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#REDIRECT[[:Category:Actinomycetes]]
 
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{{toplink
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|backcolour =
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|linkpage =Bacteria
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|linktext =BACTERIA
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|pagetype=Bugs
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<br>
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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 - Pathology#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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**[[Joints Inflammatory - Pathology#In Sheep|Arthritis]] of sheep post-dipping; [[Joints Inflammatory - Pathology#In Pigs|arthritis in pigs]] and [[Joints Inflammatory - Pathology#In Cattle|arthritis in cattle]]
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**Umbilical infections
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**[[Respiratory Bacterial Infections - Pathology#Acute exudative pneumonia|Acute exudative pneumonia]] and contributes to [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
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**May cause [[Muscles Inflammatory - Pathology#Abscesses|myositis]]
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**Unclassified ''Actinomyces'' species isolated from closed cases of [[Bursae and Tendons Inflammatory - Pathology#Poll Evil and Fistulous Withers|Poll Evil and Fistulous Withers]]
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*Treatment:
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**Penicillin or broad spectrum antibiotics
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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 [[Chronic Inflammation - Pathology#Granulomatous Inflammation|granulomatous inflammation]] of soft tissues and bone, causing [[Teeth - Pathology#Mandibular Osteomyelitis|lumpy jaw]]
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***Usually invades mandible to cause [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]] and may extend to surrounding [[Muscles Inflammatory - Pathology#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-haemolytic
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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 - Pathology#In dogs|peritonitis]]) and pleural surfaces in dogs
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***Leads to [[Pleural Cavity & Membranes Inflammatory - Pathology#Pyothorax (Thoracic empyema)|pyothorax]]
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***Respiratory distress
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***[[Bacterial skin infections - Pathology#Bacterial granulomatous dermatitis|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 [[Bacterial skin infections - Pathology#Bacterial granulomatous dermatitis|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, [[Bacterial skin infections - Pathology#bacterial granulomatous dermatitis|cutaneous]] and disseminated forms
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***Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
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***[[Peritoneal Cavity Inflammatory - Pathology#In dogs|peritonitis]]
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***[[Respiratory Bacterial Infections - Pathology#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 are 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 - WikiBlood|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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*[[Bacterial skin infections - Pathology#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 - Pathology#Extrinsic Allergic Bronchio-alveolitis|Bovine Farmers Lung]]
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*''Thermactinomyces vulgaris'' may cause [[Bronchi and Bronchioles Inflammatory - Pathology#Chronic obstructive pulmonary disease (COPD)|COPD]]
 
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