Chapter 37: Pathogenic anaerobic non-spore-forming Gram-negative Bacteria Flashcards
Often in association with
facultative anaerobes
Type of bacteria
Gram-negative
Emvironment
Anaerobic bacteria
Endospores
Not produced
Requirement
Fastidious: enriched media
Commensals in
Mucosal surfaces, principally in the alimentary tract
Synergism with other bacteria in mixed infections
True
Produces foot rot in sheep in association with other pathogens
Dichelobacter nodosus
50% of this organism isolated from/ constitutes:
-Fusobacterium spp
-Prevotella genus
-Dichelobacter genus
-Porphyromonas genus
Usual habitat
-Mucous membranes of animals and humans
-Particularly in digestive and urogenital tracts
-Excreted in feces
-Survive for short periods
Differentiated based on
-Bacterial morphology
-Colonial appearance
-Antibiotic susceptibility testing
-Fatty acid production
Bacterial morphology:
Dichelobacter nodosus
-Thick, straight or slightly curved rods
-6 um long,
-bulge at one or both ends
Bacterial morphology:
Fusobacterium necrophorum
-irregularly staining
-long, nom-branching filamentous forms (Fig. 37.1)
Colonies usually have
-Foetid or putrid ordor
Colonies have ordor due to
Volatile fatty acid production
Virulent strains from ovine foot rot lesions:
-have dark central zone
-pale granular middle zone
-spreading irregular periphery
-with a ground glass appearance
Fusobacterium necrophorum colonial appearance
-grey, round, shiny
-some isolates are hemolytic
Prevotella and Porphyromonas colonial appearance:
-Become darkly pigmented after incubation (5 days)
-May appear red under UV light
For accurate identification of species:
-Antibiotic susceptibility
-Biochemical test
-Gas liquid chromatography
Methods for detecting virulent strains of Dichelobacter nodosus:
-Elastin and gelatin gel test
- ELISA
-Polymerase chains reaction
-Molecular tests
Detection of proteases activity
-Elastin and gelatin gel test
Using monoclonal antibodies
ELISA
Detection of virulence-specific genes
PCR
-PCR techniques
-For grouping strains of Dichelobacter nodosus
Molecular tests
Replicate only at
Low or negative reduction potentials (Eh)
Opportunistic pathogens which produces
superoxide dismutase
Superoxide dismutase functions
-allows them to survive in oxygenated tissues until Eh reaches levels favoring their growth
_____ and _____ followed by _____ of the bacteria can lower Eh levels to a range suitable for the proliferation of the bacteria
-Tissue trauma
-Necrosis
-multiplication of the bacteria
Produces heat-labile factor which stimulates F. necrophorum replication
Arcanobacterium pyogenes
Produces leukotoxin which correlates with the strain virulence and aids survival of A. pyogenes
-F. necrophorum
Is important in the pathogenesis of ruminant pedal lesions
Synergism between F. necrophorum and Dichelobacter nodosus
Facilitates tissue invasion by D. nodosus and is itself stimulated by a _____ elaborated by D. nodosus
-F. necrophorum
-growth factor
2 or more bacteria interacting synergistically. Produce lesions which the individual organism cannot produce. Example of this type of synergism
-Production of a heat-labile factor by Arcanobacterium pyogenes, which stimulates F. necrophorum replication
-In turn, F. necrophorum produces leukotoxin which correlates with the strain virulence and aids survival of A. pyogenes
-Synergism between F. necrophorum and Dichelobacter nodosus is important in the pathogenesis of ruminant pedal lesions
-In this instance, F. necrophorum facilitates tissue invasion by D. nodosus and is itself stimulated by a growth factor elaborated by D. nodosus
2 subsp of *F. necrophorum are recognized:
-F. necrophorum subsp. necrophorum
-F. necrophorum subsp funduliforme
-has greater haemolytic activity
-more virulent than subsp. funduliforme
-F. necrophorum subsp. necrophorum
-produces oral,
-paraoral and
-necrotizing pneumonic infections in horses
-classified as new species
-F. necrophorum?
-F. equinum?
F. necrophorum virulence factor:
-Leukotoxin
-Haemagglutinins
-Haemolysins
-Dermotoxin
-Other extracellular enzymes
-Lipopolysaccharide (LPS)
-important virulence determinants
-active against ruminant neutrophils
-but may act also against macrophages and hepatocytes
-moderately toxic for: equine neutrophils
-little or no activity against: neutrophils of pigs and rabbits
Leukotoxin
-important virulence determinants
-function as adhesins and promote adherence to,
-and invasion of ruminal epithelial cells
-Haemagglutinins
-contribute to the development of ruminal lesions
-important virulence determinants
-endotoxin from this is important in the genesis of hepatic abscesses and induces an intense neutrophilia
Lipopolysaccharide (LPS)
Characteristic of D. nodosus
-Ability to damage tissues
-production of thermostable proteases and elastase
-presence of argarolytic activity on agar- based media containing powdered hoof
-production of type IV fimbriae, encoded by the fimA gene
-is central to virulence
-highly immunogenic structures
-form basis of classification of D. nodosus strains into 20 serogroups
Characteristic of D. nodosus:
-Production of type IV fimbriae, encoded by the fimA gene
Calf diphtheria
-F. necrophorum
Bovine liver abscess
-F. necrophorum together with Arcanobacterium pyogenes (feedlot animals)
Necrotic rhinitis of pigs (bull nose)
-F. necrophorum
Thrush of the hoof
-* F. necrophorum*
-secondary to hoof damage (hind feet-frog)
Black spot of bovine teats
-F. necrophorum
Specific syndrome of bovine necrotic vulvovaginitis
-Association with Porphyromonas levi
-Israeli dairy herds
-Straight or curved rods
-characteridtic swellings at one or both ends
-Dichelobacter nodosus
-slender, non-branching filaments
-stain irregularly
-Fusobacterium necrophorum
Tissue damage facilitates invasion by D. nodosus
Fusobacterium necrophorum —> Dichelobacter nodosus
Growth factor
-D. nodosus—-> F. necrophorum
-Arcanobacterium pyogenes—-> F. necrophorum
Leukotoxin facilitates survival of A. pyogenes
F. necrophorum —> A. pyogenes
Gram-negative, non-spore-forming anaerobes which have been implicated in infections in domestic animals
14 spp.
-Bf
-OBs
-Bh
-Dn
-Fe
-Fn
-Fn
-Fr
-OFs
-Pa
-Pl
-Ph
-Pm
-S
(F. necrophorum)
Predisposing factors:
Rough feed producing mucosal damage
-Disease condition
-Species
-Calf diphtheria
-Cattle
(F. necrophorum)
Predisposing factors: Dystocia
-Disease condition
-Species
-post-partum metritis
-cattle
(F. necrophorum)
Predisposing factors: Sudden dietary change leading to acidosis and rumenitis
-Disease condition
-Species
-hepatic abscessation
-cattle
(F. necrophorum)
Predisposing factors: Trauma to region adjacent to teat sphincter
-Disease condition
-Species
-Black spot of teat
-cattle
(F. necrophorum)
Predisposing factors: Poor hygiene and wet housing conditions
-Disease condition
-Species
-thrush (hoof)
-Horses
(F. necrophorum)
Predisposing factors: Poor hygiene
-Disease condition
-Species
-Necrobacillosis of lower limbs
-horses
(F. necrophorum)
Predisposing factors: trauma to nasal mucosa
-Disease condition
-Species
-bull nose
-pigs
(Mixed infections)
Bacteria implicated: F. necrophorum, Dichelobacter nodosus (benign strains)
-disease condition
-species
-Interdigital dermatitis
-sheep
(Mixed infections)
Bacteria implicated: Arcanobacterium pyogenes (facultative anaerobes), F. necrophorum and other bacteria
-disease condition
-species
-heel abscess and lamellar suppuration
-sheep
(Mixed infections)
Bacteria implicated: D. nodosus, F. necrophorum, A. pyogenes, unidentified spirochaetes
-disease condition
-species
-footrot
-sheep
(Mixed infections)
Bacteria implicated: F. necrophorum, Porphyromonas levii
-disease condition
-species
-Interdigital necrobacillosis (foul-in-the-foot)
-cattle
(Mixed infections)
Bacteria implicated: D. nodosus, F. necrophorum, Prevotella species, spirochaetes
-disease condition
-species
-interdigital dermatitis
-cattle
(Mixed infections)
Bacteria implicated: Treponema species
-disease condition
-species
-Digital dermatitis
-cattle
(Mixed infections)
Bacteria implicated: Mixed anaerobes
-disease condition
-species
-foot abscess in young pigs and bush foot (lamellar suppuration) in older animals
-pigs
