Use of synthetic oligonucleotide DNA probes for the identification of different strains of Fusobacterium nucleatum

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Abstract
The ability of three different oligonucleotide probes to identify different oral strains of Fusobacterium nucleatum was tested. Probes 119 and 214 were designed on the basis of known amino acid sequences from the N-terminal end of an outer membrane protein of F. nucleatum strain Fev1. Probe H 2.1, was a randomly cloned chromosomal DNA fragment of 2.1 kbp. The specificities of the probes were examined by testing each of them against a panel of five other species of Fusobacterium (six strains), oral and non-oral, and also against seven different oral species of six other genera. The chromosomal DNA of the bacteria to be examined was digested to completion using the restriction enzymes HincII, HindIII, EcoRI, EcoRV and Sau3AI. Digests were run on agarose gels and subjected to southern blotting before being hybridized with the probe in question. The results were confirmed by running a slot blot of genomic DNA from all of the 19 strains and hybridizing with a probe H 2.1. Probe H 2.1 turned out to be the most specific and useful of the three probes investigated. By use of this probe, interstrain identification of the six different strains of F. nucleatum could be performed and the strains could be distinguished from other oral species found in the oral cavity, such as Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Capnocytophaga sputigena, Porphyromonas (Bacteroides) gingivalis, Eikenella corrodens and Leptotrichia buccalis. The probe reacted weakly with other non-oral species of the genus Fusobacterium, and there was no problem in distinguishing between the different strains.