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129 Cards in this Set
- Front
- Back
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what are the two groups of fungi?
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2 and 3: fungi can be divided into two categories: true and opportunistic
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what are cutaneous infective agents also called.
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cutaneous infective agents aka dermatophytes
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what do dermatophytes infect?
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dermatophytes affect skin and keratin
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what do you know about the morphology of all systemic infective agents?
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systemic infective agents are all dimorphic
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when do opportunistic agents cause a problem?
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burn, trauma, or immunosuppression only then do they cause problem
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where do fungi grow in general?
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Saprophytic organisms (grow on organic matter)
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how are fungi divided
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Divided by site of infection: cutaneous, subcutaneous, systemic (true pathogens vs opportunistic pathogens), agents of allergy
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which fungi are agents of allergy
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agents of allergy mainly refer to allergic responses to aspergillosis-causing fungi (most common is aspergillosa fumigatus)
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what special thing is the fungal cell membrane composed of?
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Cell membrane composed of ergosterols which are targets of antifungal agents. human cells have cholesterol
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what is the fungal cell wall made up of?
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Cell wall composed of the polysaccharide chitin (a polymer of N-acetylglucosamine) and other polysaccharides polymers composed of mannose and glucose which are called mannans and glucans)
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what are glucans and mannans?
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a glucan is a polymer of glucose. a mannan is a polymer of mannose.
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why are the sugars on the cell wall of fungi important?
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they are antigens that can be markers for fungi in laboratory tests and important drug targets
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where is ergosterol in fungi?
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ergosterol is inside the cell wall on the plasma membrane which is itself also inside the cell wall
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what are some common fungal medicines and how do they work?
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Amphotericin B and nystatin bind to ergosterol forming pores that disrupt membrane function resulting in cell death
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what are some ways that antifungals cell work on fungi
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membrane disruption, mess with microtubule function, mess with nucleic acid synthesis, mess with ergosterol synthesis, mess with glucan synthesis
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what do fungi require for growth?
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Fungi are heterotrophs so they require preformed organic carbon for growth
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how do fungi get nutrients from their environment?
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they secrete degradative enzymes to obtain soluble nutrients from their environment
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where do most fungi reside?
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Most fungi live in soil. However the Candida species are part of normal mucosal flora
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what are the 2 major forms of fungi?
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yeast and mold forms
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describe yeasts
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single cell - reproduce by budding, rigid cell wall
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describe molds
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aka filamentous fungi. molds are made up of branching filaments (ie hyphae). these hyphae produce spore heads. when a mass of branching hyphae grow together in a mat of growth the mass is called a mycelium aka mold.
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what are the two types of hyphae
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septate and nonseptate. each septation has its own nucleus
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what are some species of fungi? (heat?)
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Some species are dimorphic (thermally regulated) yeasts – in body tissue, body temperatures; molds – in culture, ambient temp
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what is weird about Candida and dimorphism?
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some of the candida species are dimorphic but aren't thermally dimorphic
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what is the main way that filamentous fungi reproduce?
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Sporulation is the principal means by which filamentous fungi aka molds reproduce
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describe the qualities of the spores molds produce
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They are metabolically dormant, can be transmitted by air or water to new sites where they become metabolically active and germinate and establish colonies. They are produced sexually or asexually. They are not like bacterial spores that are highly resistant to heat, UV, and disinfectants. In fact they are very fragile
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what is one agar used to culture fungi?
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saboraud dextrose agar. the low pH of this agar inhibits the growth of bacteria. fungi agar can also contain antibiotics to inhibit bacterial growth
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what is another way to ID fungi isn't looking for the appearance of colonies on agar?
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you can do examine patient tissue samples (direct smears) via microscopy or you can conduct serological testing for Ab and Ag.
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bronchoalveolar lavage
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a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then recollected for examination
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what are cutaneous mycoses also called and what are the species that make up the group?
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also called dermatophytes, trichophyton, epidermophyton, microsporum
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where do cutaneous mycoses cause infection?
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they are non-invasive fungi that cause superficial infections of hair, skin and nails.
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how are the cutaneous mycoses divided epidemiologically?
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Divided by natural habitat. Anthropophilic (residing on human skin), zoophilic (residing on animals), geophilic (residing in the soil)
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how are cutaneous mycoses transmitted?
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Transmission by contact with infected skin or hair. usually transmitted from person to person. sometimes transmitted animal to human
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what do dermatophytes use for nutrition and are they invasive?
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Dermatophytes use keratin as a source of nutrition, they do not invade underlying nonkeratinized tissue
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what disease do cutaneous mycoses cause?
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dermatophytes (trichophyton, epidermophyton, microsporum) cause the tinea diseases
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tinea capitis aka
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scalp ringworm
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tinea cruris aka
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jockitch
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tinea unguium aka
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fungal nail infection aka onychomycosis
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how do you treat the tineas? what are they caused by?
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Oral or topical therapy. nail infections require oral therapy for months. they are caused by the dermatophytes: trichophyton, epidermophyton, microsporum
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define mycose
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any disease caused by a fungus
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what are subcutaneous mycoses?
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Fungal infections of the dermis, subcutaneous tissue, and bone. examples of the diseases these cause include the sporotrichosis, chromoblastomycosis, and mycetoma diseases
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where do you get subcutaneous mycoses from?
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Causative agents reside in soil and decaying or live vegetation, usually acquired through traumatic lacerations or puncture wounds, more common if frequent contact with soil and vegetation and wear little protective clothing
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what kingdom are fungi in
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mycota
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what is sporotrichosis caused by?
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Sporothrix schenckii
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what is sporotrichosis
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Granulomatous lesions at the puncture site, secondary lesions along draining lymphatics may be seen. the disease can be self-limiting or chronic
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who is at risk for sporotrichosis?
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common in the US, higher risk is third world countries. farmers and people who spend a lot of time outside
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Sporothrix schenckii morphology
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dimorphic: yeast form that buds in infected tissue; mycelial (filamentous) form in culture which is at lower temperature compared to tissue
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what is chromoblastomycosis?
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Following a puncture wound, a small violet wart-like lesion develops. With time, clusters of these skin lesions can develop along the lymphatics. these clusters develop into crusty abscesses. the violet color can be described as dematiaceous (dark brown pigmented colony infection)
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where do you see chromomycosis?
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not seen in this US that much; usually seen in tropical and subtropical regions
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how do you treat chromomycosis?
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surgery and antifungals
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what is a mycetoma
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localized abscess that usually develops on the feet that discharges pus, serum and blood through sinuses of their own creation the organisms can spread to bones causing crippling deformities. their defining characteristic is the presence of colored grains (black, white, red, or yellow) composed of compacted hyphae in the exudate
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what causes mycetoma
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actinomycetes fungi and various other soil fungi
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how do you treat mycetoma?
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surgical excision
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do we see mycetoma in the US?
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may seem this in this country
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how do the sinuses of mycetoma get created?
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orgs by their growth make their own channels
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where do you acquire the organisms that cause mycetoma
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usually found in the soil. actinomycetes fungi and various other soil fungi cause mycetoma
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what is the defining characteristic of mycetoma disease?
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definition of mycetoma is the presence of colored grains composed of compacted hyphae in the exudate
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who do true pathogens and opportunistic pathogens invade?
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infect healthy people vs infect debilitated people
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how are the true pathogens and opportunistic pathogens that affect people different?
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true pathogens are dimorphic
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what are the SYSTEMIC opportunistic fungi pathogens diseases?
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candidiasis, cryptococcosis, aspergillosis, mucormycocis, pneumoncystis jurovecii
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what are the true pathogenic diseases that are systemic
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coccidiodomycosis, histoplasmosis, blastomycosis, paracoccidiomycosis. these are all dimorphic fungi.
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how do the dimorphic systemic fungi infect you?
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Entry into host by inhalation of airborne spores. these spores germinate in lung
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what are the diseases caused by dimorphic systemic fungi?
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Asymptomatic primary pulmonary infection is common, acute pulmonary disease less common, chronic pulmonary or disseminated infection is rare
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what causes coccidiomycosis
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coccidiodes immitis
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where does coccidiomycosis occur
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Most cases occur in the arid areas of SW USA, central and SA
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where do c. immitis come from
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In the soil, these fungi produces hyphae that break down into arthrospores (form arthrospores by septation of fungal filaments); these arthrospores are then inhaled by humans
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if c. immitis is not treated what can happen?
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it can disseminate to bones and CNS, causing disease. but most of the time c. immitis remains asymptomatic
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how does c. immitis cause disease in tissue?
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in tissue cells it causes a big spherule with these endospores that can break out of the spherule.
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how do you diagnose c. immitis
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you diagnose it by culture, histopathology (e.g. get lung biopsy), and serology (antibody and antigen)
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any special considerations for culturing c. immitis
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you can culture it to diagnosis it but it's dangerous to do so because it can easily get airborne and can cause lab infections
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what causes histoplasmosis
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histoplasma capsulatum
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where do you find histoplasma capsulatum?
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Occurs worldwide but most prevalent in central North America, particularly Ohio and Mississippi River valleys
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what is the reservoir of histoplasma capsulatum?
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these fungi are found in soil with a high nitrogen content such as soil found in areas contaminated by bat or bird droppings. these organisms produce conidia that are inhaled in lungs and germinate into yeast-like cells (because of body temperature)
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what is the hallmark of histoplasmosis?
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Hallmark of histoplasmosis caused by histoplasma capsulatum is infection of lymph nodes, spleen, bone marrow and other parts of the RES with intracellular growth in macrophages
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what types of infections can comprise histoplasmosis
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Infection can be asymptomatic (usually), acute, chronic, or disseminated
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who gets disseminated histoplasmosis the most and what organs does it affect
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Disseminated disease occurs higher in the immunocompromised and children (cause kids typically don't have a mature immune system), disseminated disease can occur in many different organs and sites e.g. bone marrow, skin, CNS, adrenals, liver, lymph nodes
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what stains do you use to diagnose histoplasmosis via microscopy and what do you look for when you do so?
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calcofluor white and Giemsa stain (GMS): calcofluor: look for small (tiny) pumpkin seed shaped cells. giemsa: see a whole bunch of yeast in the macrophages (histoplasma capsulatum can survive intracellularly inside macrophages)
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what tissue samples do you culture to determine histoplasmosis?
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blood, B.M., and any other tissue that h. capsulatum may have disseminated to.
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what is another way to diagnosis histoplasmosis besides microscopy
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Antigen detection in blood, urine, Bronchoalveolar Lavage (BAL) as well as antibody detection
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what causes blastomycosis
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Caused by Blastomyces dermatitidis
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where is the reservoir for blastomyces dermatitidis and how do you get it in your body?
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the organism is found in soil where it releases conidia which you inhale into your lungs. inside the lungs it germinates into thick walled yeast cells
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what diseases does blastomyces dermatitidis cause?
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1. Asymptomatic pulmonary infection (usually) 2. Symptomatic infection: pulmonary or disseminated 3. Disseminated: skin, bones, organs, CNS
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in which geographical areas do you find blastomyces dermatitidis?
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in the southeastern and southcentral US. especially in states bordering the Ohio and Mississippi River valleys and in states bordering the Great Lakes (saint louis is endemic for blastomyces dermatitidis!)
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what does blastomyces dermatitidis look like on a microscope slide?
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you see a broad base bud that's very large that's thick walled. you don't see pinching between the buds
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besides using a microscope how else can we diagnose blastomycosis?
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1. Culture of sputum, BAL, lung biopsy, other tissue 2. Serology and antigen detection not sensitive or specific
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what causes paracoccidiodomycosis, aka, and geographical location
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paracoccidiodes brasilensis, South American blastomycosis, major endemic dimorphic fungus in Latin America
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what are the symptoms of paracoccidiodomycosis? who does it cause disease the most in?
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Clinical presentation similar to histo and blasto EXCEPT most common secondary site of infection (ie disseminated) is the mucosa of the mouth and nose where destructive lesions may develop. 90% of symptomatic disease occurs in males; female hormones may be inhibitory
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how do diagnose paracoccidiodomycosis under a microscope?
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at 37 degrees celsius, it looks like pilot or mariner’s wheel (one circle surrounded by other circles that are attached to it)
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how else do you diagnose paracoccidiodomycosis besides microscopy
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Culture: sputum, BAL, tissues, scrapings; Serologic testing
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what are the most common opportunistic mycoses
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OPPORTUNISTIC MYCOSES are Candidiasis, Cryptococcocis, Aspergillosis, Mucormycosis, Pneumocystis; rarely cause disease in healthy individuals
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what is the morphology of mucormycosis disease causing fungi
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mucormycosis are broad, nonseptated, branching hyphae
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what is the most common species that causes candidiasis
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Candida albicans is the most common species
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where is the reservoir for candida albicans, morphology, and reproduction
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Normal flora of skin, mucous membranes, GI tract, GU tract. you should never find it in the blood! budding yeast and hyphal forms. it reproduces by budding
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what are the 2 types of disease candidiasis causes?
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mucocutaneous and systemic
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what are the mucocutaneous candidiasises manifestations?
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thrush (oral candidiasis), vulvovaginitis, esophagitis (candidiasis doesn't infect esophagus in immunocompetent), diaper rash
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describe oral thrush
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patches of creamy white exudate with a reddish base cover the mucous membranes of the mouth
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describe vulvovaginitis
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vaginal itching and thick copious secretions wetting the underwear (see patches of cottage cheese-appearing white clumps affixed to the vaginal wall)
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who does systemic candidiasis usually occur in and where does it occur in?
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Systemic candidiasis occurs in immunosuppressed, cancer patients, patients on antibiotic therapy. it can involve the GI tract, kidneys, liver, spleen, bloodstream, urinary tract, respiratory tract, heart, and eye. it can cause diseases like endocarditis, retinitis, and ophthalmitis
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how do you diagnosis candidiasis
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culture is the mainstay of diagnosis. it is very easy to culture
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describe candida albicans morphology
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it is dimorphic. it can do be both budding yeast and hyphae at any temperature. temp doesn't affect what form it is
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what is cryptococcocis caused by
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Caused by the yeast Cryptococcus neoformans
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morphology of cryptococcus neoformans
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this organism has a thick capsule which can be observed by India ink stain
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where is cryptococcocis foud?
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Found worldwide, particularly in soil containing bird droppings, especially pigeon droppings
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what are the clinical manifestation of cryptococcocis neoformans?
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the most common clinical manifestation is a mild lung infection. in immunocompromised patients cryptococcus neoformans can disseminate to the brain and meninges. meningitis can also occur in immunocompetent patients
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where do you usually see meningeal crytococcocis?
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usually see these it in those who aren't diagnosed with HIV or who arent taking HIV drugs. these people present with headaches, and nonsensical mental status
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what does a gram stain of cryptococcosis neoformans look like
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circles that link together like beads on a chain that have a thick capsule. thick capsule is the key theme to how it looks on all slide preparations
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what causes aspergillosis, reservoir for these organisms
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It is caused by several species of the filamentous fungus, Asperigullus. However, the most common species is Aspergillus fumigates. it is found in soil, dust, and decomposing organic matter. generally though its found everywhere! (e.g. lecture hall carpet)
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what are the three types of dieases of aspergillosis?
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1. superficial or colonizing syndromes 2. invasive. 3. allergy related manifestations
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superficial or colonizing syndromes of aspergillosis are...
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Otomycosis (ear infection where you see a mat of fungus in the ear), Onchomycosis, and Keratitis (cornea infection)
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describe the invasive types of aspergillosis disease
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invasive pulmonary aspergillosis and disseminated disease
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describe invasive pulmonary aspergillosis
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Invasive pulmonary aspergillosis is caused by spores getting into the lungs. when this happens you can manifest with hemoptysis because the fungus is able to angioinvade the endothelium.
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describe invasive disseminated aspergillosis
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Disseminated disease often progresses from invasive pulmonary aspergillosis. the organism is able to disseminate via contiguous spread or hematogenously [it can do this because it is angioinvasive]. disseminated invasive aspergillosis has a very high mortality rate.
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what does invasive aspergillosis have to do with cancer?
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angioinvasiveness. this can be an end stage disease in hematology oncology patients (immunosuppressed).
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what are the two allergy related manifestations of aspergillosis
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1. allergic disease 2. allergic bronchopulmonary aspergillosis
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describe the allergic disease caused by aspergillosis
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a condition caused by an aberrant host immune response to noninvasive aspergillus infection. this is an allergy so it is mediated by high levels of IgE. the disease occurs in immunocompetent patients. consistently high eosinophilia may lead to pulmonary fibrosis. Chronic sinusitis, which manifests itself as a nasal obstruction, headache, nasal polyps, may also occur. these allergies make these people miserable their entire lives.
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describe allergic bronchopulmonary aspergillosis
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this is a long-term allergic response to Aspergillus. it results from an abnormally high IgE mediated immune response to Aspergillus hyphae colonizing your airways. The condition may progress to bronchiectasis (dilation of the bronchioles so you can't breathe) and permanent lung damage (pulmonary fibrosis). major finding: pulmonary infiltrates due to atelectasis
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what is atelectasis
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Atelectasis is defined as the lack of gas exchange within alveoli, due to alveolar collapse or fluid consolidation. It may affect part or all of one lung. It results in peripheral blood eosinophilia (an increase in peripheral bloood eosinophils) and elevated IgE and IgG against Aspergillus species. It is a condition where the alveoli are deflated which is distinct from pulmonary consolidation.
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what is an aspergilloma
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it is a fungal ball composed of a mass of hyphae growing in a preexisting pulmonary cavity or sinus cavity. You must remove it surgically if at all possible. If it isn't removed, an aspergilloma can result in death. However, the condition can also be asymptomatic.
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how do you diagnose aspergillus
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you diagnose aspergillosis thru microscopy of tissue samples, culturing, and serology. diagnosis is very difficult because of the condition tends to cause a lot of false negatives. consequently if you suspect someone may have it you should do presumptive treatment before it is officially diagnosed
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what does microscopy reveal for aspergillus
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chains of septated hyphae with dichotomous (goes different directions) branches at 45 degree angles. you'll also see granulomas in tissue
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what does serology look for in aspergillosis
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serology attempts to detect the presence of the aspergillus galactomannan antigen in the serum.
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what causes mucormycosis
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it is a disease caused by the Zygomycetes group of filamentous fungi. these are NON-SEPTATED FUNGI. Rhizopus is the most common genus of this group.
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where do you find the organisms that cause mucormycosis and who gets infected by them the most?
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Organisms ubiquitous in nature; Infections almost entirely restricted to those with underlying predisposing condition: diabetes, burns, immunosuppression
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describe mucormycosis
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Rhinocerebral mucormycosis is a disease that begins in the nasal mucosa or sinuses and progresses to the orbits, palate and brain. The condition is very aggressive (organism grows very very fast) and so it rapidly fatal. To treat it surgical debridement must be performed along with antifungal medicine. It causes a black nasal discharge!
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how do you diagnose mucormycosis
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you detect large non-septated hyphae in tissue slides and by culturing it (it fills up the entire agar plate very quickly with a wooly colony; it is a lid lifter)
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what does pneumocystis jurovecii cause, aka.
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formerly known as P. carinii. causes pneumonia in immunosuppressed individuals, particularly those with AIDS. Hypoxia is a hallmark of PCP pneumonia (ie very low pO2)
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where do you find the pneumocystis jurovecii organism and how is it transmitted to humans
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organism is ubiquitous in nature and it is transmitted viaairborne transmission
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can you reactivate a latent infection of pneumocystis jurovecii?
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no this is no longer held as mode of transmission. de novo infection is how you get it
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diagnosis of pneumocystis jurovecii
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you diagnosis it by direct microscopy. this organism cannot be cultured in vitro
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