Zoe Marshall-Jones

The Canine Oral Microbiome

Determining the bacterial composition of the canine oral microbiome is of interest for two primary reasons. First, while the human oral microbiome has been well studied using molecular techniques, the oral microbiomes of other mammals have not been studied in equal depth using culture independent methods. This study allows a comparison of the number of bacterial taxa, based on 16S rRNA-gene sequence comparison, shared between humans and dogs, two divergent mammalian species. Second, canine oral bacteria are of interest to veterinary and human medical communities for understanding their roles in health and infectious diseases. The bacteria involved are mostly unnamed and not linked by 16S rRNA-gene sequence identity to a taxonomic scheme. This manuscript describes the analysis of 5,958 16S rRNA-gene sequences from 65 clone libraries. Full length 16S rRNA reference sequences have been obtained for 353 canine bacterial taxa, which were placed in 14 bacterial phyla, 23 classes, 37 orders, 66 families, and 148 genera. Eighty percent of the taxa are currently unnamed. The bacterial taxa identified in dogs are markedly different from those of humans with only 16.4% of oral taxa are shared between dogs and humans based on a 98.5% 16S rRNA sequence similarity cutoff. This indicates that there is a large divergence in the bacteria comprising the oral microbiomes of divergent mammalian species. The historic practice of identifying animal associated bacteria based on phenotypic similarities to human bacteria is generally invalid. This report describes the diversity of the canine oral microbiome and provides a provisional 16S rRNA based taxonomic scheme for naming and identifying unnamed canine bacterial taxa.

Antimicrobial activity observed among cultured marine epiphytic bacteria reflects their potential as a source of new drugs

The surfaces of marine eukaryotes provide a unique habitat for colonizing microorganisms where competition between members of these communities and chemically mediated interactions with their host are thought to influence both microbial diversity and function. For example, it is believed that marine eukaryotes may use their surface-associated bacteria to produce bioactive compounds in defence against competition and to protect the host against further colonization. With the increasing need for novel drug discovery, marine epibiotic bacteria may thus represent a largely underexplored source of new antimicrobial compounds. In the current study, 325 bacterial isolates were obtained from the surfaces of marine algae Delisea pulchra and Ulva australis. Thirty-nine showed to have antimicrobial activity and were identified via 16S rRNA gene sequencing. The majority of those isolates belonged to Alpha- and Gammaproteobacteria. Interestingly, the most commonly isolated bacterial strain, Microbulbifer sp., from the surface of D. pulchra has previously been described as an ecologically significant epibiont of different marine eukaryotes. Other antimicrobial isolates obtained in this study belonged to the phyla Actinobacteria, Firmicutes and Bacteroidetes. Phylogenetically, little overlap was observed among the bacteria obtained from surfaces of D. pulchra and U. australis. The high abundance of cultured isolates that produce antimicrobials suggest that culturing remains a powerful resource for exploring novel bioactives of bacterial origin.

Assessment of dental plaque coverage by Quantitative Light-induced Fluorescence (QLF) in domestic short-haired cats

Dietary means of reducing plaque and calculus deposits are frequently sought for the maintenance of oral health in cats and dogs. In the development of such products sensitive, reliable, reproducible methods of measuring plaque and calculus are key. The aim of this study was to assess Quantitative Light-induced Fluorescence (QLF™) for the detection of dental plaque coverage in cats compared to the modified Logan and Boyce technique. The techniques were utilised in a crossover study, which compared two diets for their effect on plaque deposition in a cohort of 24 adult cats. Analysis of the effect of diet on plaque coverage by both the modified Logan and Boyce technique and QLF showed a significant effect of feeding regime (p=0.024 and p≤0.0001, respectively) with good agreement between the techniques in the percentage reduction of plaque accumulation. A within study assessment of QLF demonstrated excellent intra-operator repeatability (coefficient of variation 2.2%). Similarly, inter-operator reproducibility was also good (coefficient of variation 2.3%). A retrospective analysis, using the data to estimate the sample size required for at least 90% power to detect a 15% difference between treatments in a two-way crossover study, established that 10 cats would be sufficient for plaque measurement by QLF, while assessment by the modified Logan and Boyce method required over 30 cats. QLF was determined to be a reliable, reproducible method for the assessment of plaque deposition in cats and requires fewer subjects for the detection of differences between treatment effects compared to the modified Logan and Boyce method.

Canine and Feline Microbiomes

There is an increasing appreciation for the importance of the symbiotic relationship between microbes and their mammalian hosts in modulating companion animal health and nutrition. Indeed, the colonisation dynamics and influence of microorganisms inhabiting such body systems as the gastrointestinal tract (from mouth to anus) show many similarities between dogs and cats and their human counterparts. However, given the evolutionary divergence of these host species, as well as inherent differences in their diet and lifestyle, disparities in both the microbial communities and their impact on host health do exist. These differences are perhaps best exemplified in the oral cavity where microbial communities, host physiology and dietary influences result in differences in disease prevalence and phenotypic characteristics. Companion animals such as dogs and cats rarely experience dental caries which are commonly found in humans. However, periodontal disease, a destructive inflammation of the gums and periodontal soft tissues which is modulated by the microbiota, has an alarming prevalence within both the dog and cat population. Similarly, within the gastrointestinal tract, asymptomatic colonisation of dogs and cats by species known to be pathogenic within the human host is widely reported. This highlights the need to better understand these host microbial interactions in species-specific models.