was swabbed on the same day.Dog B had no detectable fungal disease, was not receiving any current medication, and had no record of antifungal use.Dog B had two fungal species in its oral mycobiome: Malassezia pachydermatis and Candida parapsilosis, but no detectable C. auris.
Dog A was adopted from the shelter in May 2021 (soon after the swab was obtained).She is now an indoor dog, with no medical history other than a brief respiratory illness where she received antibiotics.Her current owners adopted another dog, a Beagle puppy, Dog C, in 2022.This dog has no medical concerns.The owners of Dogs A and C are not immunocompromised and do not report illness.Dogs A and C were swabbed in May 2023 and no evidence of C. auris was found in oral or ear swabs of either dog.In the May 2023 swab, Dog A did have two fungal species detected in the mouth: Malassezia pachydermatis and Naganishia diffluens.In summary, Dog A was colonized with C. auris in May 2021 and was not colonized with C. auris in May 2023.This suggests that the sampling for C. auris was near the limit of sensitivity and was not sufficiently sensitive to regularly detect an ongoing low-level fungal colonization.Alternately the colonization may have been cleared in the 2-year interval.
The C. auris isolate was obtained from Dog A on 25 May 2021.Thirty isolates were obtained from other dogs in the shelter before that date and 54 isolates were obtained after that date.Only a single swab was taken from each dog.No other dogs were found to be orally colonized with C. auris, and no shelter personnel were diagnosed with a C. auris infection although these personnel were not orally swabbed.This suggests that the equipment and environment at the shelter did not contribute to oral spreading of C. auris between dogs or to humans.
Increasing temperatures have the potential to select for environmental fungi, such as C. auris, that have adapted for growth at temperatures of the human body (22).Interesting, identifying C. auris in a dog that have average body temperatures of 38.3-38.7 ( 23) is more evidence of increased C. auris thermotolerance.
The presence of C. auris in the oral mycobiome of a dog is the first report of C. auris in Kansas (24), which to date has not reported human infection or colonization.The identification of this C. auris isolate in a dog raises the possibility of zoonotic transmission of C. auris, and documents that the fungus is present in Kansas as a potential reservoir despite not having caused human disease.
Although C. auris can cause either colonization or clinical illness, veterinary and human healthcare professionals should be alert for additional cases of C. auris and work with their state public health department and the CDC to confirm infection and development of an appropriate public health response.

FIG 1
FIG 1 Neighbor-Joining phylogenetic tree of C. auris isolates.Square colors represent the different C. auris clades.Branch lengths represent single nucleotide polymorphisms.The C. auris isolate from the dog in Kansas is starred (B24973).The 109 random isolates are being used in a collaboration with the CDC and the White laboratory.