Canine oral biofilms: cultural, molecular, and in vitro studies

The canine oral microbiota is poorly understood compared to that of humans. The aim of this work was to improve understanding of the canine oral microbiota. This was achieved by surveying the canine oral microbiota, determining coaggregation interactions between its mem­ bers, and developing a laboratory microcosm. Bacteria were isolated from the dental plaque and saliva of dogs, and isolates were identified by comparative 16S rRNA gene sequenc­ ing. From 339 isolates, 84 phylotypes belonging to 37 genera were identified. Approximately half were identified to species level, and 28 % of these were also members of the human oral microbiota. Thirty eight phylotypes were tentatively identified as candidate new species. The genera most frequently isolated from saliva were Actinomyces, Streptococcus, and Granulicatella. Porphyromonas, Actinomyces, and Neisseria were most frequently isolated from plaque. On average, se­ quences from this study differed by almost 7 % in the 16S rRNA gene compared to similar organisms from humans. Targeted PCR was used to detect culture resistant bacteria from ca­ nine plaque. Successful amplification indicated that Spirochaetes and candidate division TM7 bacteria were present, however the identities of the originating organisms were not determined. The entire cultivable plaque microbiota from a single dog was as­ sessed for coaggregation reactions. Eight (6.7 %) unique interactions were detected from 120 crosses, indicating that the prevalence of coag­ gregation is similar in the canine and human oral microbiotas. Genera common to both hosts generally exhibited similar coaggregation reac­ tions, however autoaggregation was more common among bacteria iso­ lated from dogs. The constant depth film fermenter was used to grow microcosms from canine plaque and saliva using a mucin containing artificial saliva supplemented with horse serum as the growth medium. The model produced biofilms similar to natural dental plaque, which could be used to investigate the canine oral microbiota further.