The mycobiome of the oral cavity in healthy dogs and dogs with periodontal disease

Gastrointestinal colonization by Diutina (Candida) rugosa in a 6-year-old Siberian Husky

A 6-year-old 21.5 kg castrated male Siberian Husky was presented for acute onset of lethargy, vomiting, hemorrhagic diarrhea, and inappetence. Physical examination revealed marked discomfort upon abdominal palpation and 5%-7% dehydration. The CBC and biochemical profile revealed changes consistent with mild to moderate inflammation, dehydration, and gastrointestinal (GI) disease. Despite aggressive gastrointestinal support, anorexia persisted, and an upper GI endoscopy was performed in conjunction with esophagostomy tube placement. Endoscopy revealed abnormal gastric mucosa characterized by moderately well-demarcated areas of blue-black discoloration. Impression smears of a gastric biopsy revealed abundant extracellular yeasts with morphology most consistent with Candida spp. and frequent extracellular cocci. Similar yeast and bacteria, in lower numbers, were observed on cytologic analysis of a direct smear of the rectal mucosa. A rectal swab submitted for fungal culture yielded pure growth of fungal yeasts identified as Diutina (formerly Candida) rugosa by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. The dog's clinical signs improved with fluconazole, and he was discharged. Follow-up fungal culture of a rectal swab showed no growth of D. rugosa. To the authors' knowledge, this is the first case report that describes the clinical, hematologic, cytologic, and gross findings of enteric colonization by D. rugosa in a dog.

Longitudinal Analysis of Canine Oral Microbiome Using Whole Genome Sequencing in Aging Companion Dogs

Aged companion dogs have a high prevalence of periodontal disease and canine cognitive dysfunction syndrome (CCDS) and the two disorders are correlated. Similarly, periodontal disease and Alzheimer's Disease are correlated in people. However, little is known about the oral microbiota of aging dogs. The goal of this project was to characterize the longitudinal changes in oral microbiota in aged dogs. Oral swabs were taken from ten senior client-owned dogs on 2-3 occasions spanning 24 months and they underwent whole genome shotgun (WGS) sequencing. Cognitive status was established at each sampling time. A statistically significant increase in alpha diversity for bacterial and fungal species was observed between the first and last study visits. Bacteroidetes and proteobacteria were the most abundant bacterial phyla. Porphyromonas gulae was the most abundant bacterial species (11.6% of total reads). The species Lactobacillus gasseri had a statistically significant increase in relative abundance with age whereas Leptotrichia sp. oral taxon 212 had a statistically significant positive longitudinal association with cognition score. There is an increased fungal and bacterial alpha diversity in aging dogs over time and nearly universal oral dysbiosis. The role of the oral microbiota, particularly Leptotrichia and P. gulae and P. gingivalis, in aging and CCDS warrants further investigation.

Fungal diversity and drug susceptibility of the oral mycobiome of domestic dogs

The purpose of this study was to characterize the variety and diversity of the oral mycobiome of domestic dogs and to identify the commensal and potentially pathogenic fungi present. Two hundred fifty-one buccal swabs from domestic dogs were obtained and struck onto a chromogenic fungal growth medium that distinguishes between fungal species based on colony color and morphology. After isolating and harvesting single colonies, genomic DNA was extracted from pure cultures. PCR was used to amplify a fungal-specific variable rDNA region of the genome, which was then sent for sequencing. Sequencing results were input into the NCBI BLAST database to identify individual components of the oral mycobiome of tested dogs. Of the 251 dogs swabbed, 73 had cultivable fungi present and 10 dogs had multiple fungal species isolated. Although the dogs did not show signs of oral infections at the time, we did find fungal species that cause pathogenicity in animals and humans. Among fungal isolates, Malassezia pachydermatis and species from the genus Candida were predominant. Following fungal isolate identification, antifungal drug susceptibility tests were performed on each isolate toward the medically important antifungal drugs including fluconazole, ketoconazole, and terbinafine. Drug susceptibility test results indicated that a large number of isolates had high MIC values for all three drugs. Exploring the oral mycobiome of dogs, as well as the corresponding drug susceptibility profiles, can have important implications for canine dental hygiene, health, and medical treatment. Identifying the microorganisms within the canine mouth can illustrate a common pathway for fungal pathogens of One Health concern to spread from our canine companions to humans.

Functional biomes beyond the bacteriome in the oral ecosystem

Selective constraint and pressures upon the host tissues often signifies a beneficial microbiome in any species. In the context of oral microbiome this displays a healthy microbial cosmos resisting the colonization and helps in rendering protection. This review highlights the endeavors of the oral microbiome beyond the bacteriome encompassing virome, mycobiome, protozoa and archaeomes in maintaining the oral homeostasis in health and disease. Scientific data based on the peer-reviewed publications on the microbial communities of the oral microbiome were selected and collated from the scientific database collection sites of web of science (WOS), pubmed central, Inspec etc., from 2010 to 2021 using the search key words like oral microbiome, oral microbiota, oral virome, oral bacteriome, oral mycobiome and oral archaeome. Data excluded were from conference proceedings, abstracts and book chapters. The oral homeostasis in both the health and disease conditions, mostly is balanced by the unrevealed virome, mycobiome, oral protozoa and archaeome. The review documents the need to comprehend the diversity that prevails among the kingdoms in order to determine the specific role played by each domain. Oral microbiome is also a novel research arena to develop drug and targeted therapies to treat various oro-dental infections.

Malassezia: Zoonotic Implications, Parallels and Differences in Colonization and Disease in Humans and Animals

Malassezia spp. are commensals of the skin, oral/sinonasal cavity, lower respiratory and gastrointestinal tract. Eighteen species have been recovered from humans, other mammals and birds. They can also be isolated from diverse environments, suggesting an evolutionary trajectory of adaption from an ecological niche in plants and soil to the mucocutaneous ecosystem of warm-blooded vertebrates. In humans, dogs and cats, Malassezia-associated dermatological conditions share some commonalities. Otomycosis is common in companion animals but is rare in humans. Systemic infections, which are increasingly reported in humans, have yet to be recognized in animals. Malassezia species have also been identified as pathogenetic contributors to some chronic human diseases. While Malassezia species are host-adapted, some species are zoophilic and can cause fungemia, with outbreaks in neonatal intensive care wards associated with temporary colonization of healthcare worker’s hands from contact with their pets. Although standardization is lacking, susceptibility testing is usually performed using a modified broth microdilution method. Antifungal susceptibility can vary depending on Malassezia species, body location, infection type, disease duration, presence of co-morbidities and immunosuppression. Antifungal resistance mechanisms include biofilm formation, mutations or overexpression of ERG11, overexpression of efflux pumps and gene rearrangements or overexpression in chromosome 4.

Treatment of Naturally Occurring Periodontitis in Dogs With a New Bio-Absorbable Regenerative Matrix

Although periodontal disease is one of the most common (oral) diseases in dogs, an effective treatment approach to periodontitis lacks. The aim of this study was to evaluate the safety and efficacy of a regenerative, bio-absorbable implant biomaterial made of medical-grade porcine gelatin, which is cross-linked by transglutaminase into a porous scaffold for the treatment of periodontitis in dogs in a clinical setting. Nine client-owned dogs were included in this multicenter, prospective interventional clinical study. A split-mouth design was used to treat any teeth with periodontitis; teeth on one side of the mouth were treated with open periodontal therapy alone (control teeth) and teeth on the other side were treated with open periodontal therapy and the tested implant (teeth treated with the implant). A recheck under general anesthesia was performed 3 months after the initial treatment and included periodontal probing, dental radiographs, and/or cone-beam computed tomography (CBCT) of the teeth included in the study. This revealed a reduction of the probing depth (PD) at all teeth, but in teeth treated with the implant, a statistically significant improvement (average 2.0 mm) over control teeth (average 1.0 mm) was diagnosed. Similarly, alveolar bone height was increased at most of the teeth, but in teeth treated with the implant, a statistically significant improvement (average 1.26 mm palatally and 1.51 mm buccally) over control teeth (average 0.58 mm palatally and 0.7 mm buccally) was observed for the buccal site. Open periodontal therapy alone improves clinical parameters and alveolar bone height in dogs with periodontitis, which is further significantly improved by the addition of the implant used.