2Learning ObjectivesAt the end of the lesson, students will be able to:Discuss how fungi cause diseasesCompare and contrast superficial, cutaneous, subcutaneous, systemic and opportunistic mycoses in terms of characteristics/definition, example of diseases it may cause and its causative agent and laboratory diagnosis
3How do fungi cause disease? Growth on body surfaces.Invasion of the body.Allergic reactions.Toxins released after ingestion
4CLASSIFICATION OF FUNGAL INFECTIONS Mycoses: fungal diseases.Tend to be chronic because fungi grow slowly.Fungal diseases are classified into 4 groups:Superficial mycosesCutaneous mycosesSubcutaneous mycosesDeep (systemic) mycoses
5Example & Causative Agent SuperficialCutaneousDefinitionInfection that do not involve a tissue responseInfections of the skin, hair & nailsExample & Causative AgentPityriasis: dermatitis characterized by redness of the skin and itching caused by Malassezia furfurOnychomycoses (Tinea ungium) : nail infections caused by Candida albicans or a dermatophytesRingworm(Tinea capitis)Athlete’s foot(Tinea pedis)Jock itch(Tinea cruris)Favus: destruction of the hair follicle caused by Trichophyton schonleiniLab DiagnosisDirect Microscopy: 10% KOH is used to digest the skin debris(bottle shaped budding yeast cells)PCR & other molecular methodsDirect Microscopy: septate branched hyphaeCultureSDA(Sabourauds dextrose agar medium is used)Creamy colonies appearSDAHoney-combed like thallus(cream colored to yellow brown)
6Example & Causative Agent SubcutaneousSystemicDefinitionInfections beneath the skinInfections deep within the bodyExample & Causative AgentSporotrichosis: chronic infection of the subcutaneous tissues and adjacent lymphatics characterized by nodular lesions(Sporothrix schenkii)Histoplasmosis (Histoplasma capsulatum): Initial infection in lungs. Later spreads through blood to most organs.Coccidiomycosis (Coccidioides immites): a dimorphic fungus. Resembles tuberculosisLab DiagnosisDirect Microscopy: Tissue sections should be stained usingGrocott's methenamine silver (GMS)Gram stainInterpretation: Look for small narrow base budding yeast cells (2-5um).Clinical material- Skin scrapings, sputum and bronchial washings, cerebrospinal fluid, pleural fluid and blood, bone marrow, urine and tissue biopsies from various visceral organs.2. Direct Microscopy:Skin scrapings should be examined using 10% KOH and Parker ink or calcofluor white mounts.Exudates and body fluids should be centrifuged and the sediment examined using either 10% KOH and Parker ink or calcofluor white mounts.Tissue sections should be stained using PAS digest, Grocott's methenamine silver (GMS) or Gram stain.CultureSabouraud dextrose agar and Brain heart infusion agar supplemented with 5% sheep bloodSDA
7FUNGAL DISEASESOpportunistic mycoses: Caused by organisms that are generally harmless unless individual has weakened defenses:AIDS and cancer patientsIndividuals treated with broad spectrum antibioticsVery old or very young individuals (newborns).Examples:Aspergillosis: Inhalation of Aspergillus spores.Yeast Infections or Candidiasis: Caused mainly by Candida albicans. Part of normal mouth, esophagus, and vaginal flora.
8Opportunistic Fungi Mycoses Candidia albicansa common unicelluar fungus which is part of the flora of the oral cavity, vagina, and gastrointestinal tract;They become opportunist especially in immunocompromised peopleOral candidiasis (Oral thrush)Classic thrush is characterised by a white, curd-like coating on the tongue or elsewhere in the oral cavity. Stomatitis due to Candida is often associated with painful infection of the lips - and corners of the mouth.
9Genital or perigenital candidiasis ((vulvo vaginitis) (vulvo)vaginitis due to Candida .Contamination of the vagina with Candida stems from the endogenous endosaprophytic flora of the gastro- intestinal tract.Diagnosesin culture, it grows as blastospores, pseudohyphae, and septate hyphaecandidiasis the collective term for infection involving Candidacutaneousvaginalsystemic