Anaerobes Flashcards
Characteristics of Anaerobic Bacteria
- most infections are of endogenous origin
- Require anaerobic environment/devitalized tissue
- Obligate anaerobes do not tolerate oxygen
Gram Positive Anaerobes
spore forming (ex Clostridium)
Gram Negative Anaerobes
not spore forming (ex Fusobacterium necrophorum)
Sign of Anaerobic Infection
infection not responding to treatment with aminoglycosides
What is a predisposing factor to infection with Clostridium?
necrosis
Major types of Disease caused by Clostridium
- neurotoxic- toxic to nerves
- Histotoxic- affect tissues
- Enterotoxic- damage GI tract
Neurotoxic Clostridium
C. botulinum, C. tetani, C. perfringens
Histotoxic Clostridium
C. chauvoei, S. septicum, C. novyi,
Enterotoxic Clostridium
C. perfringens, C. difficile
Clostridium tetani
causes tetanus. Produces potent neurotoxin. More common in horses.
Clostridium tetani pathogenesis
- wound infection
- toxin produced in wound
- toxin enters motor nerves
- retrograde transport
- prevents release of neurotransmitters glycine and GABA
- spastic paralysis
What neurotoxin is produced by Clostridium tetani?
Tetanospasmin
Ascending tetanus
occurs in less susceptible animals (dogs and cats)
Descending Tetanus
occurs in more susceptible species (horses and humans)
Clostridium tetani Diagnosis
clinical signs and history of recent wound. Culture often unrewarding and serology not useful
Clostridium tetani Treatment
antitoxin, antimicrobial, supportive care
Clostridium tetani Control
immunization, wound management, aseptic techniques
Clostridium botulinum
causes botulism.
Botulism
caused by food intoxication due to consumption of food contaminated with botulinum neurotoxin. Inhibits neurotransmitter release (acetylcholine) and causes flaccid paralysis
Botulism clinical signs
symmetrical flaccid paralysis of muscles. Because of the lack of pathological changes and sometimes apparently vague symptomology such as downer cow, it can be missed as a diagnosis
Botulism Diagnosis
not always practical.
Botulism Treatment
antitoxin neutralizes unbound toxin only and is useful only if animal is still actively absorbing toxin, once toxin enters blood stream it is quickly bound to receptors
Black Leg
caused by Clostridium chauvoei. Endospores are ingested and migrate through lymphatics or blood stream to muscle. Metabolic products of fermentation often have distinctive smells. Activation of endogenous spores in muscle
Clostridium septicum
causes malignant edema (gas gangrene). Also causes Braxy in sheep and necrotic dermatitis in chicken
Clostridium septicum Diagnosis
- direct gram staining
2. direct fluorescent antibody test
Clostridium perfringens Type D
causes enterotoxin in sheep and goat (overeating disease). Focal symmetrical encephalomalacia. Rapid postmortem autolysis of the kidneys resulting in a pulpy kidney
Clostridium difficile
Causes enterocolitis. Dysbiosis/dysbacteriosis
Clostridium difficile Risk Factors
recent antibiotic use, old age, hospitalization
Dysbiosis
general microbial imbalance of the body
C. difficile Diarrhea Treatment
- antimicrobials in severe cases
- Probiotics- lactobacillus, Saccharomyces replaces flora
- Avoid anti-diarrheals- result in accumulation of toxin
- Fecal transplantation
Clostridium spiroforme
causes explosive diarrhea in rabbits 4-8 weeks old. Antibiotics, lincomycin, clindamycin, and erythromycin are contraindicated in rabbits.
Why are antibiotics contraindicated in rabbits?
they induce Clostridium-related enterotoxemia due to their selective effect on normal gram-positive bacteria
Clostridium Piliforme
gram negative Clostridium that causes Tyzzers disease in lab animals. Cannot be cultured
Tyzzers Disease
disease of lab animals caused by Clostridium piriforme. Associated with focal liver necrosis.
Fusobacterium necrophorum
involved in liver abscess and foot rot in cattle and sheep
General guidelines for treatment
aminoglycosides, sulfonamides are not effective. Antimicrobials. Depends on condition
Anaerobic Bacteria Transmission
spread by direct extension from mucosal surfaces
General Guidelines for Prevention
vaccination for foot rot. Hygiene and management of wounds
Characteristics of necrosis
- provides an initial opportunity for Clostridium to grow
- the host response to many Clostridial infections
- facilitates the rapid spread of infection through the body
Anaerobic species
Clostridium tetani Clostridium botulinum Clostridium perfringes Clostridium difficile C. septicum C. chauveoi C. novyi
What toxin is in all Clostridium perfringens?
Alpha Toxin
Most lethal endotoxin produced by Clostridium perfringens
Epsilon toxin
