Microbial Complexity of Oral Cavity of Healthy Dogs Identified by Mass Spectrometry and Next-Generation Sequencing

SIMPLE SUMMARY: The diet and contact with different environments in the practice of raising dogs contribute to a complexity of microorganism that inhabit the oral cavity of these companion animals. In addition, the close exposure of humans to pets may favor the transmission of opportunistic pathogens from dogs to owners, particularly by bite attacks, in addition to manifestations of affection such as the habit of licking the owners. Considering this scenario, we investigated the microorganisms that inhabit the oral cavities of 100 healthy dogs using a combination of traditional microbiological culture and next-generation diagnostic methods. A complexity of bacteria and fungi/yeasts was identified in the oral cavities of dogs, including agents that have been described infecting humans, such as Staphylococcus pseudintermedius and Pasteurella, Fusobacterium, and Capnocytophaga species. Furthermore, bacterial isolates with multiple resistance to antimicrobials used in human and/or animal treatment protocols were observed as well. Overall, we identified a complex microbiota inhabiting the oral cavity of healthy dogs, highlighting the risks of transmission of microorganisms from dogs to humans, especially secondary to bites, and the challenges in therapeutic approaches for humans bitten. ABSTRACT: The high complexity of the oral microbiota of healthy dogs and the close exposure of humans to companion animals represent a risk of the transmission of potential zoonotic microorganisms to humans, especially through dog bites, including multidrug-resistant ones. Nonetheless, a limited number of comprehensive studies have focused on the diversity of the microorganisms that inhabit the oral cavities of healthy dogs, particularly based on modern molecular techniques. We investigated bacterial and fungal organisms in the oral cavities of 100 healthy dogs based on a combination of conventional and selective microbiological culture, mass spectrometry (MALDI-TOF MS), and next-generation sequencing. In addition, in vitro antimicrobial susceptibility patterns of isolates and mecA resistance gene were assessed. A total of 213 bacteria and 20 fungi were isolated. Staphylococcus pseudintermedius (40/100 = 40%), α-hemolytic Streptococcus (37/100 = 37%), and Pasteurella stomatis (22/100 = 22%) were the most prevalent bacteria diagnosed by microbiological culture and MALDI-TOF MS, whereas Aspergillus (10/100 = 10%) was the most common fungi identified. Based on next-generation sequencing of selected 20 sampled dogs, Porphyromonas (32.5%), Moraxella (16.3%), Fusobacterium (12.8%), Conchiformibius (9.5%), Bergeyella (5%), Campylobacter (3.8%), and Capnocytophaga (3.4%) genera were prevalent. A high multidrug resistance rate was observed in Staphylococcus pseudintermedius isolates, particularly to azithromycin (19/19 = 100%), penicillin (15/19 = 78.9%), and sulfamethoxazole/trimethoprim (15/19 = 78.9%). In addition, the mecA resistance gene was detected in 6.1% (3/49) of coagulase-positive staphylococci. Here, we highlight the microbial complexity of the oral mucosa of healthy dogs, including potential zoonotic microorganisms and multidrug-resistant bacteria, contributing with the investigation of the microbiota and antimicrobial resistance patterns of the microorganisms that inhabit the oral cavity of healthy dogs.