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| − | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
| + | #REDIRECT[[:Category:Actinomycetes]] |
| − | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
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| − | ===Overview===
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| − | *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
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| − | *Animal pathogens include ''Actinomyces, Arcanobacterium, Actinobaculum, Nocardia'' and ''Dermatophilus''
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| − | ===''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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| − | ===''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
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| − | **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
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| − | *Pathogenicity''
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| − | **Opportunistic infections following injury or viral/mycoplasma infection in ruminants and pigs
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| − | **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
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| − | *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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| − | **[[Bacterial infections#Acute exudative pneumonia|Acute exudative pneumonia]] and contributes to [[Bacterial infections#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
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| − | **May cause [[Muscles - inflammatory#Abscesses|myositis]]
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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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| − | ===''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
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| − | ***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
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| − | ***Organisms found in yellow sulphur granules
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| − | ***Club colony formation
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| − | ***Colonies adhere to agar media and are non-haemoltic
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| − | ***Surgical treatment possible when lesions are small
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| − | ***Prolonged parenteral penicillin treatment may be beneficial early in the disease
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| − | **''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 ([[Peritoneal cavity - inflammatory#In dogs|peritonitis]]) 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
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| − | ***Cutaneous pustules in horses
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| − | ***Abortion in cattle
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| − | ***Rods contained in soft grey granules which release the organism when squashed
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| − | ***Two types of colonies: large and smooth colonies with V, Y and T configurations or small and rough colonies with short branching filaments
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| − | ***Grow in 10% carbon dioxide
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| − | ***Usually responds to penicillin
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| − | **''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
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| − | ***Filamentous, branching organisms
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| − | ***Cause cutaneous and visceral abscessation, pleuritis, peritonitis and arthritis in dogs
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| − | ===''Actinobaculum suis''===
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| − | *Found in preputial mucosa of healthy boars
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| − | *Anaerobic
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| − | *Coryneform morphology
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| − | *Produces urease
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| − | *3mm diameter colonies with shiny raised centre and dull edge
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| − | *Disease transmitted at coitus
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| − | *Sows develop disease within 3-4 weeks of mating
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| − | *Produces lesions in urinary tract of sows
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| − | *Cystitis and pyelonephritis in sows
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| − | *Anoreixa, arching of back, dysuria and haematuria
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| − | *May be fatal
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| − | ===''Nocardia''===
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| − | *Facultative intracellular bacterium
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| − | *Aerobic short branching rods
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| − | *Non-motile
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| − | *Spores from aerial filaments when cultured
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| − | *Grow on Sabouraud dextrose agar
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| − | *Cell wall contains mycolic acids (hence slightly acid fast)
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| − | *''Nocardia asteroides''
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| − | **Found in soil and decaying vegetation - saprophytic
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| − | **Opportunistic infection of immunocompromised animals
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| − | **Infection via inhalation, wounds or teat canal; also ingestion
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| − | **Causes granulomatous lesions in animals
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| − | **Canine nocardiosis:
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| − | ***Thoracic, cutaneous and disseminated forms
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| − | ***Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
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| − | ***[[Peritoneal cavity - inflammatory#In dogs|peritonitis]]
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| − | ***[[Bacterial infections#Nocardiosis|pleuritis]] and pyothorax with fever, anorexia and respiratory distress
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| − | ***Disseminated lesions
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| − | ***Treat with appropriate systemic antibiotics for 6 weeks
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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
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| − | **Survives and multiplies in macrophages
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| − | **Superoxide dismutase and catalase as well as a thick peptidoglycan wall prevent activity of phagocytes
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| − | **Chronic, progressive disease
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| − | **Positive modified Ziehl-Neelson
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| − | **Culture on blood agar and incubate under aerobic conditions at 37 degrees centigrade for 10 days
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| − | **White, powdery colonies, adherent to the agar appear after 5 days
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| − | **Subculture onto Sabouraud dextrose agar yields wrinkled, orange colonies
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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, a chronic infection of superficial lymphatic vessels and lymph nodes
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| − | ===''Dermatophilus congolensis''===
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| − | *Filamentous, branching actinomycete
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| − | *Aerobic
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| − | *Produces motile zoospores
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| − | *No growth on Sabouraud dextrose agar
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| − | *Dermatophilosis most prevalent in tropical and subtropical regions
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| − | *Organisms found in scabs and in foci in skin of carrier animals
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| − | *Dormant zoospores become activated when moisture and temperature levels favourable
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| − | *Zoospores may survive 3 years in scabs
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| − | *'''Pathogenicity''':
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| − | **Does not usually invade healthy skin
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| − | **Entrance after trauma or persistent wetting
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| − | **Activated zoospores produce germ tubes which develop into filaments which invade the epidermis
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| − | **Invasion causes an accute inflammatory response with many neutrophils
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| − | **Microabscesses are formed in the skin
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| − | **Raised crusts develop in the affected regions
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| − | *[[Skin - infectious#Dermatophilosis|'''Pathology''']]
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| − | *'''Diagnosis''':
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| − | **Giemsa-stained smears from scabs reveal branching filaments containing zoospores
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| − | **Immunofluorescence
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| − | **Scab material can be cultured on blood agar at 37 degrees centigrade, 2.5-10% carbon dioxide for 5 days
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| − | **Zoospores can be cultured
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| − | **After incubation, colonies are yellow and haemolytic (after 48 hours); they later become rough and yellow, and gain a mucoid appearance
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| − | **No growth on Sabouraud dectrose agar
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| − | *'''Clinical infections''':
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| − | **Infection usually confined to epidermis
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| − | **Dermatophilosis
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| − | **Disease most prevalent in young animals
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| − | **Damage to the skin predisposes to infection; blood-sucking insects also thought to be involved in transmission
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| − | **Lesions after heavy rainfall predominantly affect dorsum of farm animals
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| − | **Papules, serous, exudative matting of hair, raised crusty scabs
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| − | **Scab formation more prominent in sheep and cattle than in horses
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| − | **Lesions may resolve within weeks if dry weather, or may progress
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| − | *'''Treatment''':
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| − | **Parenteral antibiotics e.g oxytetracycline, pr penicillin-streptomycin combinations
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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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