|
|
| (16 intermediate revisions by 4 users not shown) |
| Line 1: |
Line 1: |
| − | <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>
| |
| − | | |
| − |
| |
| − | | |
| − | | |
| − | ===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 - Pathology#Osteomyelitis|osteomyelitis]], peritonitis and neural abscessation
| |
| − | **Pyometra
| |
| − | **Endometritis
| |
| − | **Summer mastitis
| |
| − | **Ovine foot disease
| |
| − | **[[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]]
| |
| − | **Umbilical infections
| |
| − | **[[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]]
| |
| − | **May cause [[Muscles Inflammatory - Pathology#Abscesses|myositis]]
| |
| − | **Unclassified ''Actinomyces'' species isolated from closed cases of [[Bursae and Tendons Inflammatory - Pathology#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 [[Teeth - Pathology#Mandibular Osteomyelitis|lumpy jaw]]
| |
| − | ***Usually invades mandible to cause [[Bones Inflammatory - Pathology#Osteomyelitis|osteomyelitis]] and may extend to surrounding [[Muscles Inflammatory - Pathology#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 - Pathology#In dogs|peritonitis]]) and pleural surfaces in dogs
| |
| − | ***Leads to [[Pleural Cavity & Membranes Inflammatory - Pathology#Pyothorax (Thoracic empyema)|pyothorax]]
| |
| − | ***Respiratory distress
| |
| − | ***[[Bacterial skin infections - Pathology#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 - Pathology#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 - Pathology#bacterial granulomatous dermatitis|cutaneous]] and disseminated forms
| |
| − | ***Cutaneous pyogranulomas: ulcers or granulomatous swellings with discharging fistulae
| |
| − | ***[[Peritoneal Cavity Inflammatory - Pathology#In dogs|peritonitis]]
| |
| − | ***[[Respiratory Bacterial Infections - Pathology#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 - Pathology#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 [[BronBronchi and Bronchioles Inflammatory - Pathology#Extrinsic Allergic Bronchio-alveolitis|Bovine Farmers Lung]]
| |
| − | *''Thermactinomyces vulgaris'' may cause [[Bronchi and Bronchioles Inflammatory - Pathology#Chronic obstructive pulmonary disease (COPD)|COPD]]
| |