16S ribosomal DNA sequence-based identification of bacteria in laboratory rodents: a practical approach in laboratory animal bacteriology diagnostics

Correct identification of bacteria is crucial for the management of rodent colonies. Some bacteria are difficult to identify phenotypically outside reference laboratories. In this study, we evaluated the utility of 16S ribosomal DNA (rDNA) sequencing as a means of identifying a collection of 30 isolates of rodent origin which are conventionally difficult to identify. Sequence analysis of the first approximate 720 to 880bp of the 5- end of 16S rDNA identified 25 isolates (83.33%) with 99% similarity to a sequence of a type strain, whereas three isolates (10%) displayed a sequence similarity 97% but <99% to the type strain sequences. These similarity scores were used to define identification to species and genus levels, respectively. Two of the 30 isolates (6.67%) displayed a sequence similarity of 95 but <97% to the reference strains and were thus allocated to a family. This technique allowed us to document the association of mice with bacteria relevant for the colonies management such as Pasteurellaceae, Bordetella hinzii or Streptococcus danieliae. In addition, human potential pathogens such as Acinetobacter spp., Ochrobactrum anthropi and Paracoccus yeei or others not yet reported in mouse bacterial species such as Leucobacter chironomi, Neisseria perflava and Pantoea dispersa were observed. In conclusion, the sequence analysis of 16S rDNA proved to be a useful diagnostic tool, with higher performance characteristics than the classical phenotypic methods, for identification of laboratory animal bacteria. For the first time this method allowed us to document the association of certain bacterial species with the laboratory mouse.