Fungal Pathogens

Front 1

why dont superficial mycoses not elicit a host cellular response

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they grow in tissues that are not living

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cutaneous mycoses infect deeper in the epidermis and hair and nails what do they have that allows for growth

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keratinases that allow them to use keratin as a substance for growth

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tinea nigra and tinea versicolor are infections of what layer of skin

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the keratinized layer of skin

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clinical manifestations of cutaneous mycoses

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"ring worm" or tinea

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a chronic infection characterized by nodular and ulcerative lesions athat develop along the lymphatic glands that drain the primary site of inoculation

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lymphocutaneous sporotrichosis

a subcutaneous infection caused by sporothrix shenkii

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development of warty nodules that appear at sites of implantation of fungal elements

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chromoblastomycosis

a subcutaneous infection caused by dematiaceous fungi (fungi with brown to black melanin)

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lipophilic and grows in sweat glands

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Malassezia furfur

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(
tinea nigra is caued by melanin-producing dimorphic fungus called

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cladosporium (exophiala) werneckii

this is a superficial infection

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malassezia furfur and cladosporium wernickii are acquired from

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soil, animals, or other people by direct contact

they are superficial pathogens.

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cutaneous infections are caused by what kind of fungi

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dermatophytes

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three genera of dermatophytes

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microsporum
trichophyton
epidermophyton

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three classifications of dermatophytes

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geophilic (from soil)
zoophilic (animals)
antrophilic (humans)

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causes sporotichosis and is found in decaying vegetation
is dimorphic
grows as budding yeast at 37' and hypahae at 24'

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sporothrix shenkii

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causes chromoblastomycosis

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dematiaceous fungi (fungi with brown and black melanin)

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diagnosis of superficial and cutanteous myscoses depends on

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observing fungal elements in clinical specimans and NAOH mount

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endothrix

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refers to fungal elements inside hair shaft

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ectothrix

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refers to infection around the hair shaft

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this group of drugs is helpful for treatment of dermatophytes along with griseofulvin

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azoles

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what might be required for subcutantous fungal infetions

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surgical interventsion

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the most important fungal pathogen of man in terms of frequency, the number of types of diseases, and severity

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C. albicans

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frequent cause of diaper rash and viginitis

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C. albicans

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fungi imperfecti (deurteromycetes means

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sexual forms are unknown

e.g C. albicans (although they mate via cell fusion)

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common inhabitant of mucous membranes and digestive tract of humans - not found to be free living

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c. albicans

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stains for C. albicans

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gram stain - unlike most fungi

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C. Albi grows in what form

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budding yeast of culture - forms creamy white east colonies

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C. albicans forms what beneath agar surface on rich media at neutral pH

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c. albicans
vegetative hyphae

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C. albi - form aerial hyphae?

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no

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chlamydospores forms what forms at the ends of hyphae under nutrient limiting conditions in what fungi

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c. albicans

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what kind of form of C. albicans is predominate in tissue invasion

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hyphae and pseudohyphae

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what kind of epithelium does c. albicans invade

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stratified squamous lines oral cavity, tongue, esophagus, and vagina

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oropharyngeal candidiases is inflammation of

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mucosa or mucositis -
affects 40% of pts receiving chemotherapy. often causes pain.

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thrush =

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acute pseudomembranous candidiases

white patches on mucosa

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erythematous candidiases

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mild, reddening of mucosa

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flattening of tongue papilli happens in what kind of infection

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c. albicans

central papilary atrophy of dorsal tongue

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invasion of epithelium at corners of mouth where upper and lower lips meet - caused by C. albicans

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angular cheilitis

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what is the primary defense against C. albicans

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epidermis and epithelial lining of mucosal surfaces

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secretions in saliva that work against c. albicans

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histatin in saliva and definsins in epithelium

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intradermal injection with C. albicans and a positive DTH would indicate

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host has normal cell mediated immune response because c. albicans is part of the normal flora - lack of DTH and you know you are dealing with a compromised pt

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Ab against C. albicans

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present but not associated with protection

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abundantly expressed on true hyphae an not yeast which mimics mammalian epithelial cell proteins and allows C. albicans to become crosslinked to mucosal surfaces w/ host enzyme

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Hyphal Wall Protein (Hwp1

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cross linking enzyme that links host and C. albicans

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transglutaminase

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permits attachement of C. albicans to mucosal epithelial cells and to host proteins such as fibronectin

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adhesions from laarge agglutinin like sequences gene family (ALS)

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secreted aspartyl proteinases (SAPs)

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hydrolytic enzymes, along with phosphatases allow c. albicans to degrade host proteins

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important mechanism of azole drug resistance

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efflux pumps

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the source of c. albicans is usually

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from the host themselves (although can be spred orally and sexually)

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laboratory evaluation and identification of C. albicns
(2 - presumptive vs. definitive)

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presumptive: germbe tube formation in serum w/in 1-2 hours
Definitive: fermenatation and assimilation of carbohydrate and other compounds

note: variable germ tubes can help distinguish isolates

Front 47

azoles work how

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inhibit enzymes involved in erogosterol synthesis.

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why not use azoles prophylactically

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drug resistance

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used for severe candida infections - binds ergosterol

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Amphotericin B - cidal!

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two common resistance mechanisms for anti-fungals

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mutation of target enzyme and increased expression of efflux pump

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found in pts with HIV - differing in repetitive DNA from C.albicans

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C. dubliniensis

forms germ tubes but less frequently than C. albicans

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two organisms that account for approxiamately 70-80% of yeast isolated from patiets with invasive candidiases

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C. glabrata and C. albicans

Glabrata has recently become important because its increase incidence - less suseptible to azoles and Amphotericin B

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recently has become important because of its increasing incidence worlwide and intrinsically less suscepttible to azoles and Amphotericin B then C. albicans

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C. glabrata

Front 54

how do macrophages contribute to the response by host to a primary fungal infection

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macrophages become activated and "wall off" fungi

can be latent for years with no symptoms - then reactivated when host is immunosuppressed

Front 55

histoplasma capsulatum displays what kind of typical fungal growth

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dimorphic, growing in hyphal form in enviroment and yeast form in infected tissue

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mycelial

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hyphal

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hyphal characteristics of histoplasma capsulatum

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septate branching hyphae that bear spores called microconidia. macroconidia are called tuberculate

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tuberculate

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macroconidia of histoplasma have a characteristic morphology and are called

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yeast form of histoplasma capsulatum yeast form is found w/in what kind of cell

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macrophages (some in epithelial cells)

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an inportant attribute for virulence for H. capsulatum

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can grow in macrophages - surviving phagocytic vacuole

migrates to mediastinal lymph node, spleen, liver

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once histoplasma capsulatum has replicated w/in marocphages - it gets transfered via migration to

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to lymph nodes, sleen, liver
yeast prliferate for 9-15days
onset of host cell-mediated immunity
(sometimes found in epithelial cells)
mostly intracellular infection unless there is an overwhelming histoplasmosis

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acute versus chronic pulmonary histoplasmosis would be seen in what individuals

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acute in immunocompetent

chronic in immunosuppressed

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chronic pulmonary histoplasmosis is often mistaken for

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TB -

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native habitat and mode of transmission for histo. capsulatum

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soil is habitat and transmission is not person to person

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a positive histoplasm skin test indicates

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exposure to organisma and not necessarily active infection

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for disseminated histoplasmosis what test will always be positive

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Wright stain of peripheral blood showing intracellular yeasts w/in macorphages - organism can also be isolated from blood cultures

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for chronic pulmonary histoplasmosis, what may aid in diagnosis

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chest X-ray, CF test, sputum cultures, and possibly wright test of sputum
histoplasma uses wright stain

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common infection fo dogs, mainly sporadic infections in immunocompetant (primary pathogen) many cases in immunocompromised

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Blastomycosis (bastomyces dermatitidis

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Blastomyces dermatitidis - hyphal growth?

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hyphal growth with aerial spores

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growth of b. dermatitidis in culture

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cultures appear cottony - at 37' - grow as yeast with single buds having characterisitic broad base

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smooth or rough colonies (b. dermatitidis)

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smooth

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pathogenesis of B. dermatitidis

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1. B dermatitidis dwells as saprophyte - human inhales spore from soil
2. acute primary pulmonary infection may be asymptomatic
3. may resolve or progress i lungs or other organs (trophism for skin and bones)

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B. dermatitidis is tropic for what organs

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skin and bone

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Bad1

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(Blastomyces adhesin 1)
surface protein on B. dermatidtidis required for virulence by promoting the uptake by macrophages

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Bad1 has homology to invasin genes of gram negative bacteria and promotoes uptake by

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gram negative

macrophages

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pathogenesis of histoplasma capsulatum

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inhaled spores (microconidia)
reach small bronchioles or alveoli
germinat 2-3 days
yeasts proliferate w/in macro
macropha migrate to lymph nodes, sleen, liver
yeast prliferate for 9-15days
onset of host cell-mediated immunity
(sometimes found in epithelial cells)
mostly intracellular infection unless there is an overwhelming histoplasmosis

Front 77

acute pulmonary histoplasmosis and disseminated histoplasmosis caused by histoplasma capsulatum would be seen in what individuals

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acute seen in immunocompetant and chronic in immunocompromised

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chronic pulmonary histoplasmosis is often mistaken for

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TB -

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native habitat and mode of transmission for histo. capsulatum

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soil is habitat and transmission is not person to person

Front 80

a positive histoplasm skin test indicates

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exposure to organisma and not necessarily active infection

Front 81

for disseminated histoplasmosis what test will always be positive

Back 81

Wright stain of peripheral blood showing intracellular yeasts w/in macorphages - organism can also be isolated from blood cultures

Front 82

for chronic pulmonary histoplasmosis, what may aid in diagnosis

Back 82

chest X-ray, CF test, sputum cultures, and possibly wright test of sputum

Front 83

common infection fo dogs in endemic zones and canine infection are often sever or lethal

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Blastomycosis (bastomyces dermatitidis

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structure of b. dermatitidis

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dimorphic
filamentous haypa forms w/ associated aerial spres

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growth of b. dermatitidis

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enviroment (and culture): hyphi w/ aerial spores
37 degrees: yeast - single buds, broad base

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smooth or rough colonies (b. dermatitidis)

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smooth

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pathogenesis of B. dermatitidis

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1. B dermatitidis dwells as saprophyte - human inhales spore from soil
2. acute primary pulmonary infection may be asymptomatic
3. may resolve or progress i lungs or other organs (trophism for skin and bone)

Front 88

B. dermatitidis is tropic for what organs

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skin and bone

Front 89

Bad1

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surface protein on B. dermatidtidis required for virulence and promotes the uptake of fungi by macrophages

Front 90

Bad1 has homology to invasin genes gram Gram what bacteria
and promotoes uptake by

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gram negative

macrophages

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B dermatidis is antigenically cross reactive with

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H. capsulatum

Front 92

B. dermitidis grows exclusively in what form in host

may be detected w/

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yeast

KOH mounts or fungal stains in infected area

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immunodiffusion test for detection of what is used for detecting B. dermatitidus

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immunodiffusion test for patient antibodies to "A" antigen produced fro cultures filtrates of B. dermatidis

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40% of infected individuals have symptoms consistant w/ lower respiratory infection and/or systemic illness w/ cough, sputum production, chest pain, malaise, fever, chills, night seats, anorexia, weakness, arthralgia

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Coccidioides immitis

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how long does the disease caused by coccidioides immitis last

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2-6 days

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valley fever caused by

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coccidioides immitis
a small number of cases progress to a chronic pulmonary form characterized by cavity formation

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barrel-shaped arthroconidia which are easily fragmented and highly infectious

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Coccidioides immitis

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spherules are form in host, rupture leads to large numbers of endospores in tissue which develop into spherules

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Coccidiodides immitis

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how does one become infected with coccidioides immitis

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inhaled

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initial response to coccidioides immitis consists of what cells

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macrophages and neutrophils

but fungi are resistant to killing by neutrophils

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symtoms are more common in dark skin men

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coccidioides immitis

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wagon whell appearance of yeasts found in tissues

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paracocidioides brasilliensis

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yeast has single bud coming off yeast w/ broad base

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blastomyces dermatitidis

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Wright stain helps with the diagnosis of

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Histoplasmosis