Subcutaneous and Systemic Mycoses Lecture Notes PDF

Subcutaneous and Systemic Mycoses Lec.4 Subcutaneous Mycoses When fungi are transferred directly into traumatized skin, they can invade. Dimorphic soil organism Worldwide distribution Spread via lymphatics. It may reach distant organs, especially bone, and joints in the path. Most species in this gr...

Subcutaneous and Systemic Mycoses Lec.4 Subcutaneous Mycoses When fungi are transferred directly into traumatized skin, they can invade. Dimorphic soil organism Worldwide distribution Spread via lymphatics. It may reach distant organs, especially bone, and joints in the path. Most species in this group are greatly inhibited by higher temperatures of the blood and viscera. Diseases are progressive Sporothrix Schenckii Sporotrichosis (rose-gardener’s disease) Very common saprobic fungus that decomposes plant matter in soil. Infects appendages and lungs. Splinters or thorns inoculate organism into subcutaneous tissues. Lymphocutaneous variety occurs when contaminated plant matter penetrates the skin and the pathogen forms a nodule, then spreads to nearby lymph nodes The microscopic morphology of Sporothrix schenckii Clinical appearance of lymphocutaneous sporotrichosis Cutaneous sporotrichosis of a cat's paw showing ulcerations. The first symptom of cutaneous sporotrichosis is a small skin lesion. These lesions may show ulceration and/or erythema. Commonly, infection spreads through the lymph along lymphatic vessel and causes lymphocutaneous sporotrichosis. This form of disease is characterized by the appearance of lesions at sites distant to the initial infection. Systemic Infections Systemic mycoses are fungal infections affecting internal organs. ⦿ Fungi enter the body via lungs, through the gut, para-nasal sinuses or skin ⦿ Then spread via bloodstream to multiple organs including the skin ⦿ Can cause a tremendous variety of health problems including digestive difficulties, skin problems , asthma, breathing difficulties etc. ⦿ Often causing multiple organs to fail and eventually resulting in the death of the patient ⦿ Systemic mycoses is of two types – ◾Systemic mycoses due to primary pathogens ◾Systemic mycoses due to opportunistic pathogens Systemic mycoses due to primary pathogens Originate primarily in the lungs and may spread to many organ systems ⦿ Pathogens are dimorphic ⦿ Also known as endemic respiratory infections. These are mainly of 4 types ⦿ ◾ Histoplasma capsulatum (causing histoplasmosis) ◾ Coccidioides immitis (causing coccidioidomycosis) ◾ Blastomyces dermatitidis (causing blastomycosis) ◾ Paracoccidioides brasiliensis (causing paracoccidiodomycosis) Histoplasmosis: Ohio Valley Fever Histoplasma capsulatum – most common true pathogen; causes histoplasmosis Distributed worldwide, most prevalent in eastern and central regions of U.S. Grows in moist soil high in nitrogen content Inhaled conidia produce primary pulmonary infection that may progress to systemic involvement of a variety of organs and chronic lung disease Amphotericin B, ketoconazole Dimorphic colonies of Histoplasma capsulatum SymptomsFever, chills, headache, dry cough, chest discomfort, liver enlargement etc. Coccidioidomycosis: Valley Fever Coccidioides immitis – causes coccidioidomycosis Distinctive morphology – block like arthroconidia in the free-living stage and spherules containing endospores in the lungs Lives in alkaline soils in semi arid, hot climates and is endemic to southwestern U.S. Arthrospores inhaled from dust, creates spherules, and can form nodules in the lungs Amphotericin B treatment Events in Coccidioides infection Disseminated coccidioidomycosis SymptomsRashes, myalgia, shortness of breath, weight loss, night sweats, influenza etc. Blastomyces dermatitidis: North American Blastomycosis Blastomyces dermatitidis – causes blastomycosis Free-living species distributed in soil of a large section of the mid western and southeastern U.S. Inhaled 10-100 conidia convert to yeasts and multiply in lungs. Symptoms-Fever, chills, cough, muscle ache, joint pain, chest pain etc. Chronic cutaneous, bone, and nervous system complications Amphotericin B The dimorphic nature of Blastomyces dermatitidis Cutaneous blastomycosis in the hand and wrist Caused by Paracoccidioides brasiliensis ⦿ Acute or chronic, granulomatous infection primarily of lungs & disseminates to skin, mucosa & other internal organs. ⦿ SymptomsAcute pneumonia TreatmentLong term therapy ▪ Amphotericin B combined with sulfonamides ▪ Oral Itraconazole ▪ Systemic mycoses due to opportunistic pathogens ⦿ Fungi that only result in systemic infection in immunecompromised or sick people. ⦿ Examples of immune compromised conditions include AIDS, alteration of normal flora by antibiotics, immunosuppressive therapy, and metastatic cancer. ⦿ Its main types are◾ Candida species (causing candidiasis) ◾ Aspergillus species (causing aspergillosis) ◾ Cryptococcus (causing cryptococcosis) ◾ Zygomycetes (causing zygomycosis) Infections by Candida: Candidiasis Caused by yeast- like fungi of genus Candida albicans Widespread yeast It is of 2 types- Infectious and Allergic Budding cells of varying size that may form both elongate pseudohyphae and true hyphae Forms off-white, pasty colony with a yeasty odor Candida albicans Normal flora of oral cavity, genitalia, large intestine or skin of 20% of humans. Account for 70% of nosocomial fungal infections. Oropharyngeal (Thrush) – occurs as a thick, white, adherent growth on the mucous membranes of mouth and throat Vulvovaginal yeast infection – painful inflammatory condition of the female genital region that causes ulceration and discharge Cutaneous candidiasis – occurs in chronically moist areas of skin and in burn patients Infections by Candida albicans oral candidiasis Diagnosis and Treatment Presumptive diagnosis made if budding yeast cells and pseudohyphae are found; germ tube Growth on selective, differential media differentiates Candida species Topical antifungals for superficial infections, amphotericin B and fluconazole for systemics Detection of Candida albicans 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 Cryptococcosis Symptomspneumonia like illness, shortness of breath, skin lesions may occur, fever, cough etc. Diagnosis and Treatment Negative stain demonstrating encapsulated budding yeast Biochemical tests, serological testing Systemic infection requires amphotericin B and fluconazole C. neoformans stained by India ink Mucoid colonies of C. neoformans Aspergillosis: Diseases of the Genus Aspergillus Very common airborne soil fungus 600 species, 8 involved in human disease; A. fumigatus most commonly Serious opportunistic threat to AIDS, leukemia, and transplant patients Infection usually occurs in lungs – spores germinate in lungs and form fungal balls; can colonize sinuses, ear canals, eyelids, and conjunctiva Invasive aspergillosis can produce necrotic pneumonia, and infection of brain, heart, and other organs Amphotericin B and nystatin Clinical aspects of aspergillosis Symptomssuperficial lesions, coughing up of blood, chest pain, etc. Microscopic appearance of Aspergillus ⦿ The most reliable tests to confirm infection are skin biopsy for histological (microscopic) analysis, and fungal culture. ⦿ Blood can also be cultured. Fig :- culture of Histoplasma capsulatum (histoplasmosis)