Characterisation of aerobic gram-negative bacteria from subgingival sites of dogs – potential bite wound pathogens

Ninety-eight aerobic, gram-negative bacterial isolates from subgingival samples from family-owned dogs with naturally occurring periodontitis were characterised phenotypically by conventional biochemical testing, by cellular fatty acid profiling and by the use of commercial identification systems. The majority (48, 81%) of the fermentative isolates but only 18% of the non-fermenters were identified by conventional biochemical testing alone. With additional cellular fatty acid profiling, another 7 (12%) fermentative and 23 (59%) non-fermentative isolates were identified to genus or group level. Cellular fatty acid analysis was essential for the identification of most non-fermenters, many of which are difficult to identify due to a paucity of positive reactions in routine biochemical tests. Commercial identification systems were less useful and did not contribute to further identification of these problematic isolates. This study underlines the difficulties encountered in the identification of canine oral bacteria – a group of potential bite wound pathogens – and presents schemes for microbiology laboratories to characterise such isolates.