Lec. Fusobacteria

University of Babylon
Collage of Dentistry
Lec. Fusobacteria
Fusobacteria are non-sporing, anaerobic, non-motile, non- or weakly fermentative, spindle-shaped bacilli). 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. Fusobacterium nucleatum. 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.
Fusobacterium nucleatum
Habitat and transmission
Several subspecies of F. nucleatum have been identified in different habitats. Infections are almost endogenous. These include F. nucleatum found in the healthy gingival crevice and recovered mainly from periodontal pockets.
Characteristics
Gram-negative, strictly anaerobic, cigar-shaped bacilli with pointed ends. 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. These, together with the clinical picture, confirm a clinical diagnosis of acute ulcerative gingivitis.

Culture and identification
Grows on blood agar as dull, granular colonies with an irregular, rhizoid edge. Biochemical reactions and the acidic end products of carbohydrate metabolism help identification. Fusobacterium also associated with halitosis.
Pathogenicity
The endotoxin of the organism appears to be involved in the pathogenesis of periodontal disease. It possesses remarkable adherence properties and the fusobacterium adhesin A (FadA), which confers this property has recently been isolated. F. nucleatum is usually isolated from polymicrobial infections; it is rarely the sole pathogen. Thus, in combination with oral spirochaetes (Treponema vincentii and others), it causes the classic fusospirochaetal infections. These are:
¥ acute (necrotizing) ulcerative gingivitis
¥ Vincent’s angina, an ulcerative tonsillitis causing tissue necrosis, often due to extension of acute ulcerative gingivitis.

¥ cancrum oris or noma: a sequela of acute ulcerative gingivitis with resultant gross tissue loss of the facial region. As fusobacteria coaggregate with most other oral bacteria, they are believed to be important bridging organisms between early and late colonizers during plaque formation

¥ Antibiotic sensitivity and prevention
Fusobacteria are uniformly sensitive to penicillin and metronidazole. Regular oral hygiene and antiseptic mouthwashes are the key to prevention of oral fusobacterial infections in susceptible individuals.

¥ Leptotrichia

Leptotrichia spp. are oral commensals previously thought to belong to the genus Fusobacterium. They are Gram-negative, strictly anaerobic, slender, filamentous bacilli, usually with one pointed end. Stright or curved rod shaped. The Leptotrichia cell measures 0.8-1.5 ?m × 5–20 ?m. Cells normally organize as pairs or in a chain. The cells do not produce spores and are nonmotile.


Leptotrichia buccalis, present in low proporation in dental plaque.
¥ Genus Leptotrichia
Gram-negative filaments with at least one pointed end:

• Main species: Leptotrichia buccalis.

• Cultural characteristics: strict anaerobes, with colonies resembling Fusobacteria. After culturing in anaerobic blood agar for 1–2days, Leptotrichia can form 1–2 mm, raised, and transparent colonies with smooth and filamentous edges. Sometimes polymorphous colonies are also formed.
Cultures require 5–10% CO2. The ideal temperature for culture growth is between 35 °C and 37 °C, while Leptotrichia cells stop growing when temperatures drop below 25°C. The ideal pH for culturing these cells is between pH 7.0 and 7.4. Growth is not inhibited by 20% bile.
Leptotrichia is biochemically active. It can ferment amygdalin, cellobiose, fructose, glucose, maltose, mannose, melezitose, salicin, sucrose, and trehalose to produce acid.
• Main intraoral sites and infections: dental plaque. No known disease association.

BOOKS:
Essential microbiology for dentistry 2012. Elsevier Ltd. FOURTH EDITION Lakshman Samaranayake. Elsevier Ltd.
Atlas of oral microbiology.from healthy microflora to disease. Xuedung Zhou,Yuqing Li. 2015. Sichuan University, Chengdu, China.



Prepared by A. Prof. Dr. Zainab Khudhur Ahmad