Difference between revisions of "Actinomycetes"

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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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#REDIRECT[[:Category:Actinomycetes]]
<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
 
 
 
 
 
 
 
 
===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, [[Bones - inflammatory#Osteomyelitis|osteomyelitis]], peritonitis and neural abscessation
 
**Pyometra
 
**Endometritis
 
**Summer mastitis
 
**Ovine foot disease
 
**Arthritis
 
**Umbilical infections
 
**[[Bacterial infections#Acute exudative pneumonia|Acute exudative pneumonia]] and contributes to [[Bacterial infections#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
 
**May cause [[Muscles - inflammatory#Abscesses|myositis]]
 
**Unclassified ''Actinomyces'' species isolated from closed cases of [[Bursae and Tendons - inflammatory#Poll Evil and Fistulous Withers|Poll Evil and Fistulous Withers]]
 
*Treatment:
 
**Penicillin or broad spectrum antibiotics
 
 
 
 
 
===''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 [[General Pathology - Chronic Inflammation#Granulomatous Inflammation|granulomatous inflammation]] of soft tissues and bone, causing [[Oral Cavity - Teeth#Mandibular Osteomyelitis|lumpy jaw]]
 
***Usually invades mandible to cause [[Bones - inflammatory#Osteomyelitis|osteomyelitis]] and may extend to surrounding [[Muscles - inflammatory#Actinomycosis bovis|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 ([[Peritoneal cavity - inflammatory#In dogs|peritonitis]]) and pleural surfaces in dogs
 
***Leads to [[Pleural cavity and membranes - inflammatory#Pyothorax (Thoracic empyema)|pyothorax]]
 
***Respiratory distress
 
***[[Bacterial skin infections#Bacterial granulomatous dermatitis|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 [[Bacterial skin infections#Bacterial granulomatous dermatitis|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:
 
***Thoracic, [[Bacterial skin infections#bacterial granulomatous dermatitis|cutaneous]] and disseminated forms
 
***Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
 
***[[Peritoneal cavity - inflammatory#In dogs|peritonitis]]
 
***[[Bacterial infections#Nocardiosis|pleuritis]] and pyothorax with fever, anorexia and respiratory distress
 
***Disseminated lesions
 
***Treat with appropriate systemic antibiotics for 6 weeks
 
**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
 
**Positive modified Ziehl-Neelson
 
**Culture on blood agar and incubate under aerobic conditions at 37 degrees centigrade for 10 days
 
**White, powdery colonies, adherent to the agar appear after 5 days
 
**Subculture onto Sabouraud dextrose agar yields wrinkled, orange colonies
 
**Lesions difficult to treat due to resistance of organisms to many antimicrobials (e.g. penicillins)
 
**Cell-mediated immunity required
 
*''Nocardia farcinica'' causes bovine farcy, a chronic infection of superficial lymphatic vessels and lymph nodes
 
 
 
===''Dermatophilus congolensis''===
 
 
 
*Filamentous, branching actinomycete
 
*Aerobic
 
*Produces motile zoospores
 
*No growth on Sabouraud dextrose agar
 
*Dermatophilosis most prevalent in tropical and subtropical regions
 
*Organisms found in scabs and in foci in skin of carrier animals
 
*Dormant zoospores become activated when moisture and temperature levels favourable
 
*Zoospores may survive 3 years in scabs
 
*'''Pathogenicity''':
 
**Does not usually invade healthy skin
 
**Entrance after trauma or persistent wetting
 
**Activated zoospores produce germ tubes which develop into filaments which invade the epidermis
 
**Invasion causes an accute inflammatory response with many neutrophils
 
**Microabscesses are formed in the skin
 
**Raised crusts develop in the affected regions
 
*[[Bacterial skin infections#Dermatophilosis|'''Pathology''']]
 
*'''Diagnosis''':
 
**Giemsa-stained smears from scabs reveal branching filaments containing zoospores
 
**Immunofluorescence
 
**Scab material can be cultured on blood agar at 37 degrees centigrade, 2.5-10% carbon dioxide for 5 days
 
**Zoospores can be cultured
 
**After incubation, colonies are yellow and haemolytic (after 48 hours); they later become rough and yellow, and gain a mucoid appearance
 
**No growth on Sabouraud dectrose agar
 
*'''Clinical infections''':
 
**Infection usually confined to epidermis
 
**Dermatophilosis
 
**Disease most prevalent in young animals
 
**Damage to the skin predisposes to infection; blood-sucking insects also thought to be involved in transmission
 
**Lesions after heavy rainfall predominantly affect dorsum of farm animals
 
**Papules, serous, exudative matting of hair, raised crusty scabs
 
**Scab formation more prominent in sheep and cattle than in horses
 
**Lesions may resolve within weeks if dry weather, or may progress
 
*'''Treatment''':
 
**Parenteral antibiotics e.g oxytetracycline, pr penicillin-streptomycin combinations
 
 
 
 
 
*''Micropolyspora faeni and Thermactinomyces vulgaris'' in [[Bronchi and bronchioles - inflammatory#Extrinsic Allergic Bronchio-alveolitis|Bovine Farmers Lung]]
 
*''Thermactinomyces vulgaris'' may cause [[Bronchi and bronchioles - inflammatory#Chronic obstructive pulmonary disease (COPD)|COPD]]
 

Latest revision as of 11:54, 10 May 2010