Difference between revisions of "Actinomycetes"

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#REDIRECT[[:Category:Actinomycetes]]
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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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*Cause [[Peritoneal cavity - inflammatory#In dogs|peritonitis in dogs]] and [[Peritoneal cavity - inflammatory#In cattle|peritonitis in cattle]] and [[Peritoneal cavity - inflammatory#In pigs|peritonitis in pigs]]
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*''Micropolyspora faeni and Thermactinomyces vulgaris'' in [[Bronchi and bronchioles - inflammatory#Extrinsic Allergic Bronchio-alveolitis|Bovine Farmers Lung]]
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*''Thermactinomyces vulgaris'' may cause [[Bronchi and bronchioles - inflammatory#Chronic obstructive pulmonary disease (COPD)|COPD]]
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 +
 
 +
 
 +
 
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===Overview===
 +
 
 +
*Gram positive bacteria
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*Grow slowly on media and produce branching filaments
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*Opportunistic infections causing inflammatory responses and granulomatous reactions
 +
*Animal pathogens include ''Actinomyces, Arcanobacterium, Actinobaculum, Nocardia'' and ''Dermatophilus''
 +
 
 +
 
 +
===''Arcanobacterium, Actinomyces'' and ''Actinobaculum'' species===
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 +
*Non-motile, non-spore-forming bacteria
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*Anaerobic or facultative anaerobes
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*Grow on enriched media; non-acid fast
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*Colonise mucous membranes
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*Modified Ziehl-Neelson negative
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 +
 
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===''Arcanobacterium pyogenes''===
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*Characteristics:
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**Formerly known as ''Actinomyces pyogenes'' and ''Corynebacterium pyogenes''
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**Small facultatively anaerobic rod
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**Grows slowly on blood agar to produce small, white colonies surrounded by a zone of beta-haemolysis after 48 hours
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**Produces hazy haemolysis after 24 hours; pin-point colonies after 48 hours
 +
**Coryneform morphology, like Chinese characters; may be curved with slightly swollen ends
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**Found in nasopharyngeal mucosa and genital tract of cattle, sheep, pigs
 +
*Pathogenicity''
 +
**Opportunistic infections following injury or viral/mycoplasma infection in ruminants and pigs
 +
**Extracellular toxins including haemolysin, proteases, DNase and neurominidase
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**Haemolytic toxin, pyolysin, member of the thiol-activated cytolysins (pore-forming toxins); possibly cytotoxic to phagocytic cells; dermonecrotising activity
 +
*Clinical infections:
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**Suppurative infections
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**Abscesses especially in liver
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**Lymphadenitis, [[Bones - inflammatory#Osteomyelitis|osteomyelitis]], peritonitis and neural abscessation
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**Pyometra
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**Endometritis
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**Summer mastitis
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**Ovine foot disease
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**Arthritis
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**Umbilical infections
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**Suppurative pneumonia
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*Treatment:
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**Penicillin or broad spectrum antibiotics
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**Unclassified ''Actinomyces'' species isolated from closed cases of [[Bursae and Tendons - inflammatory#Poll Evil and Fistulous Withers|Poll Evil and Fistulous Withers]]
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 +
 
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===''Actinomyces''===
 +
 
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*Usually long filamentous branching Gram positive rods
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*Anaerobic or facultativlyy anaerobic and capnophilic
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*Live in nasopharyngeal and oral mucosa
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*Cause pyogranulomatous lesions
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**''Actinomyces bovis''
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***Found naturally in oral cavity of cattle
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***Prefers anaerobic conditions but not strict anaerobe
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***Entry of organism into tissues following trauma to the mucosa from rough feed or tooth eruption
 +
***Causes [[General Pathology - Chronic Inflammation#Granulomatous Inflammation|granulomatous inflammation]] of soft tissues and bone, causing [[Oral Cavity - Teeth#Mandibular Osteomyelitis|lumpy jaw]]
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***Usually invades mandible to cause [[Bones - inflammatory#Osteomyelitis|osteomyelitis]] and may extend to surrounding [[Muscles - inflammatory#Actinomycosis bovis|muscles]]
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***The lesions begins as a painless swelling of the affected bone
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***Swelling becomes more painful and enlarges over a number of weeks, gaining fistulous tracts which discharge pus
 +
***Organisms found in yellow sulphur granules
 +
***Club colony formation
 +
***Colonies adhere to agar media and are non-haemoltic
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***Surgical treatment possible when lesions are small
 +
***Prolonged parenteral penicillin treatment may be beneficial early in the disease
 +
**''Actinomyces viscosus''
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***Commensal of oral cavity of dogs and humans
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***Canine actinomycosis
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***Causes localised subcutaneous pyogranulomatous lesions and fibrovascular proliferation of peritoneal and pleural surfaces in dogs
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***Leads to [[Pleural cavity and membranes - inflammatory#Pyothorax (Thoracic empyema)|pyothorax]]
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***Respiratory distress
 +
***Cutaneous pustules in horses
 +
***Abortion in cattle
 +
***Rods contained in soft grey granules which release the organism when squashed
 +
***Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments
 +
***Grow in 10% carbon dioxide
 +
***Usually responds to penicillin
 +
**''Actinomyces hordeovulneris''
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***Organism found in seed heads of certain grasses
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***Colonies adhere to agar and are non-haemolytic
 +
***Filamentous, branching organisms
 +
***Cause cutaneous and visceral abscessation, pleuritis, peritonitis and arthritis in dogs
 +
 
 +
 
 +
===''Actinobaculum suis''===
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**Found in preputial mucosa of healthy boars
 +
**Anaerobic
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**Coryneform morphology
 +
**Produces urease
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**3mm diameter colonies with shiny raised centre and dull edge
 +
**Disease transmitted at coitus
 +
**Sows develop disease within 3-4 weeks of mating
 +
**Produces lesions in urinary tract of sows
 +
**Cystitis and pyelonephritis in sows
 +
**Anoreixa, arching of back, dysuria and haematuria
 +
**May be fatal
 +
 
 +
 
 +
===''Nocardia''===
 +
 
 +
*Facultative intracellular bacterium
 +
*Aerobic short branching rods
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*Non-motile
 +
*Spores from aerial filaments when cultured
 +
*Grow on Sabouraud dextrose agar
 +
*Cell wall contains mycolic acids (hence slightly acid fast)
 +
*''Nocardia asteroides''
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**Found in soil and decaying vegetation - saprophytic
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**Opportunistic infection of immunocompromised animals
 +
**Infection via inhalation, wounds or teat canal; also ingestion
 +
**Causes granulomatous lesions in animals
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**Canine nocardiosis: cutaneous pyogranulomas; [[Peritoneal cavity - inflammatory#In dogs|peritonitis]]; [[Bacterial infections#Nocardiosis|pleuritis]] and pyothorax; disseminated lesions
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**Cattle: chronic mastitis; abortion
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**Pigs: abortion
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**Sheep, goats, horses: wound infections; mastitis; pneumonia
 +
**Survives and multiplies in macrophages
 +
**Superoxide dismutase and catalase as well as a thick peptidoglycan wall prevent activity of phagocytes
 +
**Chronic, progressive disease
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**Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
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**Cell-mediated immunity required
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*''Nocardia farcinica'' causes bovine farcy
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===''Dermatophilus congolensis''===
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*Aerobic
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*Motile zoospores
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*No growth on Sabouraud dextrose agar
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*Found in scabs and in foci on skin of carrier animals

Revision as of 17:02, 17 February 2008

BACK TO INFECTIOUS AGENTS AND PARASITES
BACK TO BACTERIA



Overview

  • Gram positive bacteria
  • Grow slowly on media and produce branching filaments
  • Opportunistic infections causing inflammatory responses and granulomatous reactions
  • Animal pathogens include Actinomyces, Arcanobacterium, Actinobaculum, Nocardia and Dermatophilus


Arcanobacterium, Actinomyces and Actinobaculum species

  • Non-motile, non-spore-forming bacteria
  • Anaerobic or facultative anaerobes
  • Grow on enriched media; non-acid fast
  • Colonise mucous membranes
  • Modified Ziehl-Neelson negative


Arcanobacterium pyogenes

  • Characteristics:
    • Formerly known as Actinomyces pyogenes and Corynebacterium pyogenes
    • Small facultatively anaerobic rod
    • Grows slowly on blood agar to produce small, white colonies surrounded by a zone of beta-haemolysis after 48 hours
    • Produces hazy haemolysis after 24 hours; pin-point colonies after 48 hours
    • Coryneform morphology, like Chinese characters; may be curved with slightly swollen ends
    • Found in nasopharyngeal mucosa and genital tract of cattle, sheep, pigs
  • Pathogenicity
    • Opportunistic infections following injury or viral/mycoplasma infection in ruminants and pigs
    • Extracellular toxins including haemolysin, proteases, DNase and neurominidase
    • Haemolytic toxin, pyolysin, member of the thiol-activated cytolysins (pore-forming toxins); possibly cytotoxic to phagocytic cells; dermonecrotising activity
  • Clinical infections:
    • Suppurative infections
    • Abscesses especially in liver
    • Lymphadenitis, osteomyelitis, peritonitis and neural abscessation
    • Pyometra
    • Endometritis
    • Summer mastitis
    • Ovine foot disease
    • Arthritis
    • Umbilical infections
    • Suppurative pneumonia
  • Treatment:


Actinomyces

  • Usually long filamentous branching Gram positive rods
  • Anaerobic or facultativlyy anaerobic and capnophilic
  • Live in nasopharyngeal and oral mucosa
  • Cause pyogranulomatous lesions
    • Actinomyces bovis
      • Found naturally in oral cavity of cattle
      • Prefers anaerobic conditions but not strict anaerobe
      • Entry of organism into tissues following trauma to the mucosa from rough feed or tooth eruption
      • Causes granulomatous inflammation of soft tissues and bone, causing lumpy jaw
      • Usually invades mandible to cause osteomyelitis and may extend to surrounding muscles
      • The lesions begins as a painless swelling of the affected bone
      • Swelling becomes more painful and enlarges over a number of weeks, gaining fistulous tracts which discharge pus
      • Organisms found in yellow sulphur granules
      • Club colony formation
      • Colonies adhere to agar media and are non-haemoltic
      • Surgical treatment possible when lesions are small
      • Prolonged parenteral penicillin treatment may be beneficial early in the disease
    • Actinomyces viscosus
      • Commensal of oral cavity of dogs and humans
      • Canine actinomycosis
      • Causes localised subcutaneous pyogranulomatous lesions and fibrovascular proliferation of peritoneal and pleural surfaces in dogs
      • Leads to pyothorax
      • Respiratory distress
      • Cutaneous pustules in horses
      • Abortion in cattle
      • Rods contained in soft grey granules which release the organism when squashed
      • Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments
      • Grow in 10% carbon dioxide
      • Usually responds to penicillin
    • Actinomyces hordeovulneris
      • Organism found in seed heads of certain grasses
      • Colonies adhere to agar and are non-haemolytic
      • Filamentous, branching organisms
      • Cause cutaneous and visceral abscessation, pleuritis, peritonitis and arthritis in dogs


Actinobaculum suis

    • Found in preputial mucosa of healthy boars
    • Anaerobic
    • Coryneform morphology
    • Produces urease
    • 3mm diameter colonies with shiny raised centre and dull edge
    • Disease transmitted at coitus
    • Sows develop disease within 3-4 weeks of mating
    • Produces lesions in urinary tract of sows
    • Cystitis and pyelonephritis in sows
    • Anoreixa, arching of back, dysuria and haematuria
    • May be fatal


Nocardia

  • Facultative intracellular bacterium
  • Aerobic short branching rods
  • Non-motile
  • Spores from aerial filaments when cultured
  • Grow on Sabouraud dextrose agar
  • Cell wall contains mycolic acids (hence slightly acid fast)
  • Nocardia asteroides
    • Found in soil and decaying vegetation - saprophytic
    • Opportunistic infection of immunocompromised animals
    • Infection via inhalation, wounds or teat canal; also ingestion
    • Causes granulomatous lesions in animals
    • Canine nocardiosis: cutaneous pyogranulomas; peritonitis; pleuritis and pyothorax; disseminated lesions
    • Cattle: chronic mastitis; abortion
    • Pigs: abortion
    • Sheep, goats, horses: wound infections; mastitis; pneumonia
    • Survives and multiplies in macrophages
    • Superoxide dismutase and catalase as well as a thick peptidoglycan wall prevent activity of phagocytes
    • Chronic, progressive disease
    • Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
    • Cell-mediated immunity required
  • Nocardia farcinica causes bovine farcy


Dermatophilus congolensis

  • Aerobic
  • Motile zoospores
  • No growth on Sabouraud dextrose agar
  • Found in scabs and in foci on skin of carrier animals
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