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Bacteriology Unit 4
Terms in this set (252)
If a blood smear was done, these bacteria could be seen inside the RBCs but no lysed blood cells would be present.
Facultative intracellular pathogen of RBCs and endothelial cells.
Proliferative endovascular lesions caused by angiogenic factor is a distinguishing feature.
Clinical signs in an infected human would include fever, malaise, headache, and vesicular skin lesion.
Immunocompromised patients develop Bacillary Angiomatosis.
Secondary invader after respiratory viral infection in calves and young cattle and after infection of the naval in neonates.
Increased feeding of grain, which leads to rumen acidosis and rumenitis, would predispose a cow to infection by this organism.
Causes Necrobacillosis of the Liver
Causes Calf Diphtheria
Causes Thrush in horses.
Causes Foot Rot in cattle.
The main virulence determinant is pili, which allow adherence to epithelial cell in the interdigital epidermis.
Colonizes lesions initiated by Fusobacterium necrophorum.
Causes foot rot in sheep.
Does Burkholderia mallei or Burkholderia pseudomallei have a smaller genome?
Burkholderia mallei has a smaller genome.
Reservoir for Burkholderia pseudomallei
Causative agent of Glanders in equines.
Causative agent of Melioidosis.
This is the #1 cause of bacteremic pneumonia in SE Asia and Austrialia.
This is the main virulence factor for Burkholderia mallei and pseudomallei
Produces the blue pigment pyocyanin on nutrient agar.
Could you grow Pseudomonas aeruginosa on MacConkey agar?
No - because MacConkey is differential for gram neg and selective for lactose fermenters, and p. aeruginosa does not ferment lactose.
Why is pseudomonas aeruginosa so resistant so high levels of commonly used antibiotics?
Because of its efflux pumps and ability to form biofilms.
Reservoir for pseudomonas aeruginosa.
Wet soils and water, and commensal in healthy humans/animals
Virulence factors of Pseudomonas aeruginosa
Flagellum, extracellular toxin (NO CAPSULE)
Some Avibacterium species require ____ for growth (need special medium for isolation)
Will Pasteurellaceae grow on MacConkey agar?
Most WILL NOT
Causes shipping fever in cattle.
P. multocida, M. haemolytica
Causes fowl cholera in birds
Causes snuffles in rabbits.
Causes hemorrhagic septicemia in buffaloes
Causes atrophic rhinitis in pigs.
P. multocida, Bordetella bronchiseptica
Causes bite wound abscesses.
Causes coryza in chickens.
Causes swine pleuropneumonia.
Causes thromboembolic meningoencephalitis in cattle.
The only species of pasteurellaceae that does not have RTX toxin.
The ways RTX Toxin varies.
Size of toxin, number of glycine repeats, target cell specificity (RBC or WBC; species-specific WBC)
Cause of and two forms of disease of swine pleuropneumonia.
Caused by Actinobacillus pleuropneumonia. Two forms: Hemolytic dz (nose bleeds w/ consolidated lungs) and Necrotic dz (blue-tinged lungs w/ fibronecrotic lesions)
How many RTX genes are there in Actinobacillus pleuropneumoniae? How many of the genes does an isolate usually have.
At least 3 RTX genes. An isolate usually has 2/3.
Describe the different RTX genes.
Apx1: hemolytic and cytotoxic
Apx2: weakly hemolytic and moderately cytotoxic
Apx3: nonhemolytic and strongly cytotoxic
What happens if an isolate of Actinobacillus pleuropneumoniae loses one type of RTX toxin?
What happens if an isolate of Actinobacillus pleuropneumonia loses both RTX toxins.
Makes the isolate avirulent.
This is a commensal organism in the digestive tract of cattle and sheep, causing Wooden tongue in cattle and mammary abscesses in swine.
What makes the vaccine against Actinobacillus pleuropneumoniae protective?
Inactivated RTX toxin
Causes Shigellosis in foals.
Symptoms associated with infection by Actinobacillus equuli.
Infection of joints, infection of kidneys, diarrhea, peracute with rapid death.
Virulence factor of Actinobacillus equuli.
RTX toxin - hemolytic for equine leukocytes and RBCs
Virulence factors of Pasteurella multocida (2).
Hyaluronic acid capsule (type A- is antiphagocytic and has anti-complement activity), 2 types of sialidases (neuraminidases, mucolytic and provide nutrition)
Does pasteurella multocida have RTX toxin?
How many capsular serotypes are there of Pasteurella multocida?
How many O-antigen serotypes are there?
Causes Hemorrhagic Septicemia.
Causes fowl cholera in turkeys and chickens.
Is fowl cholera in turkeys, caused by Pasteurella multocida, usually chronic or acute?
Is fowl cholera in chickens, caused by Pasteurella multocida, usually chronic or acute?
Capsule serotype and O- antigen serotypes of the strain of Pasteurella multocida causing Fowl Cholera in turkeys.
Capsule serotype A; O antigen serotypes 3, 4, and 3x4
Capsule serotypes and O-antigen serotypes of the strain of Pasteurella multocida that causes Fowl Cholera in chickens
Capsule serotype A; O-antigen serotype 3 and 4 most common (but can be any type)
Causes Snuffles in rabbits.
A rabbit presents to you with abscesses on the joints, lungs, testicles, and skin, and respiratory infection. What do suspect is the culprit?
Pasteurella multocida, causing Snuffles, which is a chronic respiratory infection that also causes these chronic abscesses.
Can an infection by Pasteurella multocida in a rabbit be subclinical?
Yes, especially in research rabbits
What is the capsular serotype and O-antigen serotype in the strain of Pasteurella Multocida that causes Snuffles in rabbits?
Capsular serotype A; O-antigen type 12
How would Snuffles be diagnosed?
Through culture or serology - Sialidase ELISA (this is only available at the UGA D-lab)
Causes Atrophic Rhinitis in swine.
Virulence factor in the Pasteurella multocida strain that causes Atrophic rhinitis in swine.
Dermonecrotoxin (which stimulates bone resorption in the nasal turbinates)
You investigate a pig farm and notice the turbinates of the young pigs are soft, as if the bone is being resorbed. They all have facial deformity. What do you suspect is the problem.
Atrophic rhinitis caused by Pasteurella multocida and Bordetella bronchiseptica co-infection.
Capular serotype in the strain of Pasteurella multocida that causes Atrophic Rhinitis in swine.
Capsular serotype D.
Is Pasteurella multocida normal flora?
Yes - in the mouth of many animals
This is the leading cause of bite wound abscesses after a dog or cat bite.
Does Avibacterium endocarditidis have RTX toxin?
Of the Pasteurellaceae, which are zoonotic?
Those associated with bite wound abscesses, including Pasteurella multocida and Actinobacillus lignieresii
Explain the special culture technique required to grow Avibacterium paragallinarum.
NAD growth media, with cross streaking with Staph aureus.
Characterized by extensive polysaccharide capsule.
Is Haemophilus normal flora?
Yes - of upper respiratory tract.
You do a necropsy on a pig that died suddenly. You see inflamed serous membranes and joints, as well as extensive fibrin deposition covering the pleura. What are you thinking?
What insult is necessary for the endogenous spread of Haemophilus parasuis to the lower respiratory tract?
Respiratory viral infection
Key pathogenic features of Histophopholus somni?
Antigenic variation, immunoglobulin binding proteins (also can survive phagocytosis and will bind to/induce apoptosis.
How would a ruminant become infected with Histophilus somni?
Endogenous spread from the upper respiratory tract to the lungs or from the urogenital tract to the lungs. May become septicemia.
What predisposes an animal to infection by Histophilus somni?
Stress of weaning, whipping, cold weather; possibly viral infection is first insult
You are doing a post-mortem on a 7 mo old cow that has died along with 5 others. 3 cows have also aborted recently. You see foci of hemorrhage, thrombi formation, and necrosis in the brain associated with thrombotic meningoencephalitis. What do you suspect?
How can Histophilus somni be prevented?
Commercial vaccines for Histophilus or a vaccine to prevent viral diseases.
How is Taylorella transmitted?
Venereal transmission from an asymptomatic carrier stallion or mare. Indirect transmission through contaminated fomites, or through artificial insemination.
Your recently bred mare has purulent discharge coming from her vulva. The fetus also no longer has a heart beat. What do you suspect is the cause?
You have a mare that was infected with Taylorella last season. Can you breed her again?
Yes, but she needs to be checked if she is a carrier as some previously infected can become carriers. Contagious Equine Metritis caused by Taylorella equigenitalis is a self-limiting disease. It temporarily prevents conception. The uterine epithelium heals without long-lasting complications or effect.
Reservoir of Taylorella.
Carriers of previously infected mares, asymptomatic carrier stallions. Carried on external genitalia (urethra, urethral fossa, penile sheath of stallions, clitoral fossa of mares)
Is Taylorella a reportable disease?
What does Bordetella infect?
Ciliated respiratory epithelium
What is the reservoir for Bordetella?
Found in nasopharynx of healthy carrier animals.
How is Bordetella transmitted?
Inhalation of aerosols from diseased animal or carrier.
B. avium can be transmitted indirectly to poultry by exposure to contaminated litter and water.
What are the pathogenic features of Bordetella?
Adhesins, Dermonecrotic toxin, Adenylate cyclase/hemolysin, Tracheal cytotoxin, LPS, Pertussis Toxin
Adenylate cyclase causes dysregulation of cAMP control within the cell.
Dermonecrotoxin causes resorption of nasal turbinates.
Tracheal cytotoxin is highly inflammatory, causes cytokine release from immune cells that damage ciliated epithelial cells.
Pertussis Toxin is an ADP-ribosylating toxin that alters host protein function. It is only produced in the human pathogen but other species of Bordetella have the toxin gene in a mutated form.
Causes Kennel Cough or Infectious Tracheobronchitis in dogs.
Is Bordetella bronchiseptica zoonotic?
Yes (few reports, and most had no exposure to dogs)
Compare the severity of Bordetella bronchiseptica in cats than in dogs.
Can dogs catch Kennel Cough from cats? Can cats catch Kennel cough from dogs?
Yes and Yes!
How is Bordetella bronchiseptica transmitted in swine?
Transmitted from a carrier sow to her piglets.
What causes Progressive Atrophic Rhinitis in pigs?
Combined infection of Pasteurella multocida and Bordetella bronchiseptica.
Synergistic effects of dermonecrotoxin and toxigenic strains of P. multocida.
Are the effects of dermonecrotixin dose-dependent?
Yes - the more toxin present, the more resorption occurs of the nasal turbinates
What are the methods you could use to diagnose a fungal disease?
Direct microscopic exam of the tissue, Culture, Serological Tests, PCR
Two forms of fungi
Unicellular (yeast) and multicellular (hyphae)
What is a hypha?
Long filamentous cell of fungus, which becomes hyphae when it branches. Hypha is the mold-form.
What is mycelium?
Thick masses of hyphae.
Reservoir of fungus?
Is ubiquitous - solid is major reservoir.
What does it mean that fungi are saprophytes?
They acquire nutrients from dead or decaying organic matter
What is a dimorphic fungus?
Can exist as either mold or yeast, depending on environmental conditions.
What is a thermally dimorphic fungus?
Fungus that exists as a mold at a lower temp and when temp increases to over 35C will change to a yeast (as would be in vivo)
A thermally dimorphic fungus would be in this form in vivo.
How do yeasts reproduce?
Reproduce by asexual budding. Produce single cell growth.
What are conidia?
Spores of molds
How do molds and filamentous fungi reproduce?
Form conidia at the tips of the hyphae after a period of rapid growth.
Sexual reproduction in times of stress (likely occurs in nature, not animal)
What kind of growth does mold undergo?
Filamentous (hyphal) growth. As the hypha grows in length and beaches, the growth forms the mycelium (visible mass of hyphae).
A single fungal conidia will eventually form...
mycelium (conidia --> hypha --> hyphae --> mycelium)
Fungal cell wall compared to prokaryotic cell wall.
Describe the fungal cell wall and the purpose of each component.
Plasma membrane contains ergosterol. Chitin is next layer, which provides rigidity. Melanin present to resist oxidative stress from the host. 80% of the wall is made of complex polysaccharides: Glucan forms a triple helix that cross links and provides tensile strength. Mannoproteins are next row, make up 20% of cell wall.
How is the cell wall of a thermally dimorphic fungus different from one that is not thermally dimorphic?
The composition of the cell wall changes in the thermally dimorphic fungus. Beta(1-3) glycan is mainly present in the mold form, but not the yeast form.
What does infection by Bordetella bronchiseptica predispose the pigs to?
Causes Turkey Coryza.
You visit a turkey farm and notice sneezing, open-mouth breathing, and dyspnea in the population of young poults. Only a few have died. What do you suspect?
Turkey Coryza caused by Bordetella avium.
What causes Infectious Bovine Keratoconjuctivitis?
What are the pathogenic features of Moraxella?
Pilus (for adherence to conjunctival and corneal epithelial cells), LPS, and Cytotoxin (pore-forming or RTX type)
How is Moraxella bovis transmitted?
It is normal flora, and is also spread with flies during outbreaks.
How would you prevent Moraxella bovid outbreaks?
Control fly population (impregnate insecticide near ear tags), clip mature grasses to minimize corneal injury, Vaccine
What is the most common route of transmission of Francisella tularensis ssp. tularensis?
How is Francisella tularensis transmitted?
Direct contact with infected tissues, bite of infected arthropod (fly, tick), ingestion of contaminated raw milk or undercooked infected meat or contaminated water, inhalation of contaminated dusts/aerosols, or the bite of an infected animal.
What part of the world is Francisella only found in?
A good samaritan brings in a rabbit she easily caught in her yard that died on the way to the hospital. You do a necropsy and find oral ulcers, lymphadenopathy, and abscesses on the spleen and liver. What is the cause of death?
Tularemia caused by Francisella tularensis
A farmer calls you to report several of his sheep are sick. You find they have fever, low BCS, are coughing and breathing heavily. You do a necropsy on a lamb that has recently died and notice abscesses on the liver and spleen. You also remember that this area has a high tick burden. This farm is in the northern hemisphere. What is your diagnosis?
Tularemia caused by Francisella tularensis.
These food animals can be infected with Fransicella tularensis.
Sheep and Young pigs (Not reported in adult pigs or cattle)
Is there a vaccine available to prevent Tularemia in livestock?
This is one of the most infectious pathogens to people, requiring less than 10 bacteria to cause infection.
What are the forms of Francisella tularensis ssp. tularensis infection in humans? What is the most common form of infection?
Ulceroglandular form, pulmonary or respiratory form
Cause of chronic gastritis, stomach ulcers, gastric adenocarcinoma in people
Is Helicobacter normal flora?
Yes! In the stomach, intestinal tract, and liver of many species
What are the pathogenic features of Helicobacter pylori?
Flagella, Urease (hydrolyzes urea to ammonia to neutralize stomach acid), Vacuolating cytotoxin, LPS
What tool should you not use to collect fungal specimens from tissue?
Cotton swabs - poor recovery rate of fungus on the swab and cotton fibers can be mistaken for hyphae.
Is a gram stain a good tool to diagnose a fungus?
No - b/c most fungus will stain gram positive and the morphology can be distorted.
What types of tissue are usually appropriate to observe under a microscope?
Lung tissue, airway exudate. Sometimes, urine is appropriate.
What fungal medium is commonly used for culture?
Sabouraud's Dextrose Agar
What are some fungal elements that can be observed in clinical samples?
Hyphae, yeast, arthrospores
Can serology be used to diagnose all types of fungal diseases?
NO - only some fungal diseases
If using microscopy for diagnosis of a fungal disease, what is needed for visualization of fungal elements?
To find fungal elements in histophathological specimens, need special stains for visualization, such as Periodic Acid Schiff; Grocott's methenamine silver (hemotoxylin and eosin are not always useful).
What is Potassium Hydroxide used for when diagnosing fungal disease with microscopy?
Used to visualize fungal elements found on hairs or skin, such as dermatophyte arthrospores.
What is Lactophenol Cotton Blue used for when diagnosing fungal disease with microscopy?
Used to visualize fungal morphology.
What is India Ink used for when diagnosing fungal disease with microscopy?
Used to identify Cryptococcus neoformans because the capsule does not stain.
What does the fungal serological test detect?
Components of the cell wall, including galactomannan, beta(1-3)-D glucan, etc.
What is the pro and con of using a Histoplasma capsulatum antigen test?
Can sample any body fluid. The assay is sensitive, but it is not specific.
What does a positive result on a fungal serological assay indicate and what does it not?
Indicates systemic fungal infection.
Does not indicate which fungus is responsible.
Are fungi eukaryotic or prokaryotic?
Why are antibiotics not effective against fungi? What is the exception?
Because they target prokaryotic components. The exception: trimethoprim/sulfamethoxazole for tx of Pneumosystis carinii pneumonia
What problems do fungi pose regarding therapies?
It is difficult to target fungal cells without damaging the host cell (since both are eukaryotic). There are fewer anti fungal drugs than antibiotics. There is a problem of drug resistance.
How must an anti fungal be give in order for it to be effective?
Must be given long-term (for months)
What is the proper method of handling thermally dimorphic pathogenic fungi? Why?
Thermally dimorphic pathogenic fungi should be handled only inside a laboratory equipped with a biosafety cabinet.
Because the mold form is contagious (yeast form is not)
Can all fungi be cultured in the lab?
No - Dx by histopathology or PCR.
How could you determine if a fungus is thermally dimorphic?
If room temp culture of mold, change temp to 35-37C to see if mold form changes to yeast.
What is the basis of the diagnosis of a mold-forming fungus?
Based on the microscopic appearance of their conidia and conidiophores.
What is the mechanism of action of a polyene?
Binds to sterols (ergosterol) in the fungal plasma membrane, forms a pore...causes increased permeability of ions. Fungus swells and dies from osmosis.
The "old" Gold Standard for treating most anti fungal diseases in companion animals. Very cost-effective anti fungal therapy.
How must Amphotericin B be administered?
Intravenously - b/c polyenes are absorbed poorly if given orally.
What is the toxicity of Amphotericin B? What preparation makes this drug less toxic?
To proximal tubule epithelial cells in the kidney - causes cell death and leads to loss of renal function.
Preparation with liposomes is less toxic.
What is Nystatin?
What is the mechanism of action of Azoles?
Blocks ergosterol synthesis by inhibiting the enzyme required to convert lanosterol to ergosterol, which causes the buildup of toxic sterol (takes weeks for it to accumulate and begin killing susceptible fungus)
What makes azoles safer than polyenes?
They are not nephrotoxic.
What is the route of administration for azoles?
What is the mechanism of action of Allyamines?
Interferes with early step in ergosterol synthesis (inhibits enzyme squalene epoxidase)
What is the mechanism of action of Echinocandins?
Blocks beta(1-3)D-glucan synthase, which is an essential enzyme for beta(1-3)D glucan synthesis. This, in turn, inhibits the hyphal tip and brach point growth (is also active against some yeast)
What is the mechanism of Nikkomycin Z?
Blocks the synthesis of chitin (leads to fungi swelling and rupturing)
What is the mechanism of Griseofulvin?
Blocks mitosis of fungal cells (by binding to tubulin)
What type of infection is Griseofulvin used for?
How is Griseofulvin administered?
Orally (better absorption when given w/ fatty meal)
What is the mechanism of action of 5-fluorocytosine?
It is the fluorinated analogue of pyrimidine base cytosine.
It inhibits fungal DNA synthesis.
Which anti fungal is commonly given in conjunction with others? Why?
B/c resistance can rapidly develop.
This is the most cost-effective anti fungal drug.
Side effect of Iodide anti fungal.
What are dermatophytes? What is it colloquially called?
Molds that infect keratinized epidermal structures like skin, feathers, horns, hooves, claws, and nails.
Who is more susceptible to severe dermatophytosis?
How are dermatophytes transmitted?
Direct contact with infected animals or Indirect contact with fomites/environment
This preparation could be used to visualize an infection by a dermatophyte.
KOH - a prep that is used for fungi that invade the hair/skin. Dermatophytes invade via an arthrospore (or arthoconidium) that adheres to keratinized epithelium and germinates.
Pathogenesis of dermatophytes.
Arthrospore (arthoconidia) adheres to keratinized epithelium and enters via defect in the stratum corneum. Germination occurs and hyphae branch under the skin. Some of the hyphal growth will differentiate into arthroconidia as it contacts the hair follicles, and these arthroconidia will invade the hair shaft. Dermatophytes secrete enzymes to help them spread around epithelial cells and invade hair shafts. The hairs become brittle and break easily at the skin level. The arthrospores disperse and may survive up to 18 mo.
What do arthroconidia invade?
The hair shaft.
Most common causative agent of Canine Dermatophytosis.
Can you visualize micro or macroconidia in skin scrapings?
NO! can only visualize hatter growing on a lab medium.
What predisposes poultry to infection by Candida albicans?
, poor sanitation, overcrowding
What is the prognosis of Candidiasis that is systemic?
How would Candidiasis be treated?
Manage the underlying immunosuppressive disorder in addition to initiating anti fungal therapy.
What is a key stage in the pathogenesis of Sporydermatis schenckii?
It is phagocytksed by macrophages, which enables it to reach the lymph nodes and disseminate by lymphatic circulation.
Is Sporotrichosis zoonotic?
Yes! Wear gloves and wash hands w/ anti fungal.
Causes Rose Picker's disease in humans.
What is seen in microscopy that would lead to a diagnosis of sporotrichosis?
Cigar-shaped yeast in macrophages.
What is necessary for successful treatment of sporotrichosis?
Treat for 1 month after skin lesions have disappeared.
A cat comes into your clinic with severe ulcerative lesions. You see cigar-shaped yeast in macrophages under the microscope when you do a skin scrape. What is your diagnosis?
How is dimorphic fungus typically transmitted?
- the spores are inhaled and transform to yeast or an alternate form in the lungs.
What is necessary for the host's protection against dimorphic fungus? What happens if this is inadequate?
immunity - if inadequate, then dissemination throughout the body and
How does infection by dimorphic fungus present?
Lesions are _granulomatous_ or _pyogranulomatous_
Are vaccines commercially available for systemic dimorphic fungal diseases in humans or animals?
What does cryptococcus look like in a host?
What happens to the polysaccharide capsule of cryptococcus when it grows?
It is shed.
How does Cryptococcus enter the brain?
Though the cribiform plate.
Reservoir of Cryptococcus
What is not a useful diagnostic tool to use with Cryptococcus diagnosis? What is used instead?
Measuring antibody is not useful (b/c titers are low). Measure Cryptococcus antigen instead to detect
circulating capsule antigen in blood or CSF
How much Cryptococcus antigen titer is significant?
Most prevalent fungal infection of cats.
How would one treat cryptococcus?
surgical removal or fungal granulomas; long-term anti fungal tx w/ serology
How does treatment continue after a cryptococcus titer value is zero?
Treat for two months after
Reservoir of Histoplasma capsulatum.
Birds (that are asymptomatic carriers)
Most virulent fungus in US.
This fungus has a two-stage life cycle.
1) Saprophytic phase (arthroconidia - soil)
2) Parasitic Phase (spherules - in lung)
Are dogs infected with Coccidioides contagious?
Cause of Valley Fever.
Osteomyelitis associated with these fungal infections
Coccidiodes ssp. and Aspergillus terreus
What immune dysfunction is Aspergillosis associated with?
Decreased neutrophil function and number (neutropenia)
Usually, _________ kill the conidia of Aspergillus ssp and _____ kill the hyphae.
Alveolar macrophages; neutrophils
What is the source of infection of birds with Acute Avian Aspergillosis?
What is the source of infection of birds with Chronic Avian Aspergillosis?
Causes Guttural Pouch Mycosis.
What is the organism that causes canine nasal aspergillosis?
This fungal infection leads to the destruction of the nasal turbinate bones in dogs.
Aspergillus fumigatus - Canine Nasal Aspergillosis
What causes Canine Disseminate Aspergillosis?
What predisposes a dog to Canine Disseminate Aspergillosis?
Immunosuppression (and being a German Shepherd)
What is the primary symptom seen in Canine Disseminate Aspergillosis?
Also see granulomas in many organs
What is key to disease development with Pneumocystis carinii? What kind of foals would become infected?
Immunosuppression - Arabian foals with Severe Combined Immunodeficiency (SCID) (they don't have B or T cells)
What unconventional method is used to treat Pneumocystis carinii?
Trimethoprim/sulfa antibiotics and Echinocandins (b/c they target beta-glucans)
What makes Pneumocystis carinii different from other fungi?
It is obligate parasite, and does not have ergosterol.
What form does Pythium insidiosum grow on agar? When are the hyphae produced?
Mold grows on agar. Hyphae produced in vivo.
Is Pythium insidiosum a fungus?
No - it is similar. It has beta-glucan but no chitin or ergosterol.
Causes Swamp Cancer in dogs and horses.
This is most common form of equine pythiosis. How do they present clinically?
Cutaneous form. See presence of nodular lesions and draining tracts. See Kunkers (large yellowish gritty coral-like bodies found in lesions composed of eosinophils and Pythium hyphae)
What is the most common form of canine pythiosis?
A dog presents to you with draining lesions that the owner says have not been healing. The dog has been vomiting and has had diarrhea. When you ask about history, she tells you that they visited the Okefenokee Swamp a month ago, and her dog had a blast swimming there. What is your diagnosis?
Canine Pythiosis caused by Pythium Insidiosum.
Which two are not real fungus? Why not?
Pneumocystis carnii (does not have ergosterol) and Pythium insidiosum (does not have ergosterol or chitin)
What is a primary metabolite?
Produced as a result of normal nutrient metabolism and have a role in growth and development.
What is a secondary metabolite?
Don't have a role in growth and development, may function to establish environmental niche against competing microbes.
What are mycotoxins?
Highly toxic secondary metabolites. Intoxication occurs from ingestion of contaminated feed.
What is the most important factor in mold growth and mycotoxin production?
Optimal moisture is >13%
What is the mechanism of toxicity of Aflatoxin?
Damages liver - blocks RNA polymerase and thus mRNA formation. The activated form binds to DNA and causes DNA damage
Who is most susceptible to Aflatoxin toxicity? Who is most sensitive to Aflatoxin toxicity?
Younger animals are most susceptible. Monogastrics are most sensitive.
What makes dogs more susceptible to Aflatoxins than other species?
B/c they have less glutathione levels than other species, so not good at aflatoxin detoxification.
Ingestion of Aflatoxin by a bird can cause what?
This toxin mimics the activity of estrogen in gilts.
Mechanism of Trichothecenes.
Bind to ribosomes and inhibit protein synthesis.
Who is sensitive to tricothecenes?
All animal species are sensitive to trichothecenes.
Most prevalent mycotoxin.
Desocynivalenon (DON): Vomitoxin
Who are most sensitive to Fumonisins?
Horses and swine
What makes Fumonisins so bad to humans?
They are hepatotoxic, neurotoxic, and carcinogenic
What is the mechanism of action of Fumonisin?
Blocks enzymes involved in formation of intermediate lipid ceramide. (results in accumulation of sphinganine, has toxic effects)
Causes Moldy Corn Poisoning in horses.
Horse presents with blindness, circling, staggering, and seizures. Was fed moldy corn recently. What do you suspect?
Moldy Corn Poisoning - Fumonisin Toxicity
Where do ergot toxins come from?
You look for this structure when diagnosing a ergot toxicity.
Cow presents with sloughing of skin on ears and limbs. It is January. What do you suspect? Why?
- ergot alkaloid causes vasoconstriction of arterioles, which leads to reduced blood flow to extremities, and thus peripheral tissue sloughing.
-See this happening in the
are more likely to be exposed
What is required for mycotoxin detection in feed?
- must identify the mycotoxin, not just the toxigenic fungus
- Sampling is critical
- Specialized laboratory - ELISA immunoassays for rapid dx
Diagnosis through visualizing broad-based budding yeast in clinical sample.
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