FFP1L5 Introduction to fungi and fungal infections 2023 PDF

Leading the world to better health  RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Introduction to Fungi and Fungal Infections Class Ye...

Leading the world to better health  RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Introduction to Fungi and Fungal Infections Class Year 1 Course Undergraduate Medicine Lecturer Dr. Muaaz Ather Prof Manaf Al Qahtani Date 22nd October 2023  LEARNING OUTCOMES 1. List the differences between yeast, moulds and dimorphic fungi 2. Classify clinically important fungi and give some examples 3. Describe the different kinds of fungal infection 4. Recognise the clinical features of fungal infections 5. Know the diagnostic techniques used to identify fungi 6. Explain the risk factors for invasive fungal disease  MYCOLOGY The study of fungi  LEARNING OUTCOME 1. List the differences between yeast, moulds and dimorphic fungi 2. Classify clinically important fungi and give some examples  FUNGI Eukaryotes Worldwide (some endemic to specific areas) Can be non-pathogenic, primary pathogens, or opportunistic pathogens. Not susceptible to antibiotics  FUNGAL STRUCTURE Cell Membrane Phospholipid bilayer Surrounds cytoplasm Contains Ergosterol Cell Wall Chitin + carbohydrates (ß-d-glucan and mannans) Chitin cell wall gives rigidity Antigenic Capsule Some fungi Polysaccharide Antiphagocytic virulence factor  CLASSIFICATION OF FUNGI Yeast Mould of Filamentous Fungi Hyphae Spore Dimorphic  SOME DEFINITIONS Hyphae Tubules made up of fungal cells attached end to end Growth = extend in length from tip of tubules Spores The reproducing bodies of moulds  YEAST - E.G CRYPTOCOCCUS Unicellular (spheroid or ellipsoid) Reproduce by budding Moist, mucoid, or waxy colonies YEAST-LIKE FUNGI – E.G CANDIDA ALBICANS Grow partly as yeast and partly as elongated cells resembling hyphae (pseudohyphae) Reproduce by budding Generally creamy white colonies  MOULD OR FILAMENTOUS FUNGI Multicellular Made up of clumps of intertwined branching hyphae Grow by longitudinal extension Produce spores  DIMORPHIC FUNGI Can grow either as a yeast or mould depending on the environmental conditions and temperature o Moulds in environment at 25-30 C o Yeasts in human tissues at 35-37 C WHY IS FUNGAL INFECTION IMPORTANT? More Cases Increasing numbers of vulnerable patients – Chemotherapy – Transplantation – Immunomodulatory therapies More manageable Better diagnostic techniques New anti-fungal agents available  LEARNING OUTCOME 3. Describe the different kinds of fungal infection 4. Recognise the clinical features of fungal infections  AN OVERVIEW OF FUNGAL INFECTION Superficial Invasive – Subcutaneous – Systemic  SUPERFICIAL MYCOSES Limited to outermost layers of skin, hair, nails and mucosa 1. Pityriasis versicolor (pigmented lesions on upper torso) 2. Dermatophytosis (Ringworm/tinea) 3. Candidiasis (Discussed in latter half of lecture) Diagnosis – skin scrapings (KOH - microscopy)  PITYRIASIS VERSICOLOR Malassezia furfur (filamentous fungus) Common – patchy rash Pale brown/pink macules - Pale patches more common in darker skin Itchy Trunk / Neck most common More common in hot, humid climates or if sweat heavily.  DIAGNOSIS Clinical appearance Wood’s Light Skin scrapings  TINEA (RINGWORM) Skin infection caused by dermatophyte fungi 3 genera of dermatophytes: Trichophyton spp Epidermophyton spp Microsporum spp May be acquired from humans/animals/soil  PART OF BODY INFECTED = TINEA INFECTION IS GIVEN A SPECIFIC NAME Tinea barbae (beard) Tinea capitis (head) Tinea corporis (body) Tinea cruris (groin) Tinea faciei (face) Tinea manuum (hand) Tinea pedis (foot) Tinea unguium (nail) TINEA CAPITIS TINEA CORPORIS TINEA PEDIS TINEA MANUUM TINEA UNGUIUM  DIAGNOSIS Clinical – classic appearance T. interdigitale Skin scrapings/nail clippings Microscopy (treat first with M. canis KOH to clear keratin) Culture on selective media - Sabouraud agar T. rubrum  SUBCUTANEOUS MYCOSES Involves deeper layers of dermis and subcutaneous tissue At sites of trauma – acquired from soil / thorns SPOT DIAGNOSIS SPOROTRICHOSIS ‘ROSE PICKERS DISEASE’ Sporothrix schenckii (dimorphic fungus) Initial ulcer develops into granulomatous nodule  CLINICAL SPECTRUM - SPOROTRICHOSIS Cutaneous / Lymphocutaneous Most common Enters through break in skin from touching contaminated plant matter Pulmonary Inhalation of fungal spores Disseminated Spread of infection to other parts of the body – e.g osteoarticular, central nervous system Risk factors: Immunodeficiency, COPD, HIV, Alcohol excess  DIAGNOSIS - SPOROTRICHOSIS Microscopy – KOH Culture (Sabouraud agar) – Tissue biopsy – Sputum – Body fluid Histopathology  DIMORPHIC FUNGAL INFECTION – HISTOPLASMA CAPSULATUM Grow as moulds at 25oC, yeasts at 37oC Not common in Ireland, UK or rest of Europe but found in North America Found in soil Guano from birds & bats Caves!  CLINICAL PRESENTATION Asymptomatic infection Acute/ chronic respiratory infection resembling TB Disseminated, involving liver, lungs, spleen (immunosuppressed patients) Fungus lives intracellular in macrophages => immune-evasion  DIAGNOSIS Antigen detection – Urine and / or serum Culture – Tissue, blood, body fluid – Can take up to 6 weeks Histopathology Microscopy – Low sensitivity Serology So we’ve looked at infections; - Superficial - Cutaneous - Systemic And some fungi that cause them. Now we’ll look at some fungi and see the types of infections they cause i.e. candida, aspergillus,  CANDIDA - PSEUDOYEASTS Normal flora; mouth, intestine and lower genital tract *Opportunist pathogens, (increasing importance) Superficial (skin + mucosal) & systemic infections More in: Introduction to opportunistic infection lecture  CANDIDA – SKIN INFECTIONS Erythema, plaque-like lesions, satellite lesions Warm, moist areas, skin folds - intertrigo (axilla, groin, perineum, under breasts) Precipitants – Antibiotics – Steroids – Pregnancy – Immunosuppression  DIAGNOSIS & TREATMENT Diagnosis: – Clinical appearance – Skin scrapings, swabs Treatment: – Topical antifungal agents: Clotrimazole – Oral: Fluconazole  CANDIDA – MUCOSAL INFECTIONS Discrete white patches on mucosal surface - Oral - Vaginal - Oesophageal (esp. HIV) Diagnosis: Swab for microscopy and culture Treatment: – Topical (Clotrimazole) – Oral antifungal (fluconazole)  CANDIDA – INVASIVE INFECTIONS Candida blood stream infection Infective endocarditis Peritonitis Osteomyelitis Arthritis Endophthalmitis More in: Introduction to opportunistic infection lecture  ASPERGILLUS Mould/ filamentous fungus Found in soil, air, plants and decomposing organic matter Hospital environments: construction work  ASPERGILLUS - PATHOGENESIS Allergy due to reaction to Aspergillus antigens in atopic individuals (ABPA) OR Spore-forming organism – Spores inhaled – Germinate to form hyphae – Destruct blood vessels & disseminate  CLINICAL MANIFESTATIONS 1. Allergic aspergillosis – Sinusitis – Allergic Bronchopulmonary Aspegillosis (ABPA) 2. Aspergilloma 3. Invasive aspergillosis (more in: introduction to opportunistic infection lecture)  ALLERGIC BRONCHO PULMONARY ASPERGILLOSIS Hypersensitivity reaction Asthma, cystic fibrosis Bronchospasm, obstruction Wheeze, cough, SOB, fever Eosinophilia, high IgE Diagnosis –high antibody titres in serum Fleeting CXR changes Treat with steroids +/- itraconazole  ASPERGILLOMA Damaged lung (TB, CF, COPD) Asymptomatic, chronic cough, haemoptysis Sputum positive in 66% Antibodies positive in 70% Fluid filled cavity on CXR/CT Thorax Surgery in some cases No role for antifungals  INVASIVE ASPERGILLOSIS Risk groups – Neutropenia, transplant, HIV Spread from primary site to other sites (liver, spleen, kidney, CNS) Invasion of blood vessels More in: Introduction to opportunistic infection lecture  LEARNING OUTCOME 5. Know the diagnostic techniques used to identify fungi  DIAGNOSTIC TECHNIQUES Diagnosis of fungal infection depends on clinical presentation and exam Diagnostic techniques we have covered to diagnosis fungal infection in this lecture include Clinical diagnosis Microscopy and Culture Antigen detection Serology Histopathology Radiology  LEARNING OUTCOME 6. Explain the risk factors for invasive fungal disease  RISK FACTORS FOR INVASIVE FUNGAL INFECTION Haematological malignancy Haematopoietic stem – cell transplant Solid Organ transplant Neutropenia Extremes of age Abdominal surgery Prolonged ICU admission Central venous catheter Use of broad spectrum antibiotics Renal failure  SUMMARY Yeast, moulds and dimorphic fungi Classification, morphology & pathogenicity We looked at infections in two ways – Superficial, subcutaneous & systemic infections – Candida, Aspergillus Treatment of fungal infections will be covered in the antifungal/antiviral lecture in FFP2 Invasive fungal infections will be covered in further detail in the Introduction to Opportunistic infection lecture in FFP2 Thank you