What can we learn from the microbial ecological interactions associated with polymicrobial diseases?

ORAL MICROBIOME OF BENNETT'S (NOTAMACROPUS RUFOGRISEUS) AND YELLOW-FOOTED (PETROGALE XANTHOPUS) ROCK WALLABIES AND THE IMPACT OF INTRAORAL DISEASE

Intraoral disease, including macropod progressive periodontal disease, is one of the leading causes of morbidity and mortality for wallabies under human care. Clinical signs associated with intraoral disease vary, and diagnostic findings can be difficult to interpret without intraoral radiographs or advanced imaging; therefore, this disease process can be challenging to detect in its early stages. Previous studies have investigated the effects of intraoral disease on the normal oral microbiome of various domestic species. Results from these studies demonstrate specific changes to the oral microbiome that have the potential to be used as an early indicator of intraoral disease. The purpose of this study was to evaluate the oral microbiome of 12 Bennett's wallabies (Notamacropus rufogriseus) and 3 yellow-footed rock wallabies (Petrogale xanthopus), using next-generation sequencing, to determine if intraoral disease influences the oral microbiome, as demonstrated in other species. The study identified a total of 295 bacterial species and 388 fungal species from the oral cavity of 15 wallabies. Although not statistically significant, the results of the study suggest an increase in the number of anaerobic bacterial species in sites of disease, including Actinomyces bowdenii, a species from the family Propionibacteriaceae, Peptostreptococcus canis, Fretibacterium sp., and Synergistes jonesii. It also revealed a decrease in microbial diversity in animals with active intraoral disease compared with animals without active disease, as well as at the site of disease compared with the control site. Results from this study support the findings of similar studies assessing the oral microbiome of macropods. Additional studies are warranted to better understand the normal oral microbiome of Bennett's and yellow-footed rock wallabies and the dynamic changes in the microbiome that occur in animals with intraoral disease.

Porphyromonas spp., Fusobacterium spp., and Bacteroides spp. dominate microbiota in the course of macropod progressive periodontal disease

Macropod progressive periodontal disease (MPPD) is a necrotizing, polymicrobial, inflammatory disease commonly diagnosed in captive macropods. MPPD is characterized by gingivitis associated with dental plaque formation, which progresses to periodontitis and then to osteomyelitis of the mandible or maxilla. However, the underlying microbial causes of this disease remain poorly understood. In this study, we collected 27 oral plaque samples and associated clinical records from 22 captive Macropodidae and Potoroidae individuals that were undergoing clinical examination at Adelaide and Monarto Zoos in South Australia (15 healthy, 7 gingivitis and 5 periodontitis-osteomyelitis samples). The V3-V4 region of the 16S ribosomal RNA gene was sequenced using an Illumina Miseq to explore links between MPPD and oral bacteria in these animals. Compositional differences were detected between the microbiota of periodontitis-osteomyelitis cases compared to healthy samples (p-value with Bonferroni correction < 0.01), as well as gingivitis cases compared to healthy samples (p-value with Bonferroni correction < 0.05) using Permutational Multivariate Analysis of Variance (PERMANOVA). An overabundance of Porphyromonas, Fusobacterium, and Bacteroides taxa was also identified in animals with MPPD compared to healthy individuals using linear discriminant analysis effect size (LEfSe; p =  < 0.05). An increased abundance of Desulfomicrobium also was detected in MPPD samples (LEfSe; p < 0.05), which could potentially reflect differences in disease progression. This is the first microbiota analysis of MPPD in captive macropods, and these results support a polymicrobial pathogenesis of MPPD, suggesting that the microbial interactions underpinning MPPD may be more complex than previously documented.