Although the anaerobic, non-sporulating, pointed bacilli of the mouth, which are now grouped in the genus Fusiformis, have been cultivated since 1898 (Veillon and Zuber), much confusion still exists concerning their properties and relationships. The literature dealing with this group of bacteria is large, but it consists mainly of efforts to establish their pathological significance on the basis of occurrence. Only a few systematic studies have been attempted, and the findings of these investigations have been contradictory. Krumwiede and Pratt (1913) divided 15 strains of Fusiformis into 2 classes by means of the fermentation of sucrose. Knorr (1922) created 3 morphological groups on the basis of his study of 4 strains. He employed Fusobacterium as the generic name. This classification was used later in "Determinative Bacteriology" by Lehmann-Neumann-Breed (1931). Varney (1927) divided 18 strains into 4 types and 2 subtypes on morphological and serological grounds. Pratt (1927), repeating her earlier work, found 2 morphological groups and concluded that serological procedures had little value in the classification of Fusiformis. As a result of his investigations, Smith (1932) was led to accept 3 morphological types. Bibby and Knighton (1933) reached the same conclusions. Like Pratt, they were unsuccessful in their attempts to employ serological methods. The most extensive study of Fusiformis was made by Slanetz and Rettger (1933). They studied 53 strains isolated from many sources and were Rockefeller Fellow in Dentistry.
The use of carbamide (synthetic urea) in a mouth rinse has been suggested because in the mouth the carbamide is converted into ammonium carbonate which acts as an efficient buffer for acids. The combination of carbamide and quinine has been recommended as an antiseptic for oral use; the alkalinity resulting from the conversion of carbamide makes the quinine much more germicidal (2). Other therapeutic properties of carbamide such as ability to increase capillary proliferation, stimulate tissue granulations and dissolve necrotic tissue are probably of minor importance in the use of carbamide as an oral rinse.Carbamide is converted into ammonium carbonate by heat or by the action of an enzyme called urease, which is found in saliva in minute quantities and also is produced by many species of proteolytic bacteria. No investigations of the urease-producing bacteria of the mouth could be found in the literature, so this study was undertaken to determine their incidence in the oral flora.Shulte and Thompson (3) studied the urea-splitting bacteria in urine and found potent urea-splitting organisms as part of the normal urethral flora in fifteen of two hundred cases. They also found such bacteria associated with renal calculae of the calcium carbonate and calcium phosphate type, and believed the presence of these bacteria predisposed to severe infection. To prevent and treat such infections, these men used a weak lactic acid solution (0.25 to .5%). Proteus ammoniae, Proteus morganie, Micrococcus ureae, certain strains of Staphylococcus aureus and certain strains of diphtheroids were found to be of clinical significance. The method used by Shulte and Thompson (3) has been adapted for this study. METHOD OF STUDYTo study the incidence of urease-producing organisms in the oral flora unstimulated salivary samples were collected from a total of 82 patients and inoculated into "carbamide media." The media used to test for presence of ureaseproducing bacteria was similar to that prepared by Laidley and modified by Thompson and Shulte (3) (peptone 2 gms., sodium chloride 5 gms., distilled water 1000 cc., 20 cc. of a 0.2% alcoholic solution of thymol blue). The media was adjusted to pH 6.8. Ten cc. of this media was poured into each tube and sterilized by heat. After sterilization, 0.5 cc. of a Seitz filtered 10% carbamide (C.P.) solution was added to each tube and incubated for 24 hours. If not contaminated, tubes were stored in a refrigerator until used. This media is very selective for bacteria able to split carbamide.
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