OPPORTUNISTIC MYCOSES

OPPORTUNISTIC MYCOSESGeneral features

CAUSATIVE AGENTSSaprophyte in nature/found in normal flora

HOST Immunosupressed /other risk factors

• Candidiasis• Cryptococcosis (discussed)• Aspergillosis• Zygomycosis• Other: Trichosporonosis, fusariosis,

penicillosis……***ANY fungus found in nature may give

rise to opportunistic mycoses ***

OPPORTUNISTIC MYCOSES

• Most commonly encountered opportunistic mycoses worldwide

• Cellular immunity protects against mucocutaneous candidiasis, neutrophiles protect against invasive candidiasis

• Endogenous infection. • Etiology: Candida spp. Most common:

1. C. albicans 2. C. tropicalis 3. C. glabrata

CANDIDIASIS

Candida

MORPHOLOGICAL FEATURES

• Micr. Budding yeast cells Pseudohyphae, true hyphae

• Macr. Creamy yeast colonies (SDA)• Germ tube (C. albicans, C.

dubliniensis)• Chlamydospore (C. albicans, C.

dubliniensis)• Identification Germ tube, fermentation

Macroscopic Morphology Yeast colony. Sabouraud Dextrose agar (DSA)

Candida albicans

Candida albicans Microscopic Morphology

Yeast cells and pseudohyphae in material from the oral cavity, KOH

preparation, phase-contrast microscopy

Candida

PATHOGENICITY • Attachment (Germ tube is more

adhesive than yeast cell)• Adherence to plastic surfaces

(catheter, prosthetic valve..)• Protease• Phospholipase

CANDIDIASISRisk factors

• Physiological. Pregnancy, elderly, infancy

• Traumatic. Burn, infection• • Hematological. Cellular immune deficiency, AIDS, chronic

granulamatous disease, aplastic anemia, leukemia, lymphoma...

• Endocrinological. DM

• Iatrogenic. Oral contraceptives, antibiotics, steroid, chemotherapy, catheter...

CANDIDIASISClinical manifestations-I

1. CUTANEOUS and SUBCUTANEOUS• Oral• Vaginal • Onychomycosis• Dermatitis• Diaper rash

Candida albicans Clinical Presentation

The white material are masses of the yeast

The presence of satellite lesions help makes the

diagnosis of diaper rash.

CANDIDIASISClinical manifestations-II

• Esophagitis• Pulmonary inf.• Cystitis• Pyelonephritis• Endocarditis• Myocarditis

• Peritonitis• Hepatosplenic• Endophthalmitis • Osteomyelitis• Menengitis• Skin lesions

2. SYSTEMIC

CANDIDIASISClinical manifestations-III

3. CHRONIC MUCOCUTANEOUS• Candida inf. of skin and mucous

membranes • Verrucose lesions• Impaired cellular immunit• Hypoparathyroidism, iron

deficiency

Candida albicans Granulomatous lesions involving the hands.

CANDIDIASISDiagnosis

• Direct micr.ic examination Yeast cells, pseudohyphae, true hyphae• Culture SDA, routine bacteriological media• Serology Detection of mannan antigen (ELISA, RIA, IF, latex agglutination)

CANDIDIASISTreatment

• CUTANEOUSTopical antifungal: Ketoconazole, miconazole, nystatin• SYSTEMIC Amphotericin B Fluconazole, itraconazole• CHRONIC MUCOCUTANEOUSAmphotericin BFluconazole, itraconazoleTransfer factor

Causative Agent• Aspergillus fumigatus• Aspergillus flavus• Aspergillus niger- mostly local infection;

otomycosis• Are molds that have septate hyphae with V-

shaped branches (Fruiting body of Aspergillus)

Source of infection• Widely distributed in environment• Transmitted by air-borne light spores• High environmental load is associated with sick

building syndrome & contaminated AC system

Aspergillosis

Systemic infection

Aspergillus

Pathogenesis & Clinical featuresAspergillus can colonize and invade:• Lungs • Wounds, burns • Cornea• External ear • Paranasal sinuses

Aspergillosis

In lungs can cause:a) Hypersensitivity Reaction: Spores colonise RT without invasion and lead toallergic asthma, rhinitis, bronchopulmonary aspergillosis

b) Aspergilloma (fungus ball): the spores colonise paranasal sinuses or a pre-existing cavity in lung (TB cavity)The radiological appearance may be similar to malignancy.

c) Invasive AspergillosisIn immunocompromised can invade lungs causing hemoptysis & granuloma and disseminate to other organs Fatality rate 100% if not diagnosed and treated promptly.

Aspergillosis

Lab DiagnosisSpecimens : sputum, BM aspirate, biopsyDirect Microscopy• Shows branching septate hyphaeCultures : Microscopy shows radiating chains of sporesSerology• In allergic condition: high levels of specific IgE• Galactomannan in invasive aspergillosisTreatment• Invasive aspergillosis

Amphotericin B• Allergic conditions

Steroids & antifungals

Aspergillosis

ZygomycosisMucormycosis

• Causative agents; saprophtic molds• Rhizopus, Mucor & Absidia• Have broad, aseptate hyphae• Have large no. of asexual spores inside a sporangium

• Risk factors Diabetic ketoacidosis, immunosuppression

• Pathogenesis Inhalation of sporangiospores

• Infected tissue vascular invasion, thrombus, infarct,

ZYGOMYCOSISClinical manifestations

I. RHINOCEREBRAL• Nose, paranasal sinuses, eye, brain and meninges are

involved• Orbital cellulitis II. THORACIC• Pulmonary lesions, parenchymal necrosisIII. LOCAL• Posttraumatic kidney inf.• Skin inf. following burn or surgery

ZYGOMYCOSIS Diagnosis

• Samples Sputum, BAL, biopsy of paranasal sinuses..

• Direct exam. Nonseptate, ribbon-like hyphae which branch at right angles, sporangium

• Culture SDA (cotton candy appearence)

Rhizopus

Diseases• Rhinocerebral zygomycosis

o Extensive cellulitis of nasal mucosa, paranasal sinuses, orbit & brain

o Rapidly fatal• Pulmonary & disseminated infectionsTreatment• Surgical debridement

• Amphotericin B

***High mortality rate

ZygomycosisMucormycosis

Fusariosis

• Fusarium species, have been increasingly recognized as lethal pathogens

• ~50 different species of the Fusarium • Only a few human pathogens• The skin and respiratory tract are the

primary portals of entry for Fusarium infection

• Fusarium spp. are angiotropic and angioinvasive molds that lead to hemorrhagic infarction, low tissue perfusion, and resultant tissue necrosis

Fusariosis

Infections in normal hosts• Are typically localized like skin, eye infections and

osteomyelitis • Frequently do not require systemic therapy

Infections in immunocompromised patients

Manifest in four major patterns: • Refractory PUO • Pulmonary infection or pneumonia • Disseminated infection• A variety of focal single-organ infections

• Fusarium is one of the most resistant fungi to the arsenal of modern antifungal agents

• The mainstay in the treatment is Ampho-B

• In vitro susceptibility of Fusarium spp. to Ampho-B is, at best, mediocre

Fusariosis

Invasion of the cornea by a Fusarium species

Endophthalmitis due to a Fusarium species

Macroscopic Morphology of Fusarium species