Fungal infections

Dr. Manisha Tambekar

Fungal infection

• Fungal infections are called mycoses.• Fungi are eukaryotes that grow by budding

( yeasts) or by filamentous extentions called (molds)

• Candida albicans produce buds that fail to detach become elongated, producing a chain of elongated yeast cells called pseudohyphae.

Structure

• Main body: made up of fine, branching colorless threads called hyphae.

• An individual fungal filament is called hypha.• Several of these hyphae, all interwining to

make up a tangled web called the mycelium.

Morphological Classification

• Moulds : hyphae in form. Eg: ringworm or dermatophytes.

• Yeasts : Single cell that bud to reproduce. Eg: cryptococcus neoformans.

• Yeast like: Form Pseudohyphae. Eg: candida albicans.

• Dimorphic fungi: have both a yeast form ( at human body temp) and a mold form ( at room temp ) eg: Blastomyces dermatitides.

Classification

• According to pathogenicity

1.Superficial mycoses

2.Mucocutaneous mycoses

3.Subcutaneous mycoses

4.Deep Mycoses / systemic.

Candidiasis

• Resides in the skin, mouth, GIT & vagina.• Healthy people: live as benign commensals &

produce no disease.• Candida albicans : frequent cause of human

fungal infections. • Candida albicans grows on warm, moist surfaces

causing oral thrush, vaginitis & diaper rash.• Diabetic & burn patients are prone to superficial

candida.

Candidiasis

• Directly introduced into the blood by IV lines, catheters, peritoneal dialysis, cardiac surgery or IV drug abuse.

• Disseminated candidiasis: Asso. with neutropenia.

• Secondary to leukemia or anticancer therapy, immunosupression after transplantation 7 neutrophil disorders.

• Causes shock & DIC.

Candidiasis

• Tissue sections: appears as yeastlike & pseudohyphae.

• Pseudohyphae: imp diagnostic clue for C. albicans & represent budding yeast cells joined end to end at constrictions.

• Special stains : GMS ( gomori methenamine –silver) & PAS ( periodic acid schiff)

Candidiasis

• Oral thrush: superficial infection on mucosal surfaces of the oral cavity.

• Gray-white, dirty looking pseudomembranes composed of matted organisms & inflammatory debris.

• Mucosal hyperemia &inflammation.• Commonly seen in newborns, debilitated pts.,

children receiving oral steroids for asthma & following a course of antibiotics that destroy competing normal bacterial flora & in HIV.

Oral thrush

Candida esophagitis

• Commonly seen in AIDS patient & with hematolymphoid malignancy.

• Dysphagia, retrosternal paining.

• Endoscopy: white plaques & pseudomembranes resembling oral thrush.

Candidiasis

Candida esophagitis

Budding yeast

Candida vaginitis• Common infection in diabetics or pregnant or

on oral contraceptive pills.• Intense itching & a thick curd like discharge.

Chronic mucocutaneous candidiasis• Chronic refractory disease afflicting mucous

membranes, skin, hair & nails.• Asso. with underlying T-cell defect.

Cutaneous candidiasis• Present in different forms• Infection of nail proper :Onychomycosis• Nail folds : Paronychia• Hair follicles: folliculitis.• Moist, intertriginous skin such as armpits or

webs of the fingers and toes : intertigo & penile skin : Balanitis

• Diaper rash : seen in the perineum of infants , in the region of contact of wet diapers.

Invasive candidiasis• Caused by blood- borne dissemination of

organisms to various tissues or organs.• Common patterns :

1.Renal abscesses

2.Myocardial abscesses & endocarditis ( occurring in the setting of prosthetic valves or in IV drug users).

3.Meningitis with parenchymal micro abscesses

4.Endopthalmitis

Invasive candidiasis

5. Hepatic abscesses

6. Candida pneumonia: B/L nodular infiltrates.

occurs in patient with acute leukemia's who are neutropenic post-chemotherapy.

Cryptococcosis

• Cryptococcus neofarmans: encapsulated yeast ,causing meningoencephalitis in normal individuals

• As opportunistic infection in pts. With AIDS, leukemia, lymphoma, SLE, Hodgkin’s lymphoma or sarcoidosis & in transplant recipients.

• Present in soil & in bird (pigeon) droppings & infects pts when it is inhaled.

Cryptococcosis

• It has yeast but not pseudohyphal or hyphal forms.

• It has thick gelatinous capsule, valuable for diagnosis.

• Capsular polysaccharites stains intense red with PAS and mucicarmine in tissues and detected with antibody-coated beads in an agglutination assay.

Cryptococcosis

• India ink preparations create a negative image, visualizing thick capsule as a clear halo within a dark background, do not stain the yeast.

• Lung – primary site of localization, mild asymptomatic, forms solitary pulmonary granuloma.

• CNS: Involving meninges, cortical gray matter and basal nuclei.

Cryptococcosis

• In imunosuppressed gelatinous masses of fungi grow in the meninges or expand perivascular Virchow-Robin spaces within gray matter producing so-called soap-bubble lesions.

• In non imunosuppressed patients or in those with protracted disease fungi induce a chronic granulomatous reaction composed of macrophages, lymphocytes and FB type giant cells.

• In severely imunosuppressed: may disseminate widely to skin, liver, spleen, adrenals and bones.

In lymphnode: mucicarmine stsain

India Ink

Aspergillosis

• It is a ubicutous mold that causes allergies (brewer’s lung) and sinusitis, pneumonia and fungemia in imunosuppressed patient.

• Factors that predispose to aspergillus infectuon are neutropenia and corticosteroids.

• They are transmitted by air-borne conidia, and the lung is the major portal of entry.

Colonizing aspergillosis (aspergilloma)

• Implies growth of fungus in pulmonary cavities with minimal or no invasion of the tissues.

• Cavities result from pre-existing tuberfungal hypculosis, bronchitctasis, old infarcts, or abscesses.

• Prolifarating masses of fungal hyphae called fungal balls form brownish masses lined free within cavities. Chronic inflammation and fibrosis may also seen.

Invasive aspergillosis

• An opportunistic infection confined to immunosuppressed and devilitated hosts.

• Priamry are seen in lung.• Hematogenous dissemination involves heart

valves, brain and kidneys.• Pulmonary lesions: necrotizing pneumonia

with sharply delineated, rounded, gray foci with hemorrhagic borders referred to as target lesions.

Invasive aspergillosis

• Aspergillus forms fruiting bodies and septate filaments branching at acute angles(40 degree).

• They invade blood vessels.

Aspergillosis...

Aspergillosis : Grocott's methenamine silver GMS stained .

Zygomycosis (mucormycosis)

• Opportunistic infection caused by bread mold fungi. These fungi are widely distributed in nature and cause no harm to healthy individuals.

• They infect immunosuppressed patients. • Predisposing factors: neutropenia CS use, DM

and breakdown of cutaneous barrier (example burns, surgical wounds, trauma).

Zygomycosis (mucormycosis)

• Transmitted by air-borne asexual spores. • Inhaled spores produce infection in sinuses and

lungs.• They form nonseptate, irregularly wide fungal

hyphae with frequent right-angle branching. • Primary sites of invasion are nasal sinuses, lungs and

GIT. • In diabetics fungus spread from sinus to the orbit

and brain giving rise to rhinocerebral mucormycosis.

Zygomycosis (mucormycosis)

• They cause local tissue necrosis, invade arterial walls and penetrate periorbital tissues and cranial vault.

• Meningoencephalitis follows, cerebral infections and induced thrombosis.

• Lung: hemorrhagic pneumonia with vascular thrombi and distil infarctions.

mucormycosis

mucormycosis

Histomorphological characteristic of aspergillosis & mucormycosis

Characteristic Aspergillus Mucormycosis

Width Narrow ( 3-6 µm) Wide (5-20 µm)

CaliberUniform Varying

Branching Regular ( acute angle) Random ( Right angle)

Branching orientation Parallel/radial Random

Septum Common finding uncommon