Changes

*Characteristics:

**Normal inhabitant of mammalian gut; cannot invade normal tissue

 

**Pleimorphic - long and filamentous or short cocci

| Also known as:

**Haemolytic on blood agar

**Grey, round, shiny colonies

**Three biotypes: biotype A has greatest haemolytic activity and virulence

*Pathogenesis and pathogenicity:

 

**Primary pathogen in various diseases of farm animals

 

**Mixed bacterial infections

''F.necrophorum'' is a [[Pathogenic anaerobic non-spore-forming Gram-negative species - Overview|pathogenic, anaerobic, non-spore-forming Gram-negative bacteria]]. It is a normal inhabitant of the mammalian gut and cannot invade normal tissue.

**Can be secondary to [[Infectious Bovine Rhinotracheitis|IBR]]

 

**Extracellular haemolysin contributes to infection

**Heat-stable leucocidin - correlated with biotype and virulence

''F.necrophorum'' is pleimorphic and is either long and filamentous or a short cocci. It is fermentative and haemolytic on blood agar. It produces grey, round and shiny colonies. There are three biotypes, biotype A has the greatest haemolytic activity and virulence.

**Cytoplasmic toxin - haemolytic  

 

**LPS endotoxin causes host damage

==Pathogenesis and pathogenicity==

**Antibodiy levels rise with age, suggesting that these are not protective

''F.necrophorum'' is a primary pathogen in various diseases of farm animals. It forms mixed bacterial infections and can be secondary to [[Infectious Bovine Rhinotracheitis|IBR]].

Extracellular haemolysin contributes to infection and heat-stable leucocidin is correlated with biotype and virulence. Cytoplasmic toxin is haemolytic and LPS endotoxin causes host damage.

Antibody levels to ''F.necrophorum'' rise with age, suggesting that these are not protective.

 

**Associated with bucket feeding where buckets are contaminated with faeces

''F.necrophorum'' is associated with bucket feeding, where buckets are contaminated with faeces. Bacteria enter through abrasions in the mucosa of the pharynx and larynx and cause fever, depression, anorexia, salivation, respiratory distress and halitosis. Aspiration of necrotic material into lungs may cause fatal [[Lungs Inflammatory - Pathology#Infectious causes of neumonia|bronchopneumonia]].

**Bacteria enter through abrasions in the mucosa of the pharynx and larynx

 

**Fever, depression, anorexia, salivation, respiratory distress and halitosis

''F.necrophorum'' causes a number of necrotic wound infections often in association with facultative anaerobes.

**Aspiration of necrotic material into lungs may cause fatal [[Lungs Inflammatory - Pathology#Infectious causes of neumonia|bronchopneumonia]]

 

'''Cows'''

[[Calf Diphtheria|Calf diphtheria]] or necrotic laryngitis [[Respiratory Bacterial Infections - Pathology#In Cattle|in cattle]] and necrobacillosis of the mouth and pharynx of young calves. Also, [[Bovine liver abscesses]] and localised necrosis and scab formation of the teat orifice and sphincter of dairy cows.

**Ulceration of rumenal mucosa and colonisation by ''F. necrophorum'' and [[Arcanobacter pyogenes|''Arcanobacter pyogenes'']]

 

'''Pigs'''

**Focal necrosis and abscess formation in liver

[[Necrotic rhinitis]] in pigs.

 

Interdigital dermatitis ([[Bacterial skin infections - Pathology#Bacterial pododermatitis|pododermatitis]]) in sheep in association with ''D. nodosus'' and [[Arcanobacter pyogenes|''Arcanobacter pyogenes'']], predisposing to footrot. It also causes [[Respiratory Bacterial Infections - Pathology#Laryngeal chondritis|laryngeal chondritis]] in sheep and mixed infections in heel abscesses.

 

''F.necrophorum'' is also involved in; [[Thrush - Hoof|Hoof thrush]]; Mixed infections in [[Pleural Cavity & Membranes Inflammatory - Pathology#Pyothorax (Thoracic empyema)|pyothorax]]; Mixed infections in aspiration pneumonia and in bovine traumatic reticuloperitonitis and pericarditis; [[Bacterial skin infections - Pathology#Subcutaneous abscesses|subcutaneous abscesses]] due to cat bites; [[Nasal Cavity Inflammatory - Pathology#Chronic rhinitis|chronic fibronecrotic rhinitis]]; [[Bones Inflammatory - Pathology#Osteitis|Osteitis]]; [[Contagious Footrot]]; [[Necrobacillosis]] and [[Laryngeal Chondritis]]

 

**''F. necrophorum'' and other organisms enter through abrasions in snout mucosa

**Occasional pharyngitis/laryngitis [[Respiratory Bacterial Infections - Pathology#In Pigs|in pigs]]

*Thrush of the hoof:

**Necrosis of horse hoof associated with poor hygiene, wet conditions

**''F. necrophorum'' secondary to hoof damage causes localised inflammatory response

**Localised necrosis and scab formation of teat orifice and sphincter of dairy cows due to ''F. necrophorum''

*Necrotic wound infections often in association with facultative anaerobes

*Interdigital dermatitis ([[Bacterial skin infections - Pathology#Bacterial pododermatitis|pododermatitis]]) in sheep in association with ''D. nodosus'' and [[Arcanobacter pyogenes|''Arcanobacter pyogenes'']], predisposing to footrot

*Causes [[Respiratory Bacterial Infections - Pathology#Laryngeal chondritis|laryngeal chondritis]] in sheep

*Mixed infections in heel abscesses in sheep

*Mixed infections in [[Pleural Cavity & Membranes Inflammatory - Pathology#Pyothorax (Thoracic empyema)|pyothorax]]

*Mixed infections in aspiration pneumonia and in bovine traumatic reticuloperitonitis and pericarditis

*Involved in [[Bacterial skin infections - Pathology#Subcutaneous abscesses|subcutaneous abscesses]] due to cat bites

*May be involved in [[Nasal Cavity Inflammatory - Pathology#Chronic rhinitis|chronic fibronecrotic rhinitis]]

*[[Bones Inflammatory - Pathology#Osteitis|Osteitis]]

*[[Contagious Footrot]]

*[[Necrobacillosis]]

*[[Laryngeal Chondritis]]

[[Category:Pathogenic anaerobic non-spore-forming Gram-negative ]]

[[Category:Pathogenic anaerobic non-spore-forming Gram-negative ]]

[[Category:To_Do_-_Bacteria]]

[[Category:To_Do_-_Bacteria]]