5.11 Gram negative anaerobes: Fusobacterium necrophorum, Dichelobacter nodosus, and Mycoplasma spp. Flashcards
(40 cards)
Fusobacterium necrophorum characteristics; shape, gram stain, aerobe/ anaerobe, habitat, type of pathogen and infections
- Filamentous Gram-negative rods
- Obligate anaerobes
- Part of normal flora on mucous membranes, GI tract
- Opportunistic, mixed infections
- Disease often follows trauma to anatomical barriers
- May co-occur with facultative anaerobes that help reduce the redox environment for their growth or have synergistic effects
Fusobacterium necrophorum primary disease in cattle and symptoms? what other diseases and symptoms does it cause?
- In cattle, it plays a primary role:
- Calf diphtheria
– Necrotic pharyngitis/laryngitis
– If untreated may progress to fatal necrotizing pneumonia
Digital dermatitis (foot-rot in cattle):
-Synergism with Treponema spp.
Hepatic abscesses in cattle:
* Hepatic abscesses (called necrobacillosis)
* Secondary to ruminitis, common in feedlot animals, often no clinical signs
* High grain diet=> acidosis=> rumenitis=> invades to liver=> causes abscesses
* May rupture=> LPS=> endotoxemia=> sudden death
Nature of and pathogenesis of liver disease caused by Fusobacterium necrophorum in cattle
- Hepatic abscesses (called necrobacillosis)
- Secondary to ruminitis, common in feedlot animals, often no clinical signs
- High grain diet=> acidosis=> rumenitis=> invades to liver=> causes abscesses
- May rupture=> LPS=> endotoxemia=> sudden death
Primary causal agent of footrot in sheep? what other bacteria is involved?
Dichelobacter nodosus
- F. necrophorum initiates the lesion but does not
progress without a virulent strain of D. nodosus
Dichelobacter nodosus physical characteristics
Large rods with terminal swellings and long, polar fimbriae
Dichelobacter nodosus virulence factors
Virulence factors: fimbriae for adherence, proteases, elastases damage tissue
Dichelobacter nodosus possible disease association in cattle
possibly associated with digital dermatitis
what disease does Dichelobacter nodosus cause in sheep?
ovine footrot
what is the pathogenesis of ovine footrot? Essential pathogen
skin damage
> interdigital dermatitis
> virulent dichelobacter nodosus
> footrot w/ F. necrophorum and other bacteria
D. nodosus: essential pathogen for underrunning footrot to develop
Dichelobacter nodosus; aerobe or anaerobe? virulent or benign?
- Anaerobic
- Virulent or benign
Dichelobacter nodosus can only grow on what culture medium? how is it prepared?
hoof agar
-feet collected at abbatoir, boiled, separated…hoof powder made
physical characteristics of mycoplasma; size, genome, cell structure, habitat
- Smallest free-living bacteria; 0.3 μm diameter, small genome
- Lack cell wall (Don’t stain Gram)
- Obligate parasites (extracellular)
- Poor environmental survival
transmission of mycoplasma
- Infection mainly by close contact of animals (aerosols on short distances)
anatomic locations where mycoplasma causes disease
- Diseases mostly localized (respiratory tract ++++, genital tract +, conjunctiva +, udder+, sometimes septicemia)
what species does mycoplasma infect? is it often diagnosed and why?
- Affect many animal species
- Very fastidious => often underdiagnosed
how many species of mycoplasma are there? are they pathogens or commensals?
> 100 species
Pathogens and commensals
important way that mycoplasma leads to disease
causes predisposition to “secondary bacterial infections”
important mycoplasma disease that infects poultry and other birds
M. gallisepticum
clinical disease caused by M. gallisepticum in chickens and turkeys
Chicken: Chronic Respiratory
Turkey: Infectious Sinusitis
Mycoplasma gallisepticum; how is it transmitted, how does infection progress through the body, who becomes a carrier, is it easy to differentiate from other mycoplasma?
- Most pathogenic avian mycoplasma
- Vertical (egg-transmitted) & horizontal transmission
- Infects conjunctive and nasal passages first, may progress to bronchi & lungs
- Infected animals are carriers for life
- Must differentiate from commensal mycoplasmas
Most pathogenic avian mycoplasma
Mycoplasma gallisepticum
How does Mycoplasma gallisepticum cause disease?
- vertical or horizontal transmission
- localize in the epithelium of respiratory tract
- bacteremia
- irritation and damage to epithelial lining of respiratory system (tracheitis, loss of cilia)
- pneumonia/ ovary infection
- clinical signs/lesions
>loss of production
>morbidity
>mortality
Mycoplasma hyopneumoniae causes what disease in pigs? symptoms and character of the disease?
Enzootic pneumonia
- Chronic anteroventral bronchopneumonia of pigs,
common - Adheres ciliated epithelium bronchi, bronchioles
- Infection ciliated epithelium persists months
- Predisposes to secondary bacterial infections; impairs bacterial clearance
Mycoplasma hyopneumoniae; how is it spread?
- Mostly spread by direct contact, aerosols
- Acquired from sow, spread in weaner-grower pigs
