Exam 2: Dermatophilus, Nocardia, and Actinomyces Flashcards
What is Dermatophilus congolensis commonly called in cattle, goats, and horses?
Cutaneous streptothrichosis
What is Dermatophilus congolensis termed in sheep when the wooled areas of the body are affected?
Lumpy wool
What are 2 morphologic forms of Dermatophilus congolensis?
Filamentous hyphae and motile zoospores
What factors allow Dermatophilus congolensis to thrive?
Prolonged wetting by rain
High humidity
High temperature
Various ectoparasites
When do epidemics with Dermatophilus congolensis occur?
During the rainy season
What can spread an infection of Dermatophilus congolensis?
Shearing, dipping, introducing an infected animal into a herd or flock
What do zoospores of Dermatophilus congolensis do?
Germinate to produce hyphae, which penetrate into the living epidermis
What happens to the epithelium invaded by Dermatophilus congolensis?
It cornices and separates in the form of a scab
What do wet scabs do with Dermatophilus congolensis?
Enhances the proliferation and release of zoospores from hyphae
What is Dermatophilus congolensis most prevalent in?
The young animals chronically exposed to moisture and immunosuppressed hosts
What speeds the healing of infection from Dermatophilus congolensis?
Onset of dry weather
What are the primary economic consequences of Dermatophilus congolensis?
Damaged hides in cattle
Wool loss in sheep
Lameness and loss of performance in horses when severely affected around the pastern area
What are the 3 stages that lesions from Dermatophilus congolensis can be observed in cattle?
Hairs matted together as paint-brush lesions
Crust or scab formation as the initial lesions coalesce
Accumulations of cutaneous keratinized material forming wart-like lesions that are 0.5-2 cm
What do typical lesions from Dermatophilus congolensis consist of?
Raised, matted gifts of hair
What are chronic lumpy wool infections from Dermatophilus congolensis characterized by?
Pyramid-shaped masses of scab material bound to wool fibers
What are lesions from Dermatophilus congolensis on horses like?
Matted hair and paint-brush lesions leading to crust or scab formation with yellow-green pus present under larger scabs
What does histopathalogic exam of Dermatophilus congolensis reveal?
The characteristic branching hyphae with multidimensional spetations, coccoid cells, and zoospores in the epidermis
What are Dermatophilus congolensis organisms like in active lesions? Chronic lesions?
Usually abundant in active lesions
Sparse or absent in chronic lesions
What does the diagnosis of Dermatophilus congolensis depend on?
The appearance of lesions in clinically diseased animals and demonstration of Dermatophilus congolensis in stained smears or histologic sections from scaps
What is the most practical diagnostic test for Dermatophilus congolensis?
Cytologic examination of fresh crusts and/or impression smears of the underside of freshly avulsed lesions
How can Dermatophilus congolensis been seen?
Under oil immersion as 2-6 parallel rows of gram-positive cocci that look like railroad tracks
What antimicrobials is Dermatophilus congolensis susceptible to?
Erythromycin Spiramycin Penicillin G Ampicillin Chloramphenicol Streptomycin Amoxivillin Tetracyclines Novobiocin
How can chronic infections of Dermatophilus congolensis be cured?
With a single IM injection of procaine penicillin (22,000 IU/kg) and streptomycin (22 mg/kg)
How should lesions from Dermatophilus congolensis in horses be treated?
Theshould be gently soaked and removed
What is nocardia?
Gram-positive, strictly aerobic, nonmotile, pleomorphic, and nonsporeforming
Organisms in this genus mat take the form of rods, cocci, or diphtheroids, and they sometimes produce branching filaments and aerial hyphae
Most reduce nitrate, produce catalase, and oxidize sugars
Some are partially acid-fast
Where is nocarida commonly found?
Soil
Decaying vegetation
Compost
Other environmental sources
How does nocardia enter the body?
through contamination of wounds or by inhalation
What contributes to the virulence of nocardia?
Trehalose 6,6’-dimycolate
How does trehalose 6,6’-dimycolate contribute to virulence of nocardia?
By inhibiting phagosome-lysosome fusion
What in nocardia probably mediates resistance to killing by neutrophils?
Membrane-bound catalase and superoxide dismutase
What may be involved in the pathogenesis of nocardia?
A mouse-toxic secreted product of N. otitidiscaviarum
What is the first clinical sign of N. asteroides?
The appearance of an indurated nodule or pustule, which ruptures and suppurates
Where is infection of nocardia often found in cattle?
Draining tracts of mammary glands
What does nocardia cause when it disseminates from the mammary gland to other organs?
Suppurative pleurites or peritonitis
What does canine thoracic nocardiosis often involve?
Suppurative pleuritis and peritonitis
Abscessation of heart, liver, kidneys, and brain are common
What may occur with nocardia in hoses and pigs?
Nocardial abortion
What nocardia species has been isolated from supparative wounds?
N. brasiliensis
What nocardia species was named for its occurrence in guinea pig ear infections?
N. otitidiscaviarum
What nocardia species is associated with bovine farcy?
N. farcinica
What nocardia species cause granulomatous lesions in salmonid fish?
N. salmonicida and N. seriolae
What genus have nocardioform actinomycetes from placentitis and abortion in horses in some of areas of the US been placed in?
Crossiella, eg, C. equi
What can a presumptive diagnosis of nocardia be based on?
Pathology and the presence of gram-positive, acid-fast branching, beaded filaments in smears
What do colonies of nocradia do?
Adhere to the surface of blood or chocolate agar
What is the treatment for nocardia?
β-lactam antimicrobial agents are not therapeutically effective for any myocardial infection
Udder infusions of novobiocin, combined with nitrofurazone, for 305 days has been successful treatment of bovine nocardial mastitis
Nonmastitic forms can be treated with sulfamethoxazole-trimethoprim, sulfonamides, novobiocin, ampicillin, or tetracyclines
Describe actinomyces
Gram-positive, non-acid-fast rods, many of which are filamentous or branching
Braches are less than 1 μm in diameter, as opposed to fungal filaments, which are more than 1 μm in diameter
What is A. bovis the etiologic agent of?
Lumpy jaw in cattle
What has A. bovis been isolated from?
Abscesses in the lungs of cattle and from infrequent infections in sheep, pigs, dogs, and other mammals, including chronic fistulous withers and chronic poll evil in horses
What is lumpy jaw?
A chronic, progressive, indurated, granulomatous, suppurative abscess that most frequently involves the mandible, maxillae, or other bony tissues in the head
When is disease with A. bovis seen?
When it is introduced to underlying soft tissue, via penetrating wounds of the oral mucosa from wire or coarse hay or sticks
What can A. bovis result in when it is involved with adjacent bone?
Facial distortion
Loose teeth
Dyspnea
What indicates the presence of A. bovis?
Demonstration of gram-positive rods in yellowish “sulfur granules” rom aspirated purulent material
Why is treatment of A. bovis in cases where bone is extensively involved rarely successful?
Poor penetration of antibacterial agents
What can be effective in less advanced cases of A. bovis?
Penicillin
What was once successful for systemic treatment of A. bovis, but is no longer recommended due to food safety issues?
Potassium iodide
What does A. hordeovulneris cause?
Localized abscesses and systemic infections, such as pleuritis, peritonitis, visceral abscesses, and septic arthritis in dogs
What is a common predisposing factor to A. hordeovulneris?
Tissue-migrating foxtail grass
What is A. israelii primarily associated with?
Chronic granulomatous infection in humans, but has been isolated from pyogranulomatous lesions in pigs and cattle
What has A. naeslundii been isolated from?
Aborted pig fetuses
What has A. (Corynebacterium) pyogenes been reclassified as?
Arcanobacterium pyogenes
What was the genus of A. (Corynebacterium) pyogenes recently changed to? Why?
Trueperella
Genomic findings
What are conditions caused by A. (Corynebacterium) pyogenes?
Suppurative mastitis Suppurative pneumonia Septicemia Vegetative endocarditis Endometritis Septic arthritis Wound infections (umbilical infections, seminal vesiculitis, summer mastitis) Liver abscesses
What is the number 1 bacterium in the rumen and reticulum of ruminants and the intestines of pigs?
A. (Corynebacterium) pyogenes
What does A. suis cause?
Pyogranulomatous porcine mastitis
What is pyogranulomatous porcine mastitis characterized by?
Viscid, yellow pus surrounded by a wide zone of dense connective tissue
Yellow “sulfur granules” may be scattered throughout the pus
Deep seated abscesses may fistulate
What can pyogranulomatous infections caused by A. suis develop in?
Lungs
Spleen
Kidneys
What does A. viscosus cause?
Chronic pneumonia
Pyothorax
Localized subcutaneous abscesses in dogs
What are thoracic lesions by A. viscosus? Cutaneous lesions?
Pyogranulomas
Granulomatous abscesses
