Exam 1 Flashcards
(56 cards)
1
Q
What is an obligate pathogen?
A
One that if present causes disease. Example, Bordetella bronchiseptica.
Upper respiratory infection: Kennel cough - Bordetella bronchiseptica, Infectious coryza (chickens) Avibacterium paragallinarum, Strangles Streptococcus equi.
2
Q
How does the Establishment of infection occur?
A
- Encounter
- Entry
- Multiplication and spread
- Damage
- Outcome
Each event requires breach in the host-defense and the way a bacteria combats host-defense decides the outcome of the infection.
Infection in balance with immunity
Disease = bolus of infection * virulence/ host immunity
3
Q
Bacterial Shape and arrangement
A
Coccus: spheric Coccobacillus: longer spheric Bacillus: rod Vibrio: curved rod Spirillum: spirochete-like
4
Q
Terminology
A
Gram Staining
- Gram positive: purple. Retain crystal violet stain, thick peptidoglycan wall
- Gram negative: pink/red, do not retain the crystal violet stain. Thin peptidoglycan wall.
- Strain: genetic variant
- Serotype: serologically and antigenically distinct, like a subgroup.
- Serovar: synonym for serotype.
- Oxidase positive/negative: Positive (when the color changes to dark purple within 5-10 secs). Bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain, which oxidizes the test reagent. Mostly Aerobic bacteria.
- Catalase positive/negative: Some bacteria have the enzyme Catalase, which facilitates cellular detoxification, it neutralizes H2O2.
- Coagulase: clotting reaction. It clots plasma in the presence of its activator. As a result of coagulase-activator reaction, a substance similar to Thrombin is produce, which converts fibrinogen to fibrin. S. aereus is coagulase positive.
- CAMP test: (Christie–Atkins–Munch-Peterson) test to identify group B Beta-hemolytic streptoccocci. Zone of Co-hemolysis phenomenon on sheep blood agar.
- Blood agar: hemolytic activity detection
- MacConkey agar: selective and differential media for non-fastidious gram negative rods, particularly Pseudomonas spp. Gram-negative enteric bacteria and the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria.
5
Q
Clinical case example
A
- History, Physical exam
- Create a problem list
- What are the differentials?
- Diagnostic plan
- Treatment decision and prevention plan.
6
Q
Establishment of bacterial and fungal infections
A
Pathogen: organism that causes disease in an immunocompetent host
Pathogenicity: the ability of an organism to cause disease in an immunocompetent host
Virulence: is a relative measure of pathogenicity. For example, a highly virulent vs. weakly virulent strain of a pathogen.
7
Q
Virulence
Why do some animals develop disease while others do not?
A
Virulence can be measured in a few different ways
- ID50 or infectious dose 50: is the number of bacteria needed to cause an infection in 50% of exposed animals.
- LD50 or lethal dose 50: number of bacteria needed to cause death in 50% of exposed animals.
- MLD or minimum lethal dose: for example, MLD of botulinum toxin for mice is <0.01 ng (1mg would kill 100 billion mice).
- Differences in the susceptibilities of individual animals: for example, the ID50 is 1000 for one animal, but 10 for another.
- Differences in the immune status of the host: immunocompromised vs. immunocompetent
- Differences in the breed susceptibilities: some breed are predisposed to some diseases due to genetic differences.
8
Q
Definitions
A
-Infection: presence and replication of an obligate pathogen within a host, implies overt disease or capability of causing disease.
- Apparent infection: infection with overt disease.
- Acute: SHORT time course, outcome may be death, recovery or progression to chronic. Ex: E. coli in canine
- Chronic: PROLONGED time course. Ex: Tuberculosis - Inapparent infection: infection without the presence of overt disease, generally results in colonization
- Colonization: presence of an organism without clinical or subclinical disease. However, it is replicating. - Carrier infection: persistent infection with a pathogen that may have previously caused disease, may later progress to apparent infection, Ex: Anaplasma marginale in cattle
9
Q
Events in Establishment of Infection
1. Encounter
A
- Encounter: microorganism meets the host
- Begins at birth
- Challenge with exogenous organisms: possible outcomes:
- Most common: do not gain entry or eliminated
- Less common: colonize to form normal flora
- Very few cases: cause disease
* Disease is more of the exception than the rule* - All neonates receive immunologic protection at birth: example, ETEC (enterotoxigenic E. coli) in calves due to failure of passive transfer of IgG, also calves have receptors in intestine that allow organism to bind.
LATER ENCOUNTERS
-Exogenous: obtained from an external source. Ex, food-borne Salmonella infection.
Control: modification of external source in some way, disinfectants, decreased contact, etc. The goal is to eliminate from host tissue.
-Endogenous: due to normal flora that is present in or on the host’s body. Ex: Pseudomonas aeruginosa infection in immunosuppressed patients.
Control: difficult. The goal is to eliminate from tissue NOT from host.
- Entry: microorganism or toxin enters the host body
- Multiplication and spread: microorganism and or toxin multiplies and spreads inside the host.
- Damage: host’s immune response and damage due to invasion
10
Q
- Entry
A
Several routes: Inhalation, ingestion, etc.
A. Ingress: pathogen enters without crossing epithelial barrier. Inhalation, ingestion, infection of mucus membranes.
- Inhalation: protection by constitutive host defenses. Any kind of damage (cilia/mucus) predisposes to bacterial infection. Ex: BRSV M. hemolytica infection in cattle.
- Ingestion: High concentration of bacteria (resident microflora) competes with invader and prevent infection/colonization. Ex: Enterotoxigenic E. coli in calves.
- Direct infection of mucus membranes: Examples, conjunctivitis, UTI, Keratoconjunctivitis in cattle Moraxella bovis (pink eye)
B. Penetration: pathogen penetrates deeper into tissues
- Pathogen dependent: specific bacterial structures bind to receptors and facilitate penetration. These structures are considered virulence factors as they contribute to the virulence of the pathogen. Ex: S. aureus adhesins, invasins, toxins.
- Pathogen independent: vector-borne transmission, cathaters, blood transfusions.
11
Q
- Multiplication and spread
What determines multiplication and spread?
A
-Inoculum size: is a prime determinant in outcome of exposure.
-Surgical prep goal is to decrease or eliminate inoculum size. 99% of neutralization of 10^5 organism still leaves 10^3 organisms. Pseudomonas aeruginosa (non-pathogenic) at high dose 100 billion/L enough to overwhelm skin defenses and cause infection in immunocompetent people.
E. coli 0157:H7 is highly pathogenic, 10-100 organisms can cause serious illness.
- Incubation period: time between exposure and onset of disease/symptoms. During this time bacteria are multiplying to get large enough in number to cause disease.
- Nutritional requirements of bacteria: can become a limiting factor, most bacteria need iron. Host increases transferrin levels -binds free iron.
- Temperature: some organisms can’t grow at certain temperatures. Som ringworm fungi can’t survive at 37C
- Some bacteria spread via blood: bacterimia. Transient bacteria is common, but rapidly cleared by host’s immune defenses.
- Bacteria in blood may be cell-associated: Brucella abortus is found in monocytes, hidden to some extent from immune system.
- Some bacteria spread via lymphatics: Streptococcus equi spreads from tonsils to submandibular LN (results in strangles) and can spread to medialstinal LN (bastard stangles).
- Some bacteria spread via fascial plane: Pseudomonas aeruginosa is highly motile and spreads this way (Hot tub folliculitis).
12
Q
- Damage
A
Three ways microbes damage host
- Release of endotoxin: the constitutive part of gram negative cell wall. Also called Lipopolysaccharide (LPS) Lipid A component is responsible for endotoxin activity.*
- Action is non-specific and dose-dependent. It can have physiological and or pathological effects, very harmful at high dose levels. - Production of exotoxin: Secreted bacterial proteins, may be from gram positive or gram negative.
Have very specific and often different actions. Most are encoded by plasmids or bacteriophages. - Damaging hist response: Inflammation, immune scape, immunopathology.
-Inflammation: beneficial in moderation, but harmful in excess.
-Immune scape: Streptococcus pneumoniae or Klebsiella carry capsule.
Rickettsia escape from phagosome and Ehrlichia inhibit phago-lysosomal fusion.
Bacillus anthracis produces toxins that damage phagocytes.
-Immunopathology: Immune complexes- Purpura hemorrhagica (S. equi)
Granuloma formation- Rhodococcal pneumonia, Tuberculosis.
13
Q
Infections of the skin I-II
Anatomy of the skin
A
- Hair
- Sebaceous Gland
- Sensory nerve ending
- Epidermis
- Dermis
- Subcutaneous tissue
- Capillaries, sweat glad, muscle, fat, collagen, fibroblasts, arteriole.
Physical barriers:
- Hair/fur: prevent direct contact
- Stratum corneum: inert and impermeable layer
- Temperature and pH: too cold/unfavorable pH for optimal growth or many. Skin pH acidic in healthy tissue.
Chemical Barriers:
- Fatty acids: bacteriostatic
- Inorganic salts: high salt concentration
- Transferrins: bind iron needed for bacterial growth
Immunological defense
- Site for interactions between immune cells and antigens
- Prevent deeper invasion
Normal Flora
- Bacteria and fungi
- Protective
14
Q
Normal Flora of the Skin
A
Number and species affected by several factors, including:
-Hydration, general health, physical and chemical environment, salt-transferrin, other bacteria nutrients, antibiotic production.
Resident Flora
- Live and multiply in the skin (obligate parasites)
- Form a permanent population
- Cannot be eliminated
- Normally are harmless
- Examples: Coagulase-negative Staphylococcus, alpha-hemolytic Streptococcus, Micrococcus spp. etc.
Transient flora
- Acquired from environment or mucous membranes
- Most do NOT multiply efficiently on skin - just there
- Are transient - CAN be remove or eliminated
- May be involved in pathological processes as secondary invaders
- Examples: Coagulase-positive Staphylococcus, E. coli, Proteus, etc.
15
Q
Bacterial infections of the skin
A
A. Primary: Initiate and cause most of the pathology.
- Occur in otherwise “healthy” skin - predisposing factor, if any, is minor.
- Single bacterial species is dominant
- Characteristic disease pattern evident - consistent disease syndrome.
- Antibacterial therapy is effective - underlying problem is less significant.
- Grease pig disease: Staphylococcus hyicus
- Dematophilosis: Dermatophilus congolensis (horses). Train rail-like morphology.
B. Secondary: associated with other conditions or infections. They join the party later.
*Demodectic mange and Staphylococcus pseudintermedius causes pyoderma.
-Predisposing conditions for secondary skin infections: parasites, viruses, fungi, etc.
Other local predisposing factors: humidity, skin folds, systematic disease.
-Hypothyroidism, Cushing’s disease.
-Physical or chemical trauma: surgical incisions, catheter placement, etc.
-Immunosuppression, corticosteroid therapy.
16
Q
Diagnosis of Bacterial skin Infections
A
Bacterial Culture
- Must distinguish between colonization and infection.
- Identification of bacteria in primary and secondary infection is useful if also consider the presence of normal flora. Ex: isolation of Staphylococcus pseudintermedius alone is not enough.
Need Correlation
- History: predisposing (underlying) factors
- Clinical signs: Pustules, prulent exudate, crusts.
- Bacterial isolates: virulence
Diagnostic work up considerations
-Sampling for bacterial culture: Do not sample open tracts or erosions (use unopened pustule).
Punch biopsy of lesion - NOT into formalin for culture.
-Direct smears: Gram’s and Wright’s stains
Gram’s stain: number and type of bacteria, presumptive ID; initiation of therapy
Wright’s stain: presence/type inflammatory cells, degenerate neutrophils with bacteria within cell is indicative of infection
Histopathology and surgical biopsy
- When to biopsy: any dermatosis that is unresponsive to treatment for 3 weeks or any recurrent dermatosis
- Advantages of early biopsy: avoids nonspecific, masking, and misleading changes of chronicity; allows rapid institution of specific therapy.
- What to biopsy: intact pustules, take multiple biopsies, try to obtain primary lesions (avoid those marked by excoriation and chronicity).
17
Q
Classification of Skin Infections (Pyodermas = pus).
A
- Based on the depth of skin involvement: depth of infection
- Distinctions are clinically useful: deeper the lesions, more likely to be significant problem.
Surface Pyoderma: involves the epidermis only. Including intact hair follicles.
- Often sequelae to self-trauma or allergic skin disease. Examples, hot spots and early skin fold dermis.
- Pustules are present (mini abscesses)
- Recurrence is common and long-term management may be difficult.
- *Epidermis, maybe dermis
Deep Pyoderma: involves tissues deeper than hair follicles.
- Almost always secondary to other contributing factors
- Not common, but VERY difficult to treat.
- *Epidermis, dermis, and subcutaneous layer involvement**
18
Q
Infection of the Skin, Fungal
A
Dermatophytosis
Seborrheic dermatitis
Sporotrichosis
Phythiosis
19
Q
Dermatophytosis (Ringworm infections)
What genera causes the infection?
A
- Microsporum: 17 conventional species.
- The most significant are M. canis, M. gypseum, M. nanum and M. gallinae. - Trichophyton: 20 species, The most common are T. mentagrophytes, T. equinum, T. verrucosum.
- Epidermophyton: people
20
Q
Characteristics and other information about Microsporum canis and Trichophyton (dermatophytes).
- Hyphae: supports spore-bearing structures.
- Conidia: types of spores (asexual reproduction) formed on conidiophores.
- Sporangiospores: formed within sporangium
- *Mycoses: tissue invasion
A
- Large, rough, thick-walled multiseptae macroconidia (large multi-celled conidia).
- Macroconidia vary in shape from fusiform to a obavate.
- Microconidia are sessile or stalked, clavate, and usually arranged singly along the hyphae.
- M. canis: spindle-shaped
- M. gypseum: Boat-shaped
- M. nanum: Pear-shaped or ovoid macroconidium.
Trichophyton
- Macroconidia are cylindrical, clavate to cigar-shaped, usually thin-walled and smooth.
- Rarely produced and in small numbers
- Both genera attack skin, hair, nails, horns, and claws.
21
Q
Clinical signs of dermatophytosis
A
- Vary according to immune status of host and strain.
- Alopecia, erythema (abnormal redness of the skin), scaling, crusting, annular-ringed lesions, and vesicles or papules.
- Trichophyton spp. infections generally more severe due to inflammation.
22
Q
Canine ringworm
A
- Circular lesions up tp 2.5cm in diameter, commonly on face, elbows, and paws.
- Intense inflammation caused by T. mentagrophytes KERION, swelling, ulcerations, and purulent exudation.
- M. gyseum (compulsive burying of objects in soil)
- T. mentagrophytes (good rat catchers)
- T. erinacei (avid hedgehog-worriers)
23
Q
Feline Ringworm
A
- Usually caused by M. canis and cats are reservoirs.
- Often asymptomatic, public health risk.
- Cs: alopecia, mild scaling, folliculitis and generalized hair loss.
- Most common in kittens or immunocompromised
24
Q
Bovine Ringworm
A
- Common disease, calves most susceptible
- Incidence higher in winter
- Mostly Trichophyton verrucosum.
- Severe inflammation, pruritis, and secondary bacterial infection may occur.
- Spontaneous resolution of infection follows
25
Porcine ringworm
- large breeds most commonly affected
- Higher incidence due to humidity, stocking density, and poor sanitation
- M. nanum most common followed by M. gyseum, M. canis and T. mentagrophytes (geophilic).
- Lesions: located anywhere in body, circular, roughened, mildly inflamed, usually no loss of hair.
26
Equine ringworm
- Trichophyton equinum and M. gypseum most common
- Lesions: multiple dry scaly raised lesions on any part of body.
- Inflammation and production of exudates cause hair to mat together, and enlarged lesions create a moth-eaten appearance.
- infection often become chronic and subclinical, but recur during stress.
27
Ringworm of poultry
- M. gallinae
- Called 'favus' or "white comb"
- White patches in comb of infected males. May enlarge and coalesce to entire comb is thick and white.
- Occasionally spread to feathers
28
What is the more infective fungal stage?
- Spores are the major infectious form
- They are shed by infected animals in to the environment and may remain liable for months
- Transmission direct contact or by exposure to arthroconidia (arthrospores: spores formed during the process of hyphal fragmentation) in the environment or on fomites.
29
How does entry occur?
- Enters the skin through abrasions
- They do not invade or survive on living cells or areas of intense inflammation
- Spores germinate and the fungus grows on the stratum corneum of the skin and nails
- Crusty skin, bridle hair
30
How does multiplication occur? Spread?
- Virulence factors: proteases, keratinases and elastases
* **Infection with dermatophytes evokes intense inflammatory response. As a result fungal growth stops and moves to the next follicle. This continues and leads to circular lesions with a healing center***
- Most infections clear within weeks or months
31
Diagnosis
1. Wood's lamp examination of lesions.
- Not very sensitive (50-60%)
- Fluoresce green
2. Direct microscopic examination
- Use 10-20% KOH to examine hair and scales from lesions.
- Better results
- Ectothrix arthroconidia on hair
- Hyaline: clear, Dots outside hair: ectothrix
3. Culture: clean area with alcohol
- Hair clipped to quarter of an inch
- Sample from the periphery of a lesion
- scrape skin and pluck hair
- Dermatophyte test medium (DTM) for culture
32
DTM: dermatophyte test medium
Microscopic Morphology
- Cultures best incubated at 25C (spores, fungi) 37C, yeast form.
- T. verrucosum in cows 37C
- Growth in red slant before 10 days = dermatophyte
- Growth with yellow slant that turns red after 10 days = non-dermatophyte
- Dermatophytes utilize peptones in a DTM producing alkaline (RED) reaction.
- Most contaminant fungi utilize sugars first produce acid (yellow) then utilize protein (RED)
* *Nicotinic acid: required for T. equinum
* *Inositol and thiamine: T. verrucosum
Microscopic morphology
- Lactophenol cotton blue wet mounts of fungal growth
- Trichophyton may develop few macroconidia and are more difficult to identify
- Nutritional requirements, temperature tolerance, urase production, and in vitro hair perforation help identify Ectothrix.
33
Treatment, control and prevention
| Zoonotic Potential
-Removal of hair, shampoos, dips, sprays, topical antifungal.
Systematic:
- Griseofulvin
- Azoles: Ketoconazole, clotrimazole, and itraconazole.
- Terbinafine
- Treat until 3 negative weekly cultures.
Control and Prevention
- Clipping, topicals, sprays, etc.
- Clean up environment and fomites
- Wash bedding.
- 10% bleach solution
- Vaccination
Zoonotic potential
-Most common zoonoses: M. canis, T. verrucosum
34
Seborrheic dermatitis
Dogs
- Lipophilic yeast belonging to genus Malassezia (normally present in ears)
- Malassezia furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, M. dermatis, M. nana, and M. slooffiae.
- M. pachydermatis also causes OTITIS EXTERNA.
Encounter/entry
- Normal in cutaneous flora, anus, lips, skin, vagina, anal sacs, external ear canal of dogs.
- Opportunistic pathogen
- High humidity and excessive wax accumulation
- hairy and pendulous ears
- Neoplasm
- Allergies
- Change in quality or quantity of sebum; presence of other dermatoses.
- Recent antibiotic or glucocorticoid therapy
- Trauma
Clinical Signs
- Superficial: regionalized, face, feet, perineum, etc.
- Face rubbing, licking
- Skin erythematous and scaly
- Secondary alopecia and excoriation (when animal bites due to itch)
- Hyperpigmentation and lichenification with seborrhea as infection becomes chronic.
- Overgrowth due to predisposition factors (e.g., allergies, Seborrhea)
- Maybe allergic reaction to metabolic by-products of the yeast.
Diagnosis
- Consistent clinical signs
- Poor response to antibiotics, glucocorticoid and immunotherapy
- Demonstration of the typical yeast cells on skin scrapings or swabs
- SHOE PRINT or peanut-shape cells, impression smears.
Treatment and control
- Aimed at reducing number of organisms and identification plus removal of predisposing factors.
- Local/mild: selenium sulfide (shampoos), chlorhexidine, miconazole, ketoconazole.
- Systematic: ketoconazole, plus itraconazole daily
Zoonotic potential
- Malassezia pachydermatis is emerging zoonotic pathogen
- outbreak in neonatal care unit
35
Sporotrichosis
SUBCUTANEOUS
-Sporothrix schenckii: humans and animals affected.
Dogs
- Cutaneous, multicentric
- Lymphocutaneous: predominant syndrome, nodules along lymphatics
- Disseminated: rare, potentially fatal
* *Lesions begin at the point of entry and consists of subcutaneous nodules that ulcerate and heal.
- Disease may follow the course of lymphatic vessels and lymph nodes
- NOT PAINFUL NOT PRURITIC
Sporothrix schenkii
- Thermally dimorphic dematiaceous fungus
-Mold at 25C, yeast at 37C
-Most common in tropical and sub-tropical America
"Rose handler's disease"
-Isolated from soil, peat moss, and wood, vegetation.
IN HORSES
-cutaneous nodules that develop along the lymphatics, usually medial surface. 1-5cm in diameter and may ulcerate. Zoonotic
Encounter/Entry/Spread
- Conidia or mycelia through broken skin
- INSIDE the host: mycelial form changes to yeast form
- Lymphocutaneous manifestations, erythematous nodules at the site of entry
- Microabscesses and granulomas
- Spreads along lymphatics
- Regional lymph node may be involved
Virulence factors:
- Thermotolerance
- Acid phosphatase, proteinases I and II
- Adhesion to the host's body somewhere
Diagnosis
- Direct microscopic examination (feline specimens)
- exudate or aspirate from lesion
- Cigar-shaped yeast cells, may be seen in macrophages or extracellularly
- Lesions from cats tend to have large numbers of yeast cells.
- FAT on impression smears
- Cultures: 2-7 days Sabouraud dextrose agar at 25C. Mold colonies colored, wrinkled, leathery and turn black/grey with age.
- In brain-heart infusion agar 5% blood incubated 37C, 5-7% CO2 for 3-5 days. Yeast colonies are soft and white to cream colored
Treatment
- Iodide in humans and animals
- Azole also effective
- Cats sensitive to iodide, recommended itraconazole
- 3-4 mts for resolution
Zoonosis from cats: lesion exudates and feces contact
36
Pythiosis
- Chronic granulomatous disease
- Phytium insidiosum pathogen, fungal-like organism
- Lack chitin and ergosterol
- Gulf Coast states
- Horses and dogs most affected
Equine Pythiosis
(Bursatti, Swamp fever, leeches)
- Cutaneous and subcutaneous mycosis
- Limbs and ventral abdomen
- Ulcerative lesions
- Pruritic, discharge, mucosanguineous exudate, self-mutilation/trauma from itchiness.
- Lesions contain 'kunkers' or 'leeches' which are irregular, yellowish concretions that form in sinus tracts
- Necrotic coral-like seen inflammation Pythium insidiosum in horses
Diagnosis
- Direct exam and/or histopathology
- Large, hyaline, non-septate hyphae
- Culture needed for definitive diagnosis to distinguish from zygomycosis
- PCR, ELISA
- Lateral pegs or perpendicular branches
Treatment
- Radical excision is best, if possible
- Poor response to therapy
Caninie pythiosis
- GI disease, cutaneous, and subcutaneous
- Infiltrative pyrogranulomatous enteritis
- Subcutaneous lesions do occur in days
- Poor prognosis
- Surgical excision best
NO zoonotic potential
37
Buccal Cavity Infections
| What are the two buccal cavity infections and pathogens?
1. Wooden Tongue: antinobacillosis = soft tissue getting harder
2. Lumpy Jaw = antinomycosis = hard tissue getting softer.
38
Wooden Tongue
| What is the pathogen? Treatment? characteristics? Clinical signs?
-Soft tissue of mouth primarily in adult cattle, but sheep, pigs, horses and dogs can become infected
- Antinobacillus lignieresii
* *Gram Negative coccobacilli**
Clinical sigs
- Very hard, diffusely swollen tongue
- Excessive salivation
- Inability to prehend food normally
- Visible enlarged tongue that protrudes from the mouth
- On palpation, the tongue will feel very hard and it is painful
- Rare: large granulomas embedded in the tongue
- Pathogen is always present in the GI tract.
Encounter/Entry
- Part of normal mucosal flora upper GI tract
- Wound or trauma usually caused by straw or barley awns
Symptoms
- Localized infections, but can spread via lymphatics to other tissues.
- Can be confused with lumpy jaw
- Inability to prehend food
- Loss of condition
- May die from starvation
- Chronic infection may result in large abscesses with granules, creamy pus discharge
Diagnosis
- Clinical signs, lesions, history (rough feed)
- Confirmatory Dx: Culture, Gram-negative bacteria Rod.
- PCR, 16S gene
- MacCokey media growth
- Biochemical analysis
- Pus from abscesses crushed between two slides: club-like spicules of calcium phosphate.
- Granulomatous abscesses
- Club colonies (calcium phosphate around bacteria)
- No reliable serological tests
Antinobacillus lignieresii characteristics
- Gram negative
- Rod shape
- Facultative anaerobe
- Small, sticky, non-hemolytic colonies in BAP (blood agar plate)
Treatment
- Sodium iodide: IV 1-2 times per week.
- Systematic antibacterial: ceftiofur, penicillin, ampicillin, florfenical, and tetracyclines.
- Surgical removal of granulomatous if necessary
Prevention
-Avoid straw, coarse stemmy feedstuffs.
39
Lumpy Jaw = Antinomycosis = hard tissue getting softer
Pathogen: Actinomyces bovis
-It has also been isolated from nodular abscesses in the lungs of cattle, infrequently in other mammals
Clinical sigs
- Mandibular lesion of suppurative (formation and conversion to pus discharge )and proliferative osteomyelitis.
- Distortion, loose teeth (difficulty chewing), dyspnea from swelling into the nasal cavity
- At first lesion small growing, firm mass
- With or without drainage, purulent exudate
- Enlargement of the mandible
Encounter/Entry
- Actinomyces bovis: part of the normal flora of ruminants
- Via penetrating wounds from wire or coarse hay/sticks
- Gram positive
- Anaerobic bacteria
Diagnosis
- Based on clinical signs
- Gram-positive
- Culture from lesion sample
- Cytology
- Club-shaped rods filaments (sulfur granules)
- Radiography also useful
Treatment
- Sodium iodide: IV 1-2 per week
- Concurrent administration of oxytetracycline, penicillin or florfenicol recommended
Prevention
-Avoid course, rough, stemmy feedstufs
40
Wooden tonge vs. lumpy jaw
Wooden tongue:
- Gram negative
- Actinobacillus lignieresii
- Granulomatous abscesses
- Granules in exudates: greyish-white
- Club Colonies
- Spreads via lymphatics
- No bone involvement
- Facultative anaerobe
Lumpy Jaw
- Gram-positive
- Actinomyces bovis
- Bone involvement
- Jaw region
- Yellow 'sulphur' granules 1-3 mm
- No spread via lymphatics
- Anaerobic (O2 kills it)
41
Buccal cavity infections
Candida albicans
Aspergillus spp.
Fungal: Candidiasis, Aspergillosis
| -Necrotic stomatitis/pharyngitis bacterial
42
Candidiasis
- Localized mucocutaneous disease
- Pathogen: Candida albicans
Candida albicans
- Normal inhabitant of flora in nasopharynx, GI tract, and external genitalia.
- Opportunistic
Encounter/Entry
- Disruption of mucosal integrity
- Urinary catheters
- Antibiotic use
- Immunosuppression
**Most frequently in birds**
Thrush, Crop mycosis, Sour crop.
-Disease of GI tract in chickens, turkeys, young chicks and poults are most susceptible
Clinical signs
- Lesions in the crop
- Thickened mucosa
- Whitish, raised pseudomembranes
- Lesions in esophagus, mouth
- Swallow ulcers and sloughing of necrotic epithelium may be present
- Listlessness and inappetence
Control/Prevention/treatment
- Minimizing antibiotic use
- Nystatin and fluconazole Tx
Dogs and cats
- Exfoliative dermatitis
- Muzzle, inguinal area, scrotum, dorsal or lateral aspect of feet
- Otitis externa in foxhounds
- GI candidiasis associated with gastric ulceration in foals and calves
- Pigs cutaneous and mucocutaneous infection
Diagnosis
-Scrapings or biopsy specimens from mucocutaneous lesions
C. albicans
- Void, budding yeast cells with thin walls
- Pseudohyphae and true hyphae may be seen in the same specimen
- Culture in Sabourad's dextrose agar colonies white to cream color looks like Staph, but a lot larger.
- Culture 2-3 days at 25-30C
* *Germ tube test: differentiation from other Candida spp. Several colonies grown in animal serum at 37C for 3 hours = Short term tubes unique
- Biochemical and Molecular test commercially available
43
Aspergillosis
| Guttural pouch mycosis, infection of nasal and paranasal tissue
Pathogen: Aspergillus spp.
- A. fumigatus, A. terreus
- Primarily a respiratory infection
- Opportunistic
- Careful when taking samples, wear gloves
- Deep into tissue to get sample
Guttural Pouch mycosis
- Caudo-dorsal aspect of medial guttural pouch, over the internal carotid artery
- Damage to cranial nerves and the arteries within the mucosal lining of the pouch
- Mycotic plaques cause fungal erosion of the wall of internal and or external carotid arteries
- Hemorrhage is spontaneous and severe may be fatal
- Cranial nerves IX, X.
Aspergillus spp.
- Periodic acid-Schiff (PAS) stain
- Characteristic filamentous hyphae present in large numbers, biopsy.
Diagnosis
-Endoscopic examination of the guttural pouch
Treatment
-topical and systematic antifungal therapy, based on sensitivity testing
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Canine nasal Aspergillosis
- Can lead to bone loss
- The mucosa of the nasal and paranasal sinuses may be covered by a layer of gray-black necrotic material and fungal growth.
- Loss of bone definition on radiographs
- Lethargy, nasal pain, ulceration of the nares, sneezing, unilateral or bilateral sanguinopurulent nasal discharge, frontal sinus osteomyelitis and epistaxis (nose bleeding).
Diagnosis
- clinical signs
- Rhinoscopy - presence of fungal plaques
- Biopsy for histopathology or cytology and culture
- Radiology
- Microscopy of tissue samples : wet mount using KOH
* *Hyaline, septate hyphae that branch dichotomously with a 45 degree angle
- Easy to identify via characteristic conidial arrangement
- Remember that this is a ubiquitous and common fungus!!
- Phyloconidia: pretty bulbs
Treatment
-Topical azole (clotrimazole) delivered as 1-hour infusion
Health risk
-Immunosuppressed individuals at risk
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Necrotic stomatitis/laryngitis/pharyngitis
| Calf Diphtheria
- Infectious disease affecting pharynx, larynx, and oral cavity
- Pathogen: fusobacterium necrophorum
Fusobacterium necrophorum (gram-negative)
- part of the normal flora
- Inhabits mouth, intestines, genital tract of herbivores and omnivores.
- widespread in the environment
- Considered as a secondary invader
- Gains access through traumatic injury of the oral mucous membranes
- Diphtheria often occurs as necrotic dermatitis in calves <3mts of age
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Clinical sigs
-difficulty nursing
-Diarrhea
-Painful swallowing
-Odor in breath (necrotic stomatitis)
-Swollen cheeks
-Lump in neck
-Excessive salivation (necrotic stomatitis)
-Fever (necrotic stomatitis)
-Tachypnea
-Loud wheezing
-Pharyngeal edema
-Continuous bawling
Untreated calves usually die within 2-7 days from toxemia and pneumonia
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Diagnosis
- Based on clinical signs
- Lesions on necropsy identified
- Ulcers may extend into nasal cavity, trachea, or lungs
Fusobacterium necrophorum (gram-negative)
- Smear from deep tissue in the lesions
- Filamentous, beaded, gram-negative bacteria.
- culture in blood agar in anaerobic environment
- irregular staining, long, non-branching filamentous forms
Treatment
- sulfonamides or procaine penicillin G
- Flunixin meglumine or aspirin may be given to reduce fever and inflammation
- supportive care IV fluids, shelter, adequate ventilation.
- The prognosis is good if the infectious disease is detected very early and aggressive treatment is administered
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Eye and Ear Infections
Moraxella bovis (IBK: infectious bovine keratoconjuctivitis)
Moraxella bovoculi
Moraxella ovis
Infectious bovine keratoconjuctivitis (IBK) "Pink Eye or New Forest Disease"
-Pathogen: Moraxella bovis
Moraxella bovis
- Gram-negative rods, usually in pairs.
- Aerobic, non-motile
- Growth in enriched media
- Catalase positive and oxidase-positive
- Proteolytic (Hydrolysis of proteins), unreactive with sugar substrates.
- virulent strain are firmbriated and hemolytic
- Short-lived in environment
- Survives in salivary organs and on flies for 72 hours
- Age related immunity
- Asymptomatic carriers harbor M. bovis in nasolacrimal ducts, nasopharynx and vagina.
- Transmission via direct contact, aerosols, and through vector flies.
- Highly contagious
- Affects superficial structures of the eyes
- Affects mostly animal <2 years of age
- Causes economic losses
- Decreased weight gain
- Decreased milk production
- Short-term disruption of breeding programs
- Treatment costs
M. bovoculi
-Isolated from animals affected by IBK. Possess RTX toxin but pathogenicity unproven
M. ovis
-Isolated from a number of sites in farm animals but pathogenicity uncertain
Clinical Signs of IBK
- Blepharospasm, lacrimation, conjunctivitis, photophobia
- Keratitis, corneal opacity and ulceration; occasionally panophthalmitis and permanent blidness
- In mild cases cornea heals but there may be permanent scaring.
- Incidence lower in cattle with darker ocular pigmentation
Predisposing factors
- Age: <2 years of age
- Breed: Bos taurus
- Fly activity: increase vector activity
- Ocular irritants: dust, tall grasses, grass seeds, wind, cold ambient temperatures
- Concurrent infections: Herpesvirus 1 or Thelazia spp.
- Vitamin deficiency: Vitamin A
Virulence Factors:
- Fimbriae (Q fimbriae, I fimbriae): adherence to the cornea, stimulate type-specific protective immunity
- Hemolysin: (Mbx A) a calcium dependent, pore-forming cytolysin which damages the cell membrane of neutrophils. This is a RTX toxin with hemolytic and cytotoxic activity.
- Fribrolysin
- Phosphatase
- Hyaluronidase
- Aminopeptidase
Diagnosis
- Clinical signs
- Isolation of organism via cultural swabs or lacrimal secretions
- Organism is extremely fragile, so process samples quickly
- Blood and MacConkey agar: aerobically at 37C for 48-72 hours
- Rod small shiny friable colonies
- Catalase, oxidase positive; pitting of Loeffler's agar
M. bovoculi can be differentiated from M. bovis based on positive phenylalanine deaminase test
Treatment and control
- Use antimicrobials, prevention of ocular irritation
- Long-acting oxytetracycline at 72 hours apart
- Eye patches
- Control flies
- Vitamin A supplement
- Fimbriae-derived bacterins are of uncertain efficacy
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Otitis Externa
- Inflammation of the external ear canal
- Common problem in dogs and cats
Clinical signs
- head shaking
- Pain
- Malodor
- Erythema
- Erosion
- Ulceration
- Swelling
- Ceruminous gland inflammation
Diagnosis
- Otoscopic examination
- Cytology
- Culture
Primary cause
- allergy
- parasites (otodectes, demodex, sarcoptes)
- Autoimmune
- Foreign bodies
- Viral (distemper)
- Miscellaneous
Secondary causes
- Bacteria (Staphylococcus, Streptococcus, Enterococcus, Pseudomonas, etc.)
- Yeast: Malassezia
- Medication reactions
- Overcleaning
Predisposing factors
- Excessive moisture
- Systematic disease
- Conformation: excessive hair, pendulous pinna, etc.
- Obstructive ear disease
- Changes in normal flora
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Otitis externa in dogs due to Yeast infection
Pathogen: lipophilic yeast belonging to the genus Malassezia
-M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, M. dermatis, M. nana, M. slooffiae
***In dogs M. pachydermatis also causes Seborrheic dermatitis***
Clinical signs
- Head shaking
- Pruritis
- Odor
- In chronic cases, external ear canal may become filled with a thick waxy brown discharge
Encounter/Entry
- Malassezia spp. are part of normal flora
- Opportunistic pathogens
- Normally resides in skin, lips, anus, vagina, anal sacs, and external ear canal of dogs.
Predisposing factors
- High humidity and excessive wax accumulation
- Hairy and pendulous ears
- Neoplasm
- Allergies
- Change in quantity or quality of sebum; presence of other dermatoses; increased moisture
- Recent antibiotic or glucocorticoid therapy
- Trauma
Multiplication/Damage
-Overgrowth due to predisposing factors. Seborrhea, allergic reactions to metabolic by-products of the yeast.
Malassezia spp.
- Shoe-print or peanut-shaped cells
- Cytologic exam of affected areas (impression smears)
- Broad-based yeast cells, oval elongated.
Treatment and control
- Therapy to reduce number of organisms and identification
- Removal of predisposing factors
- Systematic disease: KETOCONAZOLE. Pulse administration and daily administration of itraconazole
**Diff-Quick stained smear can quickly determine whether microbial overgrowth is present
- Coccal organims usually staphylococcus or streptococcus
- Rod-shaped: Pseudomonas aeruginosa, E. coli, or Proteus mirabilis
- If a gram stain is not available, ulceration of the ear canal, a slimy green discharge, and cytology that shows rods only is highly suggestive of Pseudomonas infection
- Otitis externa with primarily gram-negative rod infection may also be associated with a particular pungent odor
- Polymyxin B and fluoroquinolone antibiotics have most successfully controlled Pseudomonas infections.
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Chlamydial Conjunctivitis
Pathogen
Chlamydiaceae family bacteria
- Intracellular bacteria
- GI tract, repro tract, conjunctiva
- Shedding usually from conjunctiva
- Spherical intracellular
- Unique developmental cycle
- Stain with MZN and Giemsa
- Energy parasites are able to synthesize ATP
- Cell walls lack peptidoglycan but contain LPS family specific
- Elementary bodies (EBs): Infectious extracellular form: small, metabolically inactive, NOT MULTIPLY.
- Reticulate bodies (RBs): Non-infectious intracellular reproductive: Large, metabolically active, MULTIPLY.
-Several members of the family: Chlamydia caviae guinea pigs, Chlamydia suis pigs, Chlamydia psittaci birds sheep, Chlamydia pecorum cattle sheep Most common cause of pink eye in sheep.
Clinical Signs
-Acute or chronic purulent inflammation of the conjunctiva with or without the presence of keratitis
Treatment
- Tetracycline-class antibiotics
- Systematic administration of antibiotics is preferred because infection may arise from or involve other anatomic sites.
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Feline Chlamydiosis
- Chlamydia felis (formely Chlamydia psittaci)
- Conjunctivitis and rhinitis (less common)
- Feline pneumonitis original name, rare lower respiratory tract infection
Epidemiology
- Direct contact or fomites
- Nasal secretions or conjunctival secretions
- May shed from repro tract
- Most susceptible <1 year of age
Clinical signs
- Incubation period ~ 5 days
- Uni or bilateral conjunctival congestion, clear ocular discharge
- Chemosis (swelling of the conjunctiva tissue around the cornea) and blepharospasm (involuntary winking) evident
- Secondary infection with Mycoplasma felis, Staphylococcus spp.
- Ocular discharge mucopurulent
- Conjunctivitis accompanied by sneezing and nasal discharge
- Resolves without treatment in a few weeks when animal is healthy
Diagnosis
- Conjunctival swab
- Giemsa-stained smears may reveal intracytoplasmatic inclusions
- Isolation of organism in cell lines or embryonated eggs
- RBs (reticular bodies) intracellular, non-infectious, metabolically active
- EBs (elementary bodies) extracellular, infectious, small. Not active.
- ELISA kits, lipopolysaccharide antigen
- Conventional and real-time PCR
- Complement fixation test, ELISA, immunofluorescent test to detect Chlamydia antibodies
Treatment
- Tetracyclines antibiotics of choice
- Live vaccines available reduce clinical effects but does not prevent infection
- Zoonotic, small number of cases from guinea pigs
- **Wear gloves**
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Guinea Pigs inclusion Conjunctivitis
- Chlamydia caviae
- Susceptible 1-2 mts of age
- Subclinical disease may occur
- Rhinitis, lower respiratory tract disease, genital infections causing salpingitis and cystitis in female guinea pigs, urethritis in males may also occur
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Leptospiral uveitis in horses
-Water-borne
Leptospira spp.
- Motile, tightly coiled spiral organism with hooked ends
- Gram-negative
- Stain poorly, need dark field or phase contrast microscope
- Serologically and epidemiologically diverse > 250 serovars
- Can persist in renal tubes or genital tract
- Worldwide zoonosis
- Carriers mice, asymptomatic
- Enter body through abraded skin or intact mucous membranes
- Humans infected via contact with infected urine
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Leptospiral uveitis
Inflammation
- Ciliary body
- Iris
- Choroid body
- Late complication = reversible or irreversible blindness in humans and horse
- Inflammation of the uveal tract of the eye; iris, ciliary body, choroid
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Human Leptospiral uveitis
- Weil 1886
- Acute and non-granulomatous pan-uveitis
- Timely treatment = good prognosis
- 10% of total uveitis endemic in India, one-third infectious cases
- Hypopyon and cataract
- Vitreous membranes attached to the dis
- Hyperemic disc with retinal vasculitis
- Retinal vasculitis
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Equine Recurrent Uveitis (ERU)
- Leptospira interrogans serovar POMONA is the most common in the US
- The Appaloosa breed and horses with MHC class I haplotype ELA-A9 increased risk
Pathogenesis
- Autoimmune responses to ocular tissue components play a significant role in pathogenesis
- Antigenic relationship between equine lens and L. interrogans components has been suggested
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Which leptospiral proteins are expressed in the eye? what do they do?
- LruA, LruB: lens proteins identified to react with antisera raised against LruA and LruB
- They may cross-react with resulting antibodies, leading to inflammation and or disruption of protein function "MOLECULAR MIMICRY" damages eye
Diagnosis
- Microscopic Agglutination test (MAT): Gold standard, paired samples
- PCR (targeting lipl32) very sensitive and specific.
- IHC and Dark-field: low sensitivity
- Culture: requires special media and takes several weeks
