Pathogenic Anaerobic Non-spore forming Gram-negative bacteria

● Gram-negative, anaerobic bacteria

● Endospores not produced

● Enriched media required for growth

● Majority are commensals on mucosal surfaces, principally in the alimentary tract

● Opportunistic pathogens

● Synergism with other bacteria in mixed infections

● Anaerobic bacteria

● Gram-negative bacteria

● Non-spore-forming bacteria

Pathogenic anaerobic non-spore forming Gram-negative bacteria

produces foot rot in sheep in association with other pathogen

Dichelobacter nodosus

Major Genera of Vet importance: (FPPD)

Fusobacterium

Prevotella

Porphyromonas

Dichelobacter

Opportunistic infections, liver abscesses, calf diphtheria, hoof infections

Fusobacterium

Mixed anaerobic infections

Prevotella

Mixed infections, bovine necrotic vulvovaginitis

Porphyromonas

Footrot in ruminants

Dichelobacter

Anaerobic cultures are incubated using anaerobic jars containing _______ & _______

hydrogen and 10% carbon dioxide

Blood agar supplemented with _____, _____, _____, ______ is commonly used for anaerobic isolation.

5 to 10% ruminant red blood cells, yeast extract, vitamin K, and haemin

Media must first be pre-reduced in an anaerobic atmosphere for at least ______ hours before inoculation.

6

Liquid media such as cooked meat broth or thioglycollate medium supplemented with ______ and _____ are mainly used for subculturing or as backup culture material.

vitamin K and haemin

appears as thick rods that are straight or slightly curved.

They may reach up to 6 μm in length and often bulge at one or both ends.

Dichelobacter nodosus

appears as long, non-branching filamentous forms with irregular staining characteristics

Fusobacterium necrophorum

Colonies of Gram-negative anaerobes commonly produce a _____ odor because of volatile fatty acid production

foul or putrid

Virulent strains from ovine footrot lesions usually have a

dark central zone

pale granular middle zone

spreading irregular periphery with a ground glass appearance.

Dichelobacter nodosus

Colonies are grey, round and shiny. Some isolates are haemolytic.

Fusobacterium necrophorum

Become darkly pigmented after 5 days of incubation

Appear red under ultraviolet light

Prevotella and Porphyromonas

Several methods are used to detect virulent strains of Dichelobacter nodosus:

○ Elastin and gelatin gel tests detect protease activity

○ ELISA uses monoclonal antibodies against D. nodosus proteases and other antigens

○ PCR techniques detect virulence-specific genes

Many opportunistic anaerobes produce ________, an enzyme that helps them temporarily survive in oxygenated tissues until conditions become favorable for anaerobic growth

superoxide dismutase

produces a heat-labile factor that stimulates replication of Fusobacterium necrophorum

Arcanobacterium pyogenes

produces leukotoxin, which is associated with strain virulence and also supports survival of A. pyogenes.

Fusobacterium necrophorum

Synergism between ______ and _____ is important in ruminant foot lesions.

■ facilitates tissue invasion by D. nodosus.

■ produces a growth factor that stimulates F. necrophorum.

F. necrophorum

Dichelobacter nodosus

Two subspecies of Fusobacterium necrophorum are recognized.

○ is more haemolytic and more virulent.

○ is less virulent.

F. necrophorum subsp. necrophorum

F. necrophorum subsp. funduliforme

Some strains associated with oral, paraoral, and necrotizing pneumonic infections in horses have been classified as a separate species called

Fusobacterium equinum

● especially active against ruminant neutrophils but may also affect macrophages and hepatocytes.

○ It is only moderately toxic to equine neutrophils.

○ It has little or no activity against neutrophils of pigs and rabbits.

Leukotoxin

act as adhesins and promote attachment to and invasion of ruminal epithelial cells

Haemagglutinins

Endotoxin from LPS contributes to hepatic abscess formation and causes marked neutrophilia.

Lipopolysaccharide or LPS

Virulence of Dichelobacter nodosus is associated with several tissue-damaging factors.

These include:

Thermostable proteases

Elastase

Production of ______ is central to virulence.

■ These fimbriae are encoded by the _____ gene.

■ They are highly immunogenic.

■ They form the basis for classification into 10 serogroups.

Type IV fimbriae

fimA

is considered a primary pathogen in several important disease conditions of farm animals.

Fusobacterium necrophorum

Commonly presents as necrotic pharyngitis or laryngitis in calves younger than 3 months old.

○ The causative agent is ______

○ Infection occurs when the organism enters through abrasions in the pharyngeal or laryngeal mucosa.

○ These abrasions are often caused by ingestion of coarse feed.

● Clinical signs:

○ Fever

○ Depression

○ Anorexia

○ Excessive salivation

○ Respiratory distress

○ Foul smell from the mouth

Calf Diphtheria

Fusobacterium necrophorum

Treatment for Calf Diphtheria

potentiated sulphonamides or tetracyclines is usually effective.

● Most commonly seen in feedlot cattle and usually occur secondary to rumenitis.

● Feeding high-carbohydrate rations causes rapid fermentation inside the rumen.

This can lead to: Ruminal acidosis, Rumenitis, Ulcers and abscesses in the ruminal wall

● High lactate levels produced during ruminal acidosis favor the growth of Fusobacterium necrophorum because lactic acid serves as a major substrate for the organism.

● Fusobacterium necrophorum is sensitive to low pH.

Bovine liver abscess

● A sporadic disease that mainly affects young pigs. It is characterized by suppuration and necrosis of the snout caused by F. necrophorum, often together with other anaerobic bacteria.

○ The organisms usually enter through abrasions in the nasal mucosa.

● Common clinical signs include:

○ Swelling of the face

○ Sneezing

○ Foul-smelling nasal discharge

Necrotic rhinitis of pigs

In chronic cases, the infection may extend into the nasal and facial bones, leading to permanent facial deformity called _____

Bull Nose

● A necrotic condition affecting the equine hoof.

○ It is associated with poor hygiene, wet conditions, and lack of regular hoof cleaning.

○ Infection with Fusobacterium necrophorum

● The condition commonly affects the hind feet.

○ A characteristic finding is a foul-smelling discharge in the sulci near the frog.

Thrush of the Hoof

● also called black pox of the teat orifice and sphincter in dairy cows, presents as a localized area of necrosis

○ The lesion is characterized by black scab formation

○ It is caused by invasion by Fusobacterium necrophorum

● The condition may lead to stenosis of the teat sphincter

● It may also predispose affected animals to mastitis

Black spot of bovine teats