BacT week 6 Flashcards
acid fast-partial bacteria
corynebacterium, rhodococcus, nocardia
acid fast bacteria
mycobacterium
Corynebacterium key characteristics
gram + pleomorphic bacteria. Aerobes or facultative anaerobes. short mycolic acids in cell wall.
Pathogenic strains are non-motile
Commensals found on mucus membranes, some species in environment. Often host-specific.
Opportunistic pathogens causing mainly pyogenic infections. Tissue trauma allows for establishment of pathogenic bacteria
Tend to survive in macrophages and cause chronic granulomatous disease
External lipid coat (mycolic acids) virulence factor
Corynebacterium. protection from hydrolytic enzymes in host phagocytes
exotoxin phospholipase D (PLD) virulence factor
Corynebacterium. Hydrolyze cell membranes to cause increased vascular permeability
Diphtheria toxin virulence factor
Corynebacterium. interferes with protein synthesis in cells
corynebacterium important species
C. pseudotuberculosis. Has 2 types: non-nitrate reducing and nitrate reducing.
Non = sheep/goats, causes caseous lymphadenitis
Nitrate reducing = horses, cattle. Causes ulcerative lymphangitis, abscesses
Caseous lymphadenitis
chronic pyogranulomatous infection of the LNs. Abscessation/enlargement of superficial or internal LNs. Infection spread by pus from ruptured abscesses/nasal/oral secretions.
Caseous necrosis of the LNs
Organism can survive for long periods in the environment.
Internal abscessation –> thin ewe syndrome
3 month incubation period
Not hot or painful
economic losses
Caseous lymphadenitis diagnosis
CS (abscess, weight loss), culture purulent material, radiographs/ultrasounds for internal abscesses
Serology - synergistic hemolysin inibition test (for PLD antibodies). Positive titers can indicate recent exposure, vaccination, resolved infection, active infection. Low titer does not rule out disease, do REPEAT samples
Caseous lymphadenitis control
not curable!
Only treat animals with emotional/genetic value
Isolate animals to easily-disinfected area. drain abscesses, surgical excision if possible. Iodine/bleach/chlorhex to disinfect. Use systemic antibiotics
Ideally, cull infected animals.
Commercial vaccine for sheep and goats (not recommended in flocks that have never had CL)
Ulcerative lymphangitis (pigeon fever, dry-land distemper)
Infectious, inflammatory condition of the cutaneous lymphatic system in lower limbs and chronic abscesses in pectoral and ventral region. swelling of chest or abdomen, fever, loss of appetite, lameness, deep subQ external abscesses.
Common in dry areas (cali)
Seasonal patterns 0 more prevalent in autumn and early winter.
Flies play a role in transmission
Bacteria enter through skin abrasions
Ulcerative lymphangitis treatment and prevention
T = long-term systemic antibiotic therapy with topical treatment P = isolation of infected horses, fly control and good sanitation
Contagious bovine pyelonephritis
inflammation of the urinary bladder that may ascend to the ureters to cause kidney infection.
Caused by C. renale group of bacteria
Reservoir: vulva, vagina in clinically normal carrier cows
Contributing factors: parturition stress, peak lactation, high protein diet, trauma to bladder/urethra
CS: fever, anorexia, painful urination, ammoniac odor of urine, acute ab pain, decreased rumen contractions and milk production
Murine pseudotuberculosis
lungs: suppurative pneumonia
Kidney, liver, heart: nodular lesions
Joints: arthritic lesions of pedal extremities
LNs: hyperplasia
Rhodococcus characteristics
occur as cocci or rods. aerobic soil saprophyte. non-motile. salmon-pink colonies. weakly acid-fast.
Opportunistic pathogens in young foals (under 6 months). facultative intracellular pathogen - survive in macrophages
R. equi risk factors
dry wether, high foal density, poor grass cover on paddocks, large number of horses on the farm
vapA virulence factor
R. equi. promotes surival in non-activated macrophages. encoded by plasmid
capsular polysaccharides virulence factor
R. equi. slows phagocytosis
Mycolic acids virulence factor
R. equi. slows phagocytosis
Suppurative bronchopneumonia in foals
bronchopneumonia and lung abscessation in foals 1-4 months of age. Infection occurs mostly within the first 2 weeks of life.
CS: fever, anorexia, diarrhea, cough, dyspnea
Hard to detect - slowly progressive
polysynovitis, intestinal and mesenteric abscesses, ulccerative colitis
Significant economic impact - mortality, prolonged treatment, prophylaxis expenisve
Suppurative bronchopneumonia diagnosis
thoracic auscultation and percussion- crackles and wheezes w/ asymmetric distribution
Ultrasonography of the thorax - nodular long lesions
Cytological exam of respiratory secretion - neutrophilic leukocytosis
Culture of transtracheal or broncheoalveolar wash samples
Suppurative bronchopneumonia treatment and prevention
T = prolonged Tx, combination therapy of macrolide antibiotics and rifampicin. Supportive therapy. P = hyperimmune serum, colostrum, dust control, no vaccine!
Nocardia general characteristics
pleomorphic bacteria. Cocci or rods with long branching filaments. strict aerobes. facultative intracellular bacterium. Non-motile, non-spore forming. partial acid-fast
Ubiquitous in soil and water, usually non pathogenic for immunocompetent individuals.
Nocardiosis forms in dogs
thoracic, cutaneous and disseminated
Nocardiosis forms in cattle
mastitis
Canine nocardiosis
thoracic form - fibrovascular proliferative reaction on pleura and accumulation of sanguinopurulent fluid in thoracic cavity
Cutaneous form - ulcer or granulomatous swelling
disseminated form - non-specific clinical signs depends on organ system affected
Infection mainly via inhalation, through skin wounds or ingestion
Classic sulfur granules in exudate
Bovine nocardial mastitis
chronic mastitis with multifocal fibrosis in affected glands. white clots intermittently in the milk. outbreaks associated with dry cow therapy. control is difficult but nocardial mastitis is usually sporadic
occasional systemic reaction
Actinomyces general characteristics
gram +, club-shaped rods and filamentous branching bacT. Facultative or strict anaerobes, require CO2 (capnophilic). Non-spore forming, non motile. Characteristic colonies growing in the centre of lesions surrounded by macrophages (sulfur granules). Outer perimeter of lesion looks granulomatous.
Actinomyces are commensals of the oral cavity, colonize nasopharynx and oral mucosa
actinomyces pathogenesis
disrupted oral mucosa, spread by direct extension to bones, chronic infection with bone lysis
Lumpy jaw in cattle (actinomyces)
Pyogranulomatous osteomyelitis. granulomatous lesions involving the mandible, maxillae and other bony tissues of the head
Bone infection causes facial distortion, loose teeth and dyspnea.
Predisposition = trauma in the oral cavity
Lumpy jaw diagnosis
CS: swelling of jaw with fistulous tracts discharging purulent exudate
microscopic exam with crushed granules from aspirates of unopened lesions
culture purulent material (capnophilic!)
radiograhy can be used to determine degree of bone destruction
Lumpy jaw treatment and control
treatment: susceptible to penicillin G and iodine, long term treatment with high dose penicillin, can be excised surgically if small and circumscribed
long-term therapy may fail as these lesions are chronic and walled off
Control: minimize risk of injury, remove foreign bodies
Dermatophilus general characteristics
gram +, filamentous branching bacteria, aerobic, motile asexual zoospores (create hyphae). Has a tram track appearance.
Hyphae penetrate into living epidermis and subsequently spread in all direction causing inflammation
only can attack abnormal/reduced skin barrier
Causes infection of traumatized/persistently wet skin with formation of scabs and crusts
obligate pathogen
Dermatophilus acute vs chronic infection
acute - 2-3 weeks long, heals spontaneously
Chronic - cornification of epithelium –> scabs –> moisture enhances proliferation and zoospore release
dermatophilosis pathogenesis
filaments colonize hair follicles and penetrate skin layers, inflammatory cell layer is formed under infected epidermis and keratinizes –> scab and crust formation –> accumulation of cutaneous keratinized material forming a wart like lesion and matted hair
Dermatophilosis diagnosis
CS, detection in stained smears or histology of scabs, cytology of fresh crusts with Giemsa
dermatophilosis treatment
parenterally administered anti-b’s, topical treatments less effective but may include chlorhex or iodine
dermatophilosis control
isolate clinically affected cows, provide shelter during prolonged rainfall, clear grazing areas of thorny plants, reduce tick infestation, prophylactic tetracycline use in endemic areas, control of intercurrent diseases
Trueperella general characteristics
gram + pleomorphic, facultative anaerobic and capnophilic, non-motile and non spore forming. found on mucosal membranes in GIT, UGT, resp tract in cattle and swine.
Opportunistic pathogen of cattle/sheep/swine.
Suppurative infection, prevalence is sporadic and governed by precipitating stress/trauma
Pyolysin
hemolytic toxin, cytotoxic for neutrophils and macrophages, dermatonecrotic and lethal for lab animals
found in trueperella
Summer mastitis
caused by trueperella.
mastitis of non-lactating cows and heifers during summer months. synergistic action with other bacteria. Transmission via the head fly (hydrotea irritans). affected area is swollen, hard, painful and hot. Udder secretion is thick and clotted with green/yellow pus
Trueperella diagnosis
smear and gram stain of purulent material
necropsy and isolation of bacteria
Trueperella treatment
penicillin G! reports of resistance
Trueperella prevention
prevent primary cause, no efficient vaccine
Actinobaculum
actinobaculum suis - gram + rods, anaerobes, non-motile, non-spore forming
Commensal organism in preputial diverticulum of boars, not in UGT of healthy sows, transmitted via coitus
porcine cystitis, pyelonephritis, anorexia, arched back, dysuria, haematuria
Potentially fatal (renal failure)
