Fungal infections

geographical predilection of black piedra

Reported from tropical areas in Latin America and Central Africa.

Black piedra clinical syndromes

-Small dark nodules surrounding the hair shafts.
-Asymptomatic and generally involves the scalp.

What is one common cutaneous mycoses

Dermatophytosis

Dermatophytosis

complex of diseases caused by several species of filamentous fungi in the genera Trichophyton, Epidermophyton, and Microsporum, collectively known as the dermatophytes

All dermatophytes possess the ability to what?

cause disease in humans and/ or animals

What has the ability to invade the skin, hair, or nails?

dermatophytes

T/F dermatophytes are
Keratinophilic

true

Keratinophilic and keratinolytic:

able to break down the keratin surfaces of hair and skin.

In skin infections dermatophytes invade only what layer/s of the skin

the stratum corneum.
-Penetration below the granular layer of the epidermis is rare.

The different forms of dermatophytosis are referred to as what?

tineas or "ringworm.

tinea capitis affects what?

the scalp, eyebrows, and eyelashes
-The capita, or head

tinea barbae affects what?

the beard

tinea corporis affects what?

the smooth or glabrous skin

tinea cruris affects what?

the groin

tinea pedis affects what?

the foot

tinea unguium affects what?

the nails (also known as onychomycosis).

geographic predilections of dermophytes

Worldwide distribution.

dermophyte transmission

-Direct transmission from infected host to susceptible individual.
-Fomites

Who is at risk of getting a type of dermophyte

-No sex, age, or race predilection
-Individuals of both sexes and all ages are susceptible to dermatophytosis.
-Tinea capitis is more common in prepubescent children, and tinea cruris and tinea pedis are primarily diseases of adult males.
-T. tonsurans is

Infections by _____________________ are generally endemic but may assume epidemic proportions in selected settings (e.g., tinea capitis in schoolchildren).

dermatophytes

Dermatophytosis:

classic "ringworm" pattern of a ring of inflammatory scaling with diminution of inflammation toward the center of the lesion.

Tineas of hair-bearing areas:

often raised circular or ring-shaped patches of alopecia with erythema and scaling or as more diffusely scattered papules, pustules, vesicles, and kerions (severe inflammation involving the hair shaft).

Infections of smooth skin:

Commonly erythematous and scaling patches that expand in a centripetal pattern with central clearing.

Dermatophytoses of the foot and hand may often become complicated by _____________; the nail plate is invaded and destroyed by the fungus.

onychomycosis

Onychomycosis (tinea unguium) is caused by what?

different dermatophytes and affects approximately 3% of the population in tropical countries.

What is onychomycosis

It is a disease seen mostly in adults, with toenails affected more commonly than fingernails.

onychomycosis is usually (acute/chronic)

The infection is usually chronic with the nails becoming thickened, discolored, raised, friable, and deformed.

what is the most common etiologic agent for onycomycosis in most countries.

T. rubrum

A rapidly progressive form of onychomycosis that originates from the proximal nailfold and involves the upper and underside of the nail is seen in __________ patients.

AIDS

Laboratory diagnosis of dermatophytes

-Relies on the demonstration of fungal hyphae by direct microscopy of skin, hair, or nail samples and the isolation of organisms in culture.
-Specimens are mounted in a drop of 10% to 20% KOH on a glass slide and examined microscopically. Filamentous hyal

dermatophyte cultures

-Useful and can be obtained by scraping the affected areas and placing the skin, hair, or nail clippings onto standard mycologic media such as Sabouraud agar, with and without antibiotics, or dermatophyte test medium. Colonies develop within 7 to 28 days.

Major distribution of endemic mycoses

Are most dimorphic fungal pathogens considered primary systemic pathogens?

yes
infect both "normal" and immunocompromised hosts and have propensity to involve the deep viscera after dissemination from the lungs.

Endemic mycosis caused by either of two indistinguishable species:

Coccidioides immitis and C. posadasii.

Coccidioidomycosis is caused by inhalation of what?

infectious arthroconidia.

How does Coccidioidomycosis affect people

May range from asymptomatic infection (in most people) to progressive infection and death.

Coccidioidomycosis
Epidemiology

-Endemic to the southwestern United States, northern Mexico, and scattered areas of Central and South America.
-C. immitis is found in soil.
-Growth of fungus in the environment enhanced by bat and rodent droppings.
-Exposure is higher in late summer and

Coccidioidomycosis
transmission

-Principally by inhalation of arthroconidia.
-Affect disproportionately persons aged 65 and older and those with human immunodeficiency virus (HIV) infection (? 20 per 100,000).

WHat is probably the most virulent of all human mycotic pathogens.

C. immitis

What happens after inhalation of only a few arthroconidia:

primary coccidioidomycosis including asymptomatic pulmonary disease (? 60% of patients) or a self-limited flulike illness marked by fever, cough, chest pain, and weight loss.

Allergic reactions by immune complex formation in 10% patients with primary coccidioidomycosis:

Erythematous macular rash.
Erythema multiforme.
Erythema nodosum.

Primary disease of Coccidioidomycosis

frequent spontaneous resolution, confers strong, specific immunity to reinfection (detected by the coccidioidin skin test).

Extrapulmonary sites of infection for Coccidioidomycosis:

skin, soft tissues, bones, joints, and meninges.

Mortality in disseminated disease (coccidiodiomycosis):

more than 90% without treatment.

Progression to secondary coccidioidomycosis in patients with symptoms for 6 weeks or more:

-Nodules
-Cavitary disease.
-Progressive pulmonary
disease (5% of cases)
-Single or multisystem
dissemination (1% of this
population).
--Results in fatality usually.
--More common in
immunocompromised people

Is chronicity common in Coccidioidomycosis?

yes!!!

At risk groups for coccidioidomycosis:

Males (9 : 1), women in the third trimester of pregnancy, individuals with a cellular immunodeficiency (e.g., AIDS, organ transplantation recipients, those treated with tumor necrosis factor antagonists), and persons at the extremes of age are at high ris

What causes histoplasmosis?

two varieties of Histoplasma capsulatum:
-H. capsulatum var. capsulatum
-H. capsulatum var. duboisii.

What is the cause of pulmonary and disseminated infections in the eastern half of the United States and most of Latin America.

H. capsulatum var. capsulatum

Laboratory diagnosis of Coccidioidomycosis

-Histopathologic examination
-Isolation of the fungi inculture.
-Serologic testing.
-Direct microscopy
-Tissue from biopsy: stained with H& E or specific fungal stains GMS or PAS.
-Culture: on routine mycologic media at 25 � C.
-Serologic procedures for i

What causes predominantly skin and bone lesions. Restricted to the tropical areas of Africa.

H. capsulatum var. duboisii:

Histoplasmosis capsulati: geographic predilection

regions of the Ohio and Mississippi river valleys in the United States, and Mexico and Central and South America.

Histoplasmosis duboisii (African histoplasmosis): geographic predilection

is confined to the tropical areas of Africa.

Outbreaks of histoplasmosis: associated with what?

exposure to bird roosts, caves, and decaying buildings or urban renewal projects involving excavation and demolition

Inhaling the infective elements
of histoplasmosis causes what?

the initial infection

What cause the initial infection of histoplasmosis

Inhaling the infective elements

Basis of histoplasmosis outbreaks:

Aerosolization of microconidia and hyphal fragments in the disturbed soil with subsequent inhalation by exposed individuals.

Are most cases of histoplasmosis a/symptomatic?

asymptomatic

How can you tell if someone has histoplasmosis if they are asymptomatic?

only by skin testing

Reactivation of the disease and dissemination of histoplasmosis is common among?

immunosuppressed individuals, especially those with AIDS (not HIV but AIDS)!!.

Usual route of infection: Histoplasmosis Capsulati

inhalation of microconidia, then germinate into yeasts in the lung and may remain localized or disseminate hematogenously or by the lymphatic system.

Clinical presentation of Histoplasmosis Capsulati

depends upon the intensity of exposure and immunologic status of the host.

What determines whether someone is a/symptomatic when infected with histoplasmosis?

Exposure.
-Asymptomatic infection: 90% of individuals after a low-intensity exposure.
-Exposure to a heavy inoculum: most individuals exhibit symptoms.

Self-limited form of acute pulmonary histoplasmosis: (symptoms)

flulike illness with fever, chills, headache, cough, myalgias, and chest pain.

Most acute infections of histoplasmosis capulati resolve with what?

supportive care without specific antifungal treatment.

What can very heavy exposure of Histoplasmosis Capsulati lead to?

might lead to acute respiratory distress syndrome.

what is a rare complication of histoplasmosis?

Mediastinal fibrosis

progressive pulmonary histoplasmosis after acute infection can occur in

1 in 100,000 cases

Chronic pulmonary symptoms :

associated with apical cavities and fibrosis, more likely in patients with prior underlying pulmonary disease.

Chronic disseminated histoplasmosis:

-Weight loss and fatigue, with or without fever.
-Oral ulcers and hepatosplenomegaly are common.

Subacute disseminated histoplasmosis: fever, weight loss, and malaise.

-Oropharyngeal ulcers and hepatosplenomegaly are prominent.
-Bone marrow involvement may produce anemia, leukopenia, and thrombocytopenia.
-Other sites of involvement include the adrenals, cardiac valves, and CNS.
-Untreated, results in death in 2 to 24 m

Acute disseminated histoplasmosis is common in?

severely immunosuppressed individuals:
-AIDS.
-Organ transplant recipients
-Those receiving steroids or
other immunosuppressive
chemotherapy.
-Children younger than 1 year
and adults with debilitating
medical conditions are also at
risk.

Acute disseminated histoplasmosis May present with a septic shock:

Fever
Hypotension
Pulmonary infiltrates
Acute respiratory distress.

Acute disseminated histoplasmosis Other manifestations

Oral and gastrointestinal ulcerations
Bleeding
adrenal insufficiency
meningitis and endocarditis.

If untreated, acute disseminated histoplasmosis is fatal within

days to weeks!!!!

Laboratory diagnosis of histoplasmosis

-Direct microscopy.
-Culture of blood, bone marrow, or other clinical material (best in disseminated disease)
-Serology

The yeast phase of histoplasmosis can be detected where in the body

The yeast phase can be detected in sputum, bronchoalveolar lavage fluid, peripheral blood films, bone marrow, and tissue stained with Giemsa, GMS, or PAS stains.

Fungi are classified in a separate kingdom:

Kingdom Fungi.

What makes fungi cell different from other eukaryotes?

-Rigid cell wall of chitin and glucan
-cell membrane with ergosterol instead of cholesterol as the major sterol component.

T/f fungi have cholesterol in the cell membrane

False
ergosterol instead of cholesterol as the major sterol component.

are fungi uni or multi cellular?

May be unicellular or multicellular.

Bast on morphology fungi can be classified as?

molds or yeasts

What is one complication of antifungal medication?

Many antifungal drugs have hepatotoxicity because they are eukaryotes, its hard to find a drug that kills it without affecting us

how do yeasts reproduce?

reproduces by budding or fission.
A progenitor or "mother" cell pinches off a portion of itself to produce a progeny or "daughter" cell

how does yeast form pseudohyphae

Daughter" cells may elongate to form sausage-like pseudohyphae.

Yeast appearance

Usually unicellular and produce round, pasty, or mucoid colonies on agar.

are molds uni or multicellular?

multicellular

do yeasts or molds have hyphae

molds

how do hyphae elongate?

Hyphae elongate at their tips by apical extension.

Hyphae are either:

coenocytic (hollow and multinucleate) or septate (divided by partitions or crosswalls).

What is mycelium?

hyphae that form together to produce a mat like structure

What do mold colonies look like?

The colonies formed by molds are often described as filamentous, hairy, or woolly.

respiration for fungi

Most fungi: aerobic respiration
Some are facultatively anaerobic (fermentative)
-Ferment sugars
Some others are strictly anaerobic.
-Can switch to aerobic if O2 is present

are fungi heterotrophs or autotrophs

heterotrophs

describe the digestive system of fungi

-Does not have a digestive system!
-They secrete enzymes that digest outside the fungi, and fungi absorb the digested nutrients

biochemical versitilit of fungi

they produce primary and secondary metabolites

primary metabolites

e.g., citric acid, ethanol, glycerol

secondary metabolites

e.g., antibiotics [penicillin], amanitins, aflatoxins

is fungal growth faster or slower than bacteria?

slower

T/F Observation of colony is usually enough to identify the organism

true

fungal reproduction:

Sexual (involving meiosis, preceded by fusion of the protoplasm and nuclei of two compatible mating types)
or
Asexual (involving mitosis only).

Asexual spores consist of two general types:

sporangiospores and conidia.

Sporangiospores:

Asexual spores produced in a containing structure called sporangium

Conidia

Asexual spores borne naked on specialized structures (conidiophores) as seen in Aspergillus spp., Penicillium spp., and the dermatophytes.

Superficial Mycoses infections limited to what?

very superficial surfaces of the skin and hair.

how invasive are superficial mycoses?

-Normally asymptomatic
-Don't elicit an immune response
-Are nondestructive and of cosmetic importance.

Pityriasis versicolor:

characterized by discoloration or depigmentation and scaling of the skin.

Tinea nigra:

brown- or black-pigmented macular patches localized primarily to the palms.

Black and white piedra:

involve the hair, characterized by nodules composed of hyphae that encompass the hair shaft.

Cutaneous mycoses:

infections of the keratinized layer of skin, hair, and nails.

How invasive are cutaneous mycoses?

May elicit a host response and become symptomatic.
Illicits immune responce

Signs and symptoms of cutaneous mycoses

Signs and symptoms include itching, scaling, broken hairs, ringlike patches of the skin, and thickened discolored nails.

Infections of the skin involving cutaneous mycoses are called .

dermatophytoses

Subcutaneous mycoses:

deeper layers of the skin, including the cornea, muscle, and connective tissue.

How do Fungi gain access to deeper tissues?

by traumatic inoculation (broken skin) and remain localized, causing abscess formation, nonhealing ulcers, and draining sinus tracts.

What happens when subcutaneous fungi activate the immune system?

The host immune system recognizes the fungi, resulting in variable tissue destruction and frequently epitheliomatous hyperplasia.

does subcutaneous mycoses spread?

Tend to remain localized, rarely disseminate systemically.

Endemic Mycoses:

fungal infections caused by the classic dimorphic fungal pathogens

What is a dimorphic fungal pathogen?

fungi that can exist in the form of both mold and yeast depending on temperature

examples of dimorphic fungal pathogens

H. capsulatum, B. dermatitidis, E. pasteuriana, C. immitis, C. posadasii, P. brasiliensis, and T. (Penicillium) marneffei.

Thermal dimorphism

(exist as yeasts or spherules at 37 �C and molds at 25 �C)

Endemic mycoses geographic predilection

Generally confined to geographic regions where they occupy specific environmental or ecologic niches.

Endemic mycoses are also known as?

systemic mycoses

systemic mycoses:

true pathogens; can infect healthy individuals.

Endemic mycoses enter the body how?

via the respiratory tract!

Endemic mycoses primary infection

primary infection in the lung, with subsequent dissemination to other organs and tissues.

Superficial mycoses examples

Pityriasis (Tinea) versicolor
Tinea nigra
White piedra
Black piedra

What is Pityriasis (Tinea) versicolor

Common superficial fungal infection seen worldwide.

Most cases of Pityriasis (Tinea) versicolor are (a/symptomatic)

symptomatic

geographical predilection of Pityriasis (Tinea) versicolor

May affect up to 60% of people in some tropical areas

Pityriasis (Tinea) versicolor is

Caused by the lipophilic yeast species of the Malassezia furfur complex

Malassezia furfur complex
examples

M. furfur, M. sympodialis,
M. globosa, M. restricta,
M. slooffiae, M. obtusa,
M. dermatis, M. japonica, and M. yamatoensis.

Pityriasis (Tinea) versicolor appearance

Spherical or oval, thick-walled yeastlike cells, 3 to 8 �m in diameter.

Pityriasis (Tinea) versicolor
epidemiology

-Disease of healthy persons most prevalent in tropical and subtropical regions.
-Young adults are most commonly affected.

Pityriasis (Tinea) versicolor
Clinical manifestations

-Small and irregular hypopigmented or hyperpigmented macules
-Usually covered by a fine scaling
-Hypopigmented macules mostly in dark-skinned people
-Pink to pale lesions more frequent in light-skinned individuals

where are the hyper/hypopigmented macules caused by Pityriasis (Tinea) versicolor mostly seen on?

-Upper trunk
-Arms
-Chest
-Shoulders
-Face
-Neck

Does Pityriasis (Tinea) versicolor activate the immune system?

-Little or no host reaction
-Lesions are asymptomatic, with the exception of mild pruritus (itching) in severe cases

Other syndromes associated with M. furfur complex

-Folliculitis
-Obstructive dacryocystitis
-Systemic infections in patients receiving intravenous lipid infusions and seborrheic dermatitis, especially in patients with the acquired immunodeficiency syndrome (AIDS).

Laboratory diagnosis of Pityriasis (Tinea) versicolor

Direct visualization of the fungal elements on microscopic examination of epidermal scales in 10% potassium hydroxide (KOH) with or without calcofluor white.
Usually numerous organisms

T/F Pityriasis (Tinea) versicolor
can only be seen with gram staining

false
Also visualized with hematoxylin and eosin

Do Pityriasis (Tinea) versicolor show floresence?

The lesions fluoresce with a yellowish color upon exposure to a Wood lamp.

Microscopically, the Pityriasis (Tinea) versicolor colonies are composed of

budding yeastlike cells with occasional hyphae.

What is Tinea nigra caused by

the black fungus Hortaea werneckii.

Epidemiology of tinea nigra

-Tropical or subtropical condition.
-Likely contracted by traumatic inoculation of the fungus into the superficial layers of the epidermis.

geographical predilection of tinea nigra

Most prevalent in Africa, Asia, and Central and South America.

age and gender predilection for tinea nigra

Children and young adults are most often affected, higher incidence in females.

Tinea nigra: clinical syndrome

-Solitary, irregular, pigmented (brown to black) macule.
-Usually on the palms or soles.
-No scaling
-No invasion of hair follicles.
-The infection is not
contagious.
-Asymptomatic
-Little or no host reaction.

What does Tinea nigra resemble?

-The lesion grossly may resemble a malignant melanoma: biopsy or local excision may be considered.
-Simple microscopic examination may avoid such invasive procedures.

Laboratory diagnosis of tinea nigra

-Microscopic examination of skin scrapings placed in 10% to 20% KOH.
-The pigmented hyphae and yeast forms are confined to the outer layers of the stratum corneum and are easily detected on H& E-stained sections.

What is white piedra

Superficial infection of hair.

What is white piedra caused by?

Caused by yeastlike fungi of the genus Trichosporon:

T. ovoides causes

scalp hair white piedra.

T. inkin causes

most cases of pubic white piedra

geographical predilection of white piedra

Tropical and subtropical regions and is related to poor hygiene.

White piedra clinical syndromes

-Affects the hairs of the groin and axillae.
-The fungus surrounds the hair shaft and forms a white to brown swelling along the hair strand.
-The swellings are soft and pasty and may be easily removed.
-No damage of hair shaft.

What is black piedra

Affect the hair, primarily the scalp.

What causes black piedra

Piedraia hortae

Black piedra is (un/common)

uncommon