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Abstract
Leptotrichia buccalis varies with respect to cellular and colonial morphology, fermentation of sugars and presence of glucosidases. It can be confused with Fusobacterium spp. and gram-positive bacilli related to Lactobacillus. The aim of the present study was to examine the heterogeneity of 60 Leptotrichia isolates, of which 58 had been assigned as L. buccalis and two as ' Leptotrichia pseudobuccalis ' by using enzymatic/biochemical and cellular fatty acid analyses. The rapid ID 32 A kit (API, bioMérieux, Marcy-l'Etoile, France) revealed considerable strain heterogeneity. Most frequently detected were strains producing f -glucosidase, alkaline phosphatase and g -glucosidase. Three other prominent strain clusters generated g -galactosidase-6-phosphate, g -galactosidase and f -galactosidase, respectively. g - N acetyl-glucosaminidase was also produced by many strains. Mannose and raffinose fermentation was common and all strains were indole negative. Four strains reduced nitrate, and one strain produced urease. The diagnosis L. buccalis was achieved for 36 of the 60 (60%) Leptotrichia isolates. The MIDI (Microbial ID, Inc., Newark, DE, USA) system demonstrated that the most abundant cellular fatty acids were C 16:0 FA (32-59%) and C 18:1 - cis 11/t9/t6 FA or an unidentified compound with an equivalent chain length (ECL) of 17.8 (21-42%). C 12:0 FA (3-16%), C 15:0 DMA or 3-OH C 14:0 FA (4-14%), C 14:0 FA (3-20%), and C 16:1 - cis 9 FA (1-5%) were also detected. Forty-two of the strains (70%) contained C 18:1 - cis 9 FA (1-9%) and 37 (62%) C 18:2 - cis 9,12 FA (1-6%). The MIDI system came up with the diagnosis L. buccalis in 57 of the 60 isolates (95%). There was complete agreement in diagnosis between the two systems in 34 of the 60 isolates (57%). The heterogeneity in enzymatic/biochemical reactions and cellular fatty acid composition may indicate that the genus Leptotrichia contains hitherto unrecognized species.
