Lecture 10 9/27/23 Flashcards
What are the general characteristics of anaerobic bacteria?
-need anaerobic environment
-do not tolerate oxygen
-must transport anaerobically
-can be gram pos. or gram neg.
-polymicrobial infections are common
What signs are consistent with anaerobic infection?
-foul smelling
-gas buildup
-necrotic tissue
-abscesses
-pyogranulomatous lesions w/ sulfur granules
-infections near mucous membranes
-not responsive to aminoglycosides
-disease despite negative aerobic culture
What are the characteristics of Clostridium sp.?
-gram pos
-spore forming
-rods
-produce exotoxins
What are the three major types of disease caused by Clostridium sp.?
-neurotoxic
-histotoxic
-enterotoxic
Which Clostridium sp. causes all three types of disease?
C. perfringens
What are the characteristics of C. tetani?
-causes tetanus
-grows in contaminated wounds
-produces potent neurotoxin
-can affect all species
How does the C. tetani neurotoxin act on the body?
prevents release of glycine and GABA neurotransmitters, leading to spastic paralysis
What is ascending tetanus?
toxin begins in limb and spreads to other parts of body; limbs affected first
What is descending tetanus?
toxin in blood stream affects head and neck first; spread to limbs secondary
How is C. tetani diagnosed?
clinical signs and wound history
How can tetanus be treated?
-antitoxin
-anti-tetanus serum
-antimicrobials
-surgical debridement
-supportive care
How can C. tetani be controlled?
-toxoid immunization
-post exposure prophylaxis
-proper wound management and aseptic techniques
What are the characteristics of C. botulinum?
-causes botulism via botulinum neurotoxin
-disease caused by food intoxication
-most powerful exotoxin
-inhibits neurotransmitter release
-flaccid paralysis
-select agent
How is C. botulinum diagnosed?
-demonstration of toxin in serum
-bioassay/neutralization tests
-ELISA
How is C. botulinum treated?
-antitoxin
-therapeutic drugs
-supportive care
How is C. botulinum controlled?
-toxoid vx. for high risk animals, but no routine vx.
-avoid feeding soiled food
Which histotoxic Clostridia are of importance?
-C. chauvoei
-C. septicum
-C. novyi
-C. perfringens
What disease is caused by C. chauvoei?
black leg
What are the characteristics of black leg?
-ingested endospores lead to trauma and tissue necrosis
-distinctive smells of fermentation end products
-characteristic edematous and emphysematous swellings
What diseases are caused by C. septicum?
-malignant edema
-braxy
-necrotic dermatitis
What are the two types of malignant edema infections?
-exogenous through wounds
-endogenous through dormant spores in meat/tissue
What infections are caused by C. novae?
-exogenous gas gangrene
-endogenous black disease
-endogenous liver damage and bacillary hemoglobinuria
How can the histotoxic Clostridium sp. be diagnosed?
-gram stain
-fluorescent antibody staining test
What antibiotic is used against histotoxic Clostridium sp.?
penicillin
How can histotoxic Clostridium sp. be controlled?
routine vx
What are the characteristics of C. perfringens?
-classified based on combinations of four toxins (alpha, beta, iota, epsilon)
-all species have alpha toxin
-cause enteric disease
Which C. perfringens type is most important?
Type D
What are the characteristics of C. perfringens type D?
-causes enterotoxemia
-fluid-distended intestine with petechial hemorrhage
-focal symmetrical encephalomalacia
-pulpy kidney
How is C. perfringens diagnosed?
-gram stain
-anaerobic culture
-toxin detection
How is C. perfringens treated?
hyperimmune serum
How is C. perfringens controlled?
-immunization
-avoiding sudden changes in diet and stress
What are the characteristics of C. difficile?
-causes enterocolitis
-proliferate rapidly once antimicrobial treatment kills flora and is removed
-risk factors include recent antibiotic use, old age, and hospitalization
How is C. difficile diagnosed?
-culture
-toxin antigen detection
How is C. difficile treated?
-supportive care
-stopping antimicrobials in most cases
-using antimicrobials in severe cases
-probiotics
-fecal transplantation
What are the characteristics of C. spiroforme?
-commensal that produces Iota toxin
-causes enterotoxemia and explosive diarrheal disease in rabbits
-some antibiotics are contraindicated and will instead induce disease
What are the characteristics of C. piliforme?
-gram-neg.
-causes Tyzzer’s disease in lab animals
-acute, fatal diarrhea and focal liver necrosis
-cannot be cultured
Which gram-negative non-spore forming anaerobe is of importance?
Fusobacterium necrophorum
What are the characteristics of Fusobacterium necrophorum?
mucosal membrane and skin commensal
-involved in liver abscess and foot rot
How is Fusobacterium necrophorum diagnosed?
-anaerobic culture
-PCR
How is Fusobacterium necrophorum treated?
antimicrobials
How is Fusobacterium necrophorum controlled?
-hygiene and management
-vx to prevent foot rot
