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Bacteriology > Mycoses > Flashcards

Mycoses Flashcards

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1
Q

Sporangiospore

A

fungal spore formed by asexual reproduction. formed within a sporangium on an aerial hyphae called a sporangiophore

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2
Q

Conidia

A

fungal spore formed by asexual reproduction. formed on conidiophore

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3
Q

Zygospore

A

fungal spore from sexual reproduction. Develops in thick-walled zygosporangium, formed from the fusion of side projections of two compatible hyphae

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4
Q

Geophilic dermatophyte

A

dermatophyte that inhabits soil in association with decomposing keratinous material

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5
Q

Zoophilic dermatophyte

A

obligate pathogen in animals

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6
Q

Anthropophilic dermatophyte

A

obligate pathogen of humans

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7
Q

Dermatophyte important causal agents

A

Microsporum, Trichosporum, Epidermophyton

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8
Q

Microsporum general characteristics

A

invades hair and skin
thick-walled, multi-septated macroconidia
microconidia are stalked, clavate or arranged singly along hyphae
M. canis most common in domestic animals

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9
Q

Trichophyton general characteristics

A

Invades hair, skin, nails, horns, claws

Thin walled and smooth macroconidia, cylindrical to cigar shaped. Typically more severe than Microsporum infections

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10
Q

Dermatophytosis clinical signs

A

alopecia, erythema, scaling, crusting, annular-ringed lesions, vesicles or papules

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11
Q

Dermatophytosis transmission

A
  1. Arthrospores shed by infected animals are viable in the environment (months to years)
  2. direct contact with infected animal
  3. exposure to arthrospores in the environment/fomites
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12
Q

Dermatophytosis pathogenesis

A

Dermatophytes –> enter stratum corneum –> release proteases –> cause inflammation –> movement away from site of infection to nearby follicle –> central healing causes ringed lesion

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13
Q

Canine ringworm genuses

A

M. canis, M. gypseum, T. erinaceid, T. mentagrophytes

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14
Q

Canine ringworm lesions

A

brittle hair, dry and scaly skin, crusts and scabs

Kerion –> specific lesion due to T. mentagrophytes (intense inflammation, swelling, ulceration, prurulent exudate)

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15
Q

Canine predispositions to ringworm

A

Compulsive diggers (gypseum), good rat catchers (mentagrophytes), avid hedgehod worries (erinaceid)

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16
Q

Feline ringworm

A

M. canis –> main genus, cats are reservoir
Often asymptomatic (public health risk)
Lesions: circular areas of stubbed hair, alopecia, mild scaling and folliculitis at the head
Most common in kittens with immature immune systems and adults with immune deficiencies.

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17
Q

Feline otitis

A

persistent waxy, ceruminous, otic discharge caused by M. canis

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18
Q

Bovine ringworm

A

Trichophyton verrucosum.
Calves are more susceptible and incidence is higher in winter.
Lesions: circular, scattered, accompanied by skin scaling and alopecia, large plaques may develop with the formation of thick scabs and crusts, severe inflammation, pruritus (secondary bacT infections?)
Spontaneous resolution

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19
Q

Porcine ringworm

A

Microsporum nanum
Common disease, affects large breeds. Higher incidence with high density and humidity, poor sanitation
Lesions: circular, roughened, mildly inflamed. anywhere on body

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20
Q

Equine ringworm

A

T. equinum, M. gypseum
Lesions: multiple, dry, scaly, raised lesions on any body part. Inflammation and exudates cause hair to mat together and enlarged lesions create a moth-eaten appearance
Infections often become chronic and subclinical and recur under stress

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21
Q

Avian ringworm/favus/white comb

A

M. gallinae
Lesions: white patches on the comb of infected male birds
Occasionally, disease spreads into the feathers

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22
Q

Wood’s lamp

A

dermatophytosis diagnostic technique - 50-60% of M. canis infections test positive under UV light. Use fluorescing hairs for sampling

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23
Q

Direct microscopic exam for dermatophytosis

A

examine hairs from lesions/scales. Use 10-20% KOH. Fine hyaline septate hyphae in keratin scales and in hair shafts. Arthroconidia see on hair.

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24
Q

Dermatophyte Test Medium (DTM)

A

Growth with red slant before 10 days - dermatophyte
Growth with yellow slant that turns red after 10 days - non dermatophyte.
Medium provides peptones for protein, antibiotics, dextrose sugar, cyclohexamide to inhibit sapprophytes
Incubate at 25-30 degrees

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25
M. canis on culture
spreading whitish and cottony surface. Golden-yellow reverse pigment.
26
Physiological tests for dermatophytes
temperature tolerance, urease production, in vitro hair perforation test for Trichophyton
27
Treatment for dermatophytes
remove/kill fungus from skin/hair (clip, shampoos, dips, sprays, topical antifungals). Systemic therapy: azoles Treat until 3 negative cultures
28
control/prevention for dermatophytes
clean up environment and fomite sources (vacuum, wash bedding, etc.) use 10% bleach solution. Vaccination is effective for bovine ringworm.
29
Zoonotic dermatophytes
M. canis and T. verrucosum
30
Dermatomycoses important causal agents
Malassezia, trichosporon, geotrichum candidum
31
Malassezia
M. pachydermatis | lipophilic yeast, opportunistic pathogen (part of normal microbiome on the skin)
32
Otitis externa (malassezia)
clinical signs: head shaking, pruritus, bad odour, chronic otitis Diagnosis: otoscopic exam of ear canal, cytology for bacteria, yeast and mites Treatment: treat predisposing factors, topical antifungals and systemic antimicrobials
33
Seborrheic dermatitis (definition + CS)
superficial dermatitis as a regional disease affecting ventral abdomen, face, feet, neck. perineum, leg folds or generalized disorder Clinical signs: face rubbing, foot licking, erythematous skin, scaly skin, alopecia, hyperpigmentation, lichenification
34
Seborrheic dermatitis predispositions
breed: poodles, spaniels, chihuahuas, german shepherds, boxers, basset hounds others: allergies, seborrhea
35
Seborrheic dermatitis diagnosis, treatment
history of poor response to therapies, demonstration of yeast on skin scrapes (rule-out system). Most useful is cytology of affected areas looking for slightly elongated, oval, broad-based yeast Treatment: remove predisposing factors, shampoo/creams/dips with selenium sulfide/ketoconazole, oral ketoconazole
36
Trichosporon
causes nasal mass in cats. Treatment is to remove the mass surgically and follow up with oral ketoconazole
37
Geotrichum candidum
more found in exotic animals. Often isolated from feces of healthy/clinically normal animals. Causes cutaneous lesions, nodular, well-circumscribed dermo-epidermal masses
38
subcutaneous mycoses general characteristics
infections of deep skin, muscle, bone or CT. Associated with injured tissues. Etiologic agents: soil/decaying vegetation, dematiaceous or hyaline molds and dimoprhic fungi infections are chronic
39
Important causative agents of subcutaneous mycoses
Sporothrix schenckii, histoplasma capsulatum var. farciminosum, dermatiaceous fungi
40
Sporotrichosis characteristics
dimorphic, dermatiaceous. yeast at 37 degrees - cigar shaped, pleiomorphic budding yeast. mold at 25 degrees - thin septate hyphae with conidia in a rosette-cluster found in soil, vegetation, peat moss and wood Conidia enter the skin through puncture wounds from thorns or bites
41
Sporotrichosis geography
most common in in tropical and subtropical america
42
Sporotrichosis lesions
subcutaneous nodules that ulcerate and heal. lesions are not painful or pruritic. Disease may follow lymphatic vessels
43
Sporotrichosis CS in dogs
Cutaneous: localized, multicentric Lymphocutaneous: nodules along lymphatics Disseminated: rare, possibly fatal
44
Sporotrichosis pathogenesis
conidia or mycelia enter through broken skin --> change from mycelial form to yeast or parasitic form --> virulence factors (thermotolerance, acid phosphatases, proteinases) --> lymphocutaneous manifestation --> infection spreads along lymphatics
45
Diagnosing sporotrichosis with LM
Under LM: look for yeast (in macrophages). Cat lesions tend to have more yeast
46
Diagnosing sporotrichosis with culture
mold colonies are cream coloured, wrinkled and leathery. Will turn black/grey with age. Yeast colonies are soft and white to cream coloured
47
Sporotrichosis treatment
Iodide (not for cats), azoles, Itraconazole for cats
48
Sporotricosis zoonosis
most human cases occur through shedding from cats (scratch, bite). Prophylaxis: care in handling rote wood, plant material and infected animals
49
Epizootic lymphangitis
Histoplasma capsulatum var. farciminosum Dimorphic fungus. Yeast: pear shaped, double contoured budding yeast in macrophages/neutrophils Can be isolated from soil enriched with bird or bat feces Infection acquired by wound infection or transmission by blood sucking insects
50
Epizootic lymphangitis host
equids
51
Epizootic lymphangitis lesions
granulomatous, nodular lesions with a tendency to ulcerate in skin, subcutaneous tissue, along lymph vessels
52
Chromoblastomycosis
chronic fungal infection in cats and humans. Dermatiaceous fungi form thick walled-muriform cells (sclerotic bodies). CS: firm, protuberant, warty, ulcerative nodules (on feet and legs)
53
Eumycotic mycetoma
Limited to one area of the body. CS: swelling, fistulas, grains or granules in exudate. SubQ swellings with draining tracts, may resemble chronic abscess. Chronic mycetoma -- fistulous tumour may cause osteomyelitis
54
Phaeohyphomycosis
saprophytic, pigmented fungi that appear in lesions as dematiacous, septate hyphal forms (no granules). Found in dogs and cats CS: pustules, abscesses, granulomas, shallow ulcerated or open lesions
55
Bovine nasal granuloma
Granulomatous swellings in the nasal cavity and trachea of cattle. CS: dyspnea, inspiratory stridor, nasal discharge. Pink-white polyps visible on endoscopy
56
Bovine nasal granuloma diagnosis
direct exam of crushed polyp -- dematiaceous fungi | culture -- white colonies that become olive green, brown or black with dark reverse pigment
57
systemic mycoses primary SOI
lungs
58
systemic mycoses important causative agents
Blastomyces dermatitidis (dimorphic), coccidioides immitis (dimorphic), histoplasma capsulatum var. capsulatum (dimorphic), cryptococcus neoformans (yeast)
59
Blastomycosis
Blastomyces dermatitidis. Affects cats, dogs, humans Moves from lungs to skin, eyes and bones
60
Blastomycosis lesions
few to numerous, variable sized, irregular, firm, grey to yellow areas of pulmonary consolidation and nodules in lungs and thoracic lymph nodes Cutaneous lwesions -- single or multiple papules or chronic draining, nodular pyogranulomas
61
Blastomycosis pathogenesis
Aerosolized mycelial fragments or spores from the environment are inhaled. These are deposited in alveoli of a susceptible host. The mature yeast develop and grow intracellularly as large budding yeast. May spread from the lungs via lymph/blood vessels
62
Blastomycosis distribution
Highly endemic in North America --> Ohio, missouri, tennessee, mississippi river valleys, st. lawrence river area, great lakes
63
Blastomycosis clinical signs
coughing, dyspnea, dry and harsh lung sounds, anorexia, depression, lameness, lymphadenopathy, skin lesions (predominant in cats), ocular lesions
64
Blastomycosis diagnosis
clinical signs, history. Samples: tissues, tracheal wash, lymph node biopsy, cutaneous lesion exudate or biopsy Microscopy: spherical, thick walled, large, broad-based budding yeast Culture: mold culture is severe biohazard
65
Blastomycosis treatment
Itraconazole for dogs, amphotericin B for chronic/tough cases
66
Blastomycosis zoonosis
zoonotic transmission is uncommon but can happen from contaminated knives or dog bites. PPE important!
67
Coccidiomycosis (San Joaquin Valley Fever)
Coccidioides immitis. Dust-borne, not contagious Humans, dogs, llamas affected Primarily a chronic respiratory disease can spread to eyes, bones and joints Not zoonotic, but can mycelial phase can form on bandages of draining lesions
68
Coccidiomycosis pathogenesis
Arthroconidia in the environment mature into mycelia which fragment into arthrospores. Infection is via inhalation of arthrospore which causes transition into a spherule. spherule matures with production and release of endospores. Endospores will travel in lymph/blood
69
Coccidiomycosis distribution
Infections are in semi-arid regions of the SW USA (arizona, california, new mexico, texas, utah, nevada) and sikmilar areas of central and south america
70
Coccidiomycosis clinical signs
anorexia, cough, weight loss, lameness, abscesses, draining tracts, lymphadenopathy, meningitis
71
Coccidiomycosis diagnosis
CS and history Samples - draining lesions and biopsies or fine-needle aspirate of infected tissue (ook for classic spherules Culture - mycelial form very hard to handle. Mold have hyaline hyphae and alternating, barrel-shaped arthroconidia
72
Coccidiomycosis treatment
long term treatment (8-12 weeks) with azoles, amphotericin B if needed
73
Histoplasmosis
Histoplasma capsulatum var. capsulatum chronic, non-contagious, disseminated, granulomatous disease of humans and animals mainly in dogs and cats under 4
74
Histoplasmosis lesions
enlarged liver, spleen and mesenteric lymph nodes. Ascites, yellow-white variable-sized, granulomatous nodules in the lungs enlarged bronchial LNs, foci of granulomatous inflammation on liver, myocardium and SI
75
Histoplasmosis pathogenesis
inhalation or ingestion of microconidia or hyphal fragment from environment, conversion to yeast in vivo, yeast replicate, may spread via lymph/blood to spleen, bone marrow
76
Histoplasmosis distribution
humid environments with highly nitrogenous soils (contaminated with bird/bat shit). High risk areas: bat caves, old chicken houses Regions: tennessee, ohio, mississippi, missouri, st lawrence river area
77
Histoplasmosis clinical signs
pulmonary infection predominant, chronic disease (inappetance, weight loss, fever), enlarged LNs, anemia, GI problems in dogs
78
Histoplasmosis diagnosis
clinical signs and history samples: buffy coat smear, LN aspirate, rectal scraping, biopsies, bone marrow aspirate. Yeast are small in macrophages, basophilic center and clear halo Cultures are a severe biohazard
79
Histoplasmosis treatment
long-term treatment (4-6 months min) with azoles. Amphotericin in combination with oral azole for severe cases.

Bacteriology (8 decks)

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