lec.7 Opportunistic mycosis

MycologyLec,7

Opportunistic mycosis Dr.Huda Ibrahim

Oppurtunistic mycosis

Ordinary fungi causing extraordinary disease Infections due to fungi of low virulence in patients who are immunologically compromised

Opportunistic fungi

1. Saprophytic - from the environment e.g.,Cryptococcus sp. , Aspergillus, Zycomycetes.2. Endogenous – a commensal organism e.g., Candida sp. Include many species from: A (Aspergillus)To Z (Zygomyces)

*

Predisposing Factors: Providing a Route/ Source

Antibiotics Burns and other skin problems Catheter- related problems Devices (prosthetic) Effects on mucosal integrity Fungus isolated previously

Inducing Immunosuppression

AIDS Bone marrow/ organ transplantation Cancer: Leukemia, lymphoma etc Drugs: Cytotoxic drugs,steroids etc Endocrine related: Diabetes Failure of organs: multi-organ


Candida albicans and other Candida species
Harmless inhabitants of the skin and mucous membranes of all humans Normal immune system keeps candida on body surfaces

THE MOST IMPORTANT RISK FACTORS

1. Neutropenia(less than 100 N/L) 2. Diabetes mellitus 3. AIDS 5. Myeloperoxidase defects 6. Broad-spectrum antibiotics

THE MOST IMPORTANT RISK FACTORS

7. Indwelling catethers 8. Major surgery 9. Organ transplantation 10. Neonates 11. Severity of any illness 12. Intravenous drug addicts

INVASIVE CANDIDIASIS

If phagocytic system is compromised, infection spreads to many organs and causes focal infection in these organs (kidney ,eye ,heart , liver , meninges) mortality of candidemia is 30-40% Prophylactic antifungal drugs during cytotoxic course of therapy

DIAGNOSIS OF INVASIVE CANDIDIASIS

Gram stain and isolation from blood, CSF , urine ,sputum or peritoneal fluid Serology PCR (promising) isolation and/or pathology positive of organ involved

EPIDEMIOLOGY

Although candidiasis is endogenous in most cases, cross infections are described, especially in intensive care unit patients. Account for 80% of nosocomial fungal infections Account for 30% of deaths from nosocomial infections


* Cryptococcosis and Cryptococcus neoformans
Cryptococcus neoformans causes cryptococcosis. A widespread encapsulated yeast that inhabits soil around pigeon roosts Common infection of AIDS, cancer or diabetes patients Infection of lungs leads to cough, fever, and lung nodules Dissemination to meninges and brain can cause severe neurological disturbance and death.

Pulmonary Cryptococcus

Diagnosis
Microscopic India Ink for capsule stain (50-80% + CSF) Gram Calcoflur white Silver stain Culture Bird seed agar Routine blood culture

Diagnosis

SerologyLatex agglutination, EIA, 90% sensitive & specificRadiologyCXR – infiltrates, nodules, lymphadenopathy, cavitation, effusionCT/MRI – 50% normal, hydrocephalus

Therapy – Cryptococcal meningitis Amphotericin B +/- flucytosine Fluconazole Amphotercin x 2 wk then fluconazole 400-800 mg/d x 8-10 wk Chronic suppression fluconazole 200 mg/d

* Aspergillosis: Diseases of the Genus Aspergillus

Very common airborne soil fungus600 species, 8 involved in human disease; A. fumigatus most commonlySerious opportunistic threat to AIDS, leukemia, and transplant patientsInfection usually occurs in lungs – spores germinate in lungs and form fungal balls; can colonize sinuses, ear canals, eyelids, and conjunctivaInvasive aspergillosis can produce necrotic pneumonia, and infection of brain, heart, and other organs.Amphotericin B and nystatin

* Zygomycosis

Zygomycota are extremely abundant saprophytic fungi found in soil, water, organic debris, and food. Genera most often involved are Rhizopus, Absidia, and Mucor. Usually harmless air contaminants invade the membranes of the nose, eyes, heart, and brain of people (Rhinocerebral mucormycosis) with diabetes and malnutrition, with severe consequences. main host defense is phagocytosis


Diagnosis is made by direct smear and by isolation of molds from respiratory secretions or biopsy specimens. Treatment: Control Diabetes ,surgery & amphotericin B Prognosis: very poor

Diagnosis of opportunistic infections requires a high index of suspicion

Atypical signs or symptomsUnusual organ affinityOutside the endemic areaUnusual HistopathologyEtiologic agent may be a “saprophyte”Serological response may be suppressed

A typical sign & symptoms

Malasezzia furfur Tinea versicolor (mild disease in normal person) can cause disseminated infection--------Particularly in patients receiving hyperalimentation (compromsed pt..

Unusual organ affinity

Immunocompromised patients can develop hepatic candidiasis

Liver infected with Candida albicans

Outside Endemic Area
Disseminated coccidioidomycosis, Histoplasmosis (not pulmonary)

Unusual Histopathology

NORMAL HOST PYOGENIC GRANULOMATOUS IMMUNODEFICIENT HOST NECROTIC


Unusual pathogen
Penicillium marneffei Usually not a pathogen The only dimorphic penicillium Produces a red pigment Endemic in the Far East

IMPROVING TREATMENT

New Drugs New therapeutic regimen Aggressive therapy Conjunctive therapy

IMPROVING TREATMENT

New Drugs Lipid Amphotericin B Third generation azoles (Posaconazole, Voriconazole) New classes of antifungal agents (Echinocandins)

IMPROVING TREATMENT

New Therapeutic Regimen Combination Therapy Simultaneously administering two drugs Sequential Tx with two or more drugs Alternate Administration of two or more

IMPROVING TREATMENT

AGGRESSIVE THERAPYFOR IMMUNOCOMPROMISED PATIENTSProphylactic – Anti-fungal agents at, or near, the time of chemotherapyFluconazole , Posaconazole now approved.

IMPROVING TREATMENT

CONJUNJUNCTIVE THERAPY FOR IMMUNOCOMPROMISED PATIENTS The use of anti-fungal agents with immunotherapy: *Interferons Colony stimulating factors Interleukins

OPPORTUNISTIC FUNGAL INFECTIONS ARE:

difficult to diagnose difficult to treat difficult to prevent more and more frequent a great challenge for a future work in all fields



“Only the prepared mind can help the impaired host”Libero Ajello, Chief Mycology Division, CDC 1972

MYCOLGISTS have more

FUNGI