18: Fusobacteria, Leptotrichia and spirochaetes

Chapter 18 Fusobacteria, Leptotrichia and spirochaetes

Fusobacteria are non-sporing, anaerobic, non-motile, non- or weakly fermentative, spindle-shaped bacilli (with fused ends: hence the name). They are normal inhabitants of the oral cavity, colon and female genital tract and are sometimes isolated from pulmonary and pelvic abscesses. Fusospirochaetal infections, which they cause in combination with spirochaetes, are noteworthy. Fusobacterium nucleatum (the type species), Fusobacterium periodontium and Fusobacterium simiae are isolated mainly from periodontal disease sites, and others such as Fusobacterium alocis and Fusobacterium sulci are sometimes found in the healthy gingival sulcus. Non-oral species include Fusobacterium gonidiaformans, Fusobacterium russii and Fusobacterium ulcerans.

Fusobacteria

Fusobacterium nucleatum

Characteristics

Gram-negative, strictly anaerobic, cigar-shaped bacilli with pointed ends (Fig. 18.1). Cells often have a central swelling. A Gram-stained smear of deep gingival debris obtained from a lesion of acute ulcerative gingivitis is a simple method of demonstrating the characteristic fusobacteria, together with spirochaetes and polymorphonuclear leukocytes (Fig. 18.2). These, together with the clinical picture, confirm a clinical diagnosis of acute ulcerative gingivitis.

Spirochaetes

Spirochaetes are a diverse group of spiral, motile organisms comprising five genera. Of these, three genera are human pathogens:

Spirochaetes are helical organisms with a central protoplasmic cylinder surrounded by a cytoplasmic membrane (Fig. 18.3). The cell wall is similar to Gram-negative bacteria but stains poorly with the Gram stain. Underneath the cell wall run three to five axial filaments that are fixed to the extremities of the organism. Contractions of these filaments distort the bacterial cell body to give it its helical shape. The organism moves either by rotation along the long axis or b/>

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Jan 4, 2015 | Posted by in General Dentistry | Comments Off on 18: Fusobacteria, Leptotrichia and spirochaetes
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