Actinomyces

Actinomycosis Dogs and cats

A. viscosus - Subcutaneous abcesses - Thoracic, abdominal, and retroperitoneal infections A. hordenovulneris - Associated with grass awn penetration/migration - Can also cause abcess of the liver, spleen, and septic arthritis

Nocardiosis diagnosis, treatment, and control

Diagnosis - Presumptive -- Clinical findings, identification of filamentous gram + parially acid-fast bacilli - Definative -- Culture and species ID via molecular methods, susceptibility testing important for treatment Treatment - Debridement and drainage of lesion - Prolonged administration of trimethoprim-sulfonamide Control - Hygiene and teat antisepsis - Isolation/culling - Chemical drying of affected quarters

Nocardiosis disease patterns

Ruminants - Mastitis -- swelling, hot, fibrotic and painful - Pneumonia, abortion rare Swine - Pneomonia, abortion, and lymphadenitis all rare Horses - Pneomonia, pleuritis, systemic abcesses, abortion Cats - Cutaneous-subcutaneous abcesses, trauma related - Pulmonary and disseminated forms less common Dogs - Pneumonia, pleuritis with emphysema, dissemination can occur - Cutaneous-subcutaneous forms less common

Nocardia spp.

- Branching filaments that fragment into rods and cocci - Partially acid-fast, Gram + - Saprophytes, cause opportunistic infections of immunodeficient hosts, via trauma to skin, teat canal, inhalation, ingestion, not contagious - Nocardiosis is characterized by suppurating lesions with various granulomatous features, saguinopurulent exudates, occasional soft granules - Readily spreads by hematogenous dissemination - Facultative intracellular organisms -- grow inside phagocytes, protected by virulence factors

Actinomycosis Diagnosis

- Clinical presentation - Sulfur granules in exudate - Gram stain - Culture is often negative and contains only associated bacteria, granules offer best chance of isolation - PCR improves chance of species ID

Dermatophilus congolensis

- Exudative dermatitis with crust formation -- trauma or persistent moisture facilitate invasion of epidermis and hair follicles - Enzyme virulence factors increase permeability of the epidermis - Crust formed by neutrophilic exudate, often painless, secondary infections can occur - Lesion progression: papules -- exudate -- painbrush lesions of matted hair - Can be diagnosed with prep from scab, definitive isolation via culture or PCR - Can resolve in dry weather, parenteral antibiotics in severe cases, topicals for horses following grooming - Minimize skin trauma and exposure to rain or ectoparasites

Morphology

- Gram + - Varies from coccoid to filamentous - Free living saprophytes, mutualists, commensals, pathogens - Actinomyces, Nocardia, Dermatophilus, Corynebacterium

Actinomycosis Treatment

- Lesion drainage - Prolonged antibiotic treatment - Debridement of bone lesion - Prevention through oral care, limiting rough forage, protection from grass awn

Actinomycosis Ruminants

- Lumpy jaw -- Supperative lesions of the soft tissue and bone of the lower jaw - Oteomyelitis leading to tooth loss and mandibular fractures - Pulmonary infection rare

Actinomycosis Horses

- Mandibular lymphadenopathy, mimics strangles - Fistulous withers and poll evil

Actinomycosis Swine

- Mastitis and ventral subQ lesions -- suckling trauma - Occasional infection of lungs, spleen, kidney, etc.

Corynebacterium spp.

- Pleomorphic bacilli, non-spore forming - Facultative anaerobes and aerobes, many are commensals - Tissue trauma generally precedes infection, supperative lesions

Actinomyces spp. Pathogenesis

- Pyogranulomatous reactions with fistulous tracts - Exudate contains sulfur granules

Corynebacterium pseudotuberculosis

- Species seen most often in animal infections, can survive in the environment for months - Facultative intracellular pathogen (phagocytes) - Multiplies at entry site, spreads to draining lymph nodes -- virulence factor phospholipase D - Abcesses form in lymph nodes of sheep and goats, chronic infection -- caseous lymphadenitis (CLA), external = superficial lymph nodes, skin, and subcutis (goats), internal = internal organs and lymph nodes (sheep) - Pectoral abcesses in horses, occasionally internal, ulcerative lymphagitis of the limbs least common - Diagnosis presumptive with clinical findings and confirmatory via molecular ID, internal form difficult to diagnose (radiography, serological antigen testing) - External abcesses drained, CLA and lymphagitis treated with long term antibiotics - Prevent by minimal skin trauma when shearing and separating adult males, reduce fly exposure, vaccinate sheep and goats

Actinomyces spp. Characteristics

- Typically rods or filamentous, often branching - Many are capnphilic - Most are commensals of mammals -- oral mucosa, tooth surfaces, other mucous membranes - Opportunitstic pathogens -- endogenous infection by trauma - Typically polymicrobial infections, increases pathogenicity by producing/maintaining anaerobic environment