Lecture 14 Flashcards
Describe the appearance & metabolism of non-spore forming anaerobes
Gram negative
Obligate anaerobes
What pathological conditions do we normally find non-spore forming anaerobes?
necrotic & suppurative
What is the appearance of Fusobacterium necrophorum? (2)
Gram negative
Long, slender rods
What is the appearance of Dichelobacter nodosus? (3)
Gram negative
Straight or slightly curved rods
Characteristic swellings at both ends
What is the appearance of Prevotella melaninogenica? (3)
Gram negative
Coccobacilli
Rounded ends
Where are non-sporing forming anaerobes found? & when do they become a prob?
Normal microbiota
When they enter normally sterile sites & cause tissues to be ischemic
What part of the microbiota is Fusobacterium found?
GIT
What part of the microbiota is DIchelobacter nodosus found?
ruminant foot
What part of the microbiota are prevotella spp found?
mouth of a variety of spp
What is the virulence factor of Fusobacterium necrophorum?
Leukotoxin - lysis of bovine leukocytes & toxic towards hepatocytes
What are the virulence factors for Dichelobacter nodosus? (2)
Type IV fimbriae - motility, adherence & facilitates secretion of serine proteases
Serine proteases - degradation of hoof PROs
How do we base tx for non-spore forming anaerobes?
Site of infection, not ID
Why is Fusobacterium necrophorum problematic?
It allows invasion of other bacteria
Releases a leukotoxin causing tissue damage enabling other microbes to invade, colonize & replicate
What microbe is assoc with Fusobacterium necrophorum infection in cattle?
Trueperella pyogenes
How does Fusobacterium necrophorum infection in cattle present? (3)
Calf diphtheria - necrotic foci on larynx, trachea & buccal cavity
Symptoms: fever, depression, excessive salivation
Liver abscesses in feedlot cattle
Lesions on hoof following trimming (foul of the foot)
What is the pathogenesis of calf diphtheria caused by Fusobacterium necrophorum?
Abrasions of pharynx due to rough feed provide portal of entry
Progresses to fatal pneumonia if untreated
What is the pathogenesis of calf liver abscesses caused by Fusobacterium necrophorum?
Leukotoxins kill leukocytes in the liver resulting in abscesses
Septic embolism following rumenitis
What is the appearance of Fusobacterium necrophorum? (3)
Thin rods
Gram negative
Irregular staining
What disease does Dichelobacter nodosus cause in sheep?
Foot rot (ovine digital dermatitis)
What microbe is often assoc with Dichelobacter nodosus causing ovine foot rot?
Fusobacterium necrophorum
How do sheep present with foot rot due to Dichelobacter nodosus? What is infection assoc with?
Lameness
Underrunning of the hoof
Separation of hoof from skin horn junction
Foul smelling exudate
Infection associated with warm & wet conditions
How does Dichelobacter nodosus do in the envr?
Doesn’t readily survive
Primary reservoir is infected sheep - transmitted via transiently contained enviers (tricks, paddocks etc.)
How should you handle samples of non-spore forming anaerobes?
Avoid contamination (since they are apart of the microbiota)
Aerobic swabs are a must
What specimens should you take to test for non-spore forming anaerobes?
Purulent material from abscesses
Discharges
Tissue specimens - take larger tissue to maintain microenvrs
How are non-spore forming anaerobes dx in lab? (3)
Dilute carbol fuchsin stain of smear (since they are gram neg)
Anaerobic culture - blood agar with special supplements & requires an anaerobic chamber
PCR to identify
Do non-spore forming anaerobes pose a zoonotic risk?
Not really since they are apart of the microbiota
Although, Fusobacterium, Porphyromonas & Prevotella have all been isolated from dog & cat bites
How do you tx foot rot? What do we need to be aware of?
Tx depends on site of infection
Combo of systemic a/bs & topical antiseptics
Beware of copper toxicity in sheep when using Cu based products
How do you tx Fusobacterium necrophorum?
penicillin
How do you control non-spore forming anaerobes?
Dietary management
Paddock & pasture management to keep feet dry & clean
Describe the appearance of Capnocytophaga canimorsus?
Gram negative rods
Where is Capnocytophaga canimorsus found?
Mouths of 74% of healthy dogs
Does Capnocytophaga canimorsus pose a zoonotic risk?
Yes, infections via dog bites & sometimes cat bites or scratches
What human pops does Capnocytophaga canimorsus pose a threat to? (4)
Particularly, splenectomised people
Infections more common in older adults
Immunocompromised indivs
Alcoholism + hepatic cirrhosis
