VIEWS: 285 PAGES: 17 POSTED ON: 9/29/2008
Aspergillosis Lacto-phenol cotton blue Malt Extract Agar Kumuda Sharma Aspergillus species Etiology Aspergillus fumigatus Aspergillus flavus Aspergillus niger Aspergillus tereus are the species most frequently involved in human disease. Properties Exists only as molds Not dimorphic Septate hyphae (form V-shaped branches – dichotomous) The arrangement of sterigmata and conidia aid in differentiating the species Aspergillus sp. Grow rapidly in all types of microbiologic media Pathogenesis 1. Aspergillosis is caused by inhalation of - Aspergillus conida or Mycelial fragments which are present on decaying matter, soil or air 2. 3. When the host defense is compromised Three clinical forms of systemic aspergillosis 1. Respiratory Disease A. Aspergillus asthma – Hypersensitivity to aspergilli may occur in atopic individuals following inhalation of spores Bronchopulmonary aspergillosis – Fungus grows within the lumen of the bronchioles, which may be occluded by fungus plugs Aspergilloma – Fungus colonizes in the pre-existing pulmonary cavities such as in TB or cystic disease, it is called fungus balls (granulomatous mass) B. C. Aspergilloma Or Colonizing aspergillosis 2. Invasive aspergillosis Invasive or disseminated aspergillosis occurs in severely immunocompromised individuals The fungus first establishes in lung tissue Then disseminates to involve other organs particularly brain, kidney and heart Hematogenous spread Symptoms may include cough, fever, night sweats, weight loss, and malaise 3. Superficial infections Sinusitis – A. flavis and A. fumigatus Mycotic keratitis - A. flavis and A. fumigatus Otomycosis – Species of aspergillus, particularly A. niger Toxicosis – in animals and humans has been attributed to several toxins produced by aspergilli. The aflatoxins produced by some strains of A. flavus growing on grains can cause hepatocarcinoma Laboratory Diagnosis 1. Specimens – sputum, bronchoalveolar lavage, biopsy Direct microscopy – KOH preparation of specimen, biopsy section can be stained with H&E and PAS Staining - Lacto-phenol cotton blue stain is also done Culture – Growth on SDA slope (Sabouraud glucose agar) A.fumigatus – green; A.niger – black; A.flavus – golden yellow colored colonies 2. 3. 4. Diagnosis Cont… A. Bronchopulmonary aspergillosis 1. Allergic bronchopulmonary aspergillosis is often diagnosed by skin testing and precipitating Ab titers 2. Bronchial washings are useful in diagnosis of bronchopulmonary aspergillosis B. Aspergilloma They are visible on radiographic examination C. Disseminated aspergillosis 1. Very difficult to diagnose. Blood and other body fluids generally are negative for culture 2. No skin test antigens are available to aid in diagnosis Invasive Pulmonary Aspergillosis in leukemia Bilateral diffused invasive pulmonary aspergillosis, proven by transbronchial biopsy after resolution of neutropenia. Patient treated with oral itraconazole 400mg daily with a good outcome. Treatment Oral corticosteroids: The goal in treating allergic bronchopulmonary aspergillosis is to prevent existing asthma or cystic fibrosis from becoming worse. Antifungal medications by themselves aren't helpful for allergic aspergillosis, but they may be used in combination with corticosteroids to reduce the dose of steroids and improve lung function. Antifungal medications: These drugs are the standard treatment for invasive pulmonary aspergillosis. Historically, the drug of choice has been amphotericin B, but the newer medication voriconazole is now preferred because it appears more effective and may have fewer side effects. Other drugs that can be used are caspofungin, flucytosine, itraconazole Case Study A 38 year old male receiving cytotoxic chemotherapy (immunosuppressed) for leukemia presents with pleuritic chest pain, hemoptysis, fever and chills. He also complains of dyspnea, tachypnea and productive cough VS: fever. PE: severe respiratory distress; bilateral rales heard over lungs. CBC: severe neutropenia. Negative blood and sputum culture for bacteria CXR: necrotizing bronchopneumonia; multiple nodular infiltrates with cavitating lesion frequently crossing lung fissures (FUNGUS BALL) Case Study Contd… GROSS PATHOLOGY: necrotizing bronchopneumonia; abscess MICRO PATHOLOGY: lung biopsy identifies Aspergillus with septate, acutely branching hyphae (visualized by silver stains); necrotizing inflammation; vascular thrombi with hyphae (due to blood vessel invasion) Treatment Amphotericin B with flucytosine; lobectomy for fungus ball Discussion The most lethal form of infection, invasive aspergillosis, is seen primarily in severely immunocompromised individuals, i.e.: patients with AIDS; patients with prolonged, severe neutropenia following cytotoxic chemotherapy; patients with chronic granulomatous disease; and patients receiving glucocorticoids and other immunosuppressive drugs (e.g transplant recipients) Thank You!
Pages to are hidden for
"Aspergillus - PowerPoint"Please download to view full document