Medical Microbiology: Mycology 2023 PDF

MEDICAL MICROBIOLOGY MYCOLOGY HS 4310 Karen Clatt, M. Ed., MLS(ASCP) GENERAL ▪ Predisposing factors: ▪ Immunosuppressive therapy ▪ Broad-spectrum antibiotics ▪ Long-term catheterization ▪ Radiation ▪ Disease ▪ Diabetes mellitus ▪ Neoplasm GENERAL ▪ Methods of examination ▪ Gra...

MEDICAL MICROBIOLOGY MYCOLOGY HS 4310 Karen Clatt, M. Ed., MLS(ASCP) GENERAL ▪ Predisposing factors: ▪ Immunosuppressive therapy ▪ Broad-spectrum antibiotics ▪ Long-term catheterization ▪ Radiation ▪ Disease ▪ Diabetes mellitus ▪ Neoplasm GENERAL ▪ Methods of examination ▪ Gram stain ▪ KOH ▪ Lactophenol cotton blue stain ▪ India ink stain EXAMINATION Gram Stain EXAMINATION ▪ KOH ▪ 10% to 20% KOH ▪ Allows visualization of yeast & hyphae ▪ Acts as a clearing agent EXAMINATION ▪ Lactophenol cotton blue ▪ Phenol: kills organisms ▪ Cotton blue: stains chitin & cellulose EXAMINATIONS ▪ India ink ▪ “Negative” stain ▪ Stain everything except capsule ▪ Used to diagnose cryptococcal meningitis YEAST YEAST ▪ Unicellular ▪ Reproduce by asexual fission ▪ Known as budding ▪ Colonies: ▪ Round, pasty, waxy looking YEAST ▪ 2 main genera/species: ▪ Candida spp ▪ Cryptococcus neoformans CANDIDA SPP. ▪ Most common opportunistic fungal pathogen ▪ 100+ species: ▪ C. albicans ▪ C. glabrata ▪ C. parapsilosis ▪ C. tropicalis ▪ C. krusei ▪ C. auris ▪ Resistance to fluconazole (90%), voriconazole (3-73%), amphotericin B (13-35%) CANDIDA SPP. ▪ Colonizer of: ▪ GI tract ▪ Skin ▪ Nails ▪ Vagina ▪ Urethra ▪ Oral cavity CANDIDA SPP. ▪ Pathogenesis ▪ Adherence to a variety of tissues and inanimate surfaces ▪ Yeast-to-hypha transformation ▪ Regulated by pH and/or temperature ▪ Germ tube ▪ Secreted enzymes ▪ Aspartyl proteinases hydrolyze host proteins ▪ Phospholipases damage host cells for invasion CANDIDA SPP. ▪ Thrush ▪ Yeast infection of oral cavity ▪ Thick, white patches on tongue, palate, or elsewhere ▪ May be red without white patches ▪ Painful ▪ May bleed, if wiped CANDIDA SPP. ▪ Genital ▪ Vaginal ▪ Thick, white discharge ▪ Cottage cheese appearance ▪ Itching and irritation in vagina and surrounding tissue ▪ Pain during sex or urination ▪ Penial ▪ May occur after sex ▪ Not considered STI ▪ Itching and burning of penis ▪ Skin rash CANDIDA SPP. ▪ Sepsis ▪ Occurs from gastrointestinal translocation ▪ Contaminated catheters ▪ Intravascular spread ▪ Invade deep tissues of liver, spleen, kidneys, heart, and brain CANDIDA SPP. ▪ Cutaneous rash ▪ Babies = diaper rash ▪ Adults = skin rash ▪ Armpits ▪ Skin folds ▪ Under breasts ▪ Nipple (breast feeding) CRYPTOCOCCUS SPP. ▪ 2 main species: ▪ C. neoformans ▪ C. gatti ▪ Encapsulated yeast ▪ Mainly occurs in immunocompromised hosts ▪ Host defense mainly: ▪ Alveolar macrophages ▪ Inflammatory phagocytic cells ▪ T- & B-cells CRYPTOCOCCUS SPP. ▪ Transmission ▪ Inhalation from ▪ Bird feces ▪ Soil ▪ Birds harbor Cryptococcus spp. ▪ Pigeons ▪ Canaries ▪ Parrots ▪ Cockatoos ▪ Parakeets ▪ Chickens ▪ Sparrows CRYPTOCOCCUS SPP. ▪ Host defense ▪ Alveolar macrophages ingest yeast cells ▪ Limited ability to kill ▪ Recruit neutrophils, monocytes, NK cells ▪ Complement system enhances immune response ▪ Impaired response allows disseminated infection ▪ Macrophages contain viable yeast cells ▪ Transports yeast from lung to lymphatics and blood ▪ Eventually lead to brain CRYPTOCOCCUS SPP. ▪ Pathogenesis ▪ Thick polysaccharide capsule ▪ Protects from phagocytosis and responding cytokines ▪ Suppresses cellular and humoral immunity ▪ Blocks opsonization from complement and antibodies ▪ Produces a negative charge, allowing repulsive effects from immune cells ▪ Melanin ▪ Produced via phenoloxidase enzyme ▪ Deposited on cell wall ▪ Enhances cell wall integrity ▪ Protects yeast from oxidative stress, temperature extremes, iron reduction, and microbicidal peptides CRYPTOCOCCUS SPP. ▪ Meningitis ▪ Mostly in immunocompromised patients ▪ 7-10% of AIDS patients ▪ 50% of all cases are in AIDS patients ▪ Mortality ranges: ▪ 9% to 15% in US ▪ 22% to 96% in other areas ”YEAST-LIKE” PNEUMOCYSTIS ▪ Originally classified as a protozoa ▪ DNA evidence classified it as fungus ▪ Pneumocystis carinii divided into 2 species ▪ P. carinii (rat variant, formerly human) ▪ P. jirovecii (human variant) PNEUMOCYSTIS ▪ Most seropositive between 2 to 4 years age ▪ Immunocompetent = asymptomatic infection ▪ Immunocompromised = symptomatic pneumonia ▪ AIDS ▪ Organ transplant or malignancies PNEUMOCYSTIS ▪ Symptoms ▪ Low-grade fever ▪ Non-productive cough ▪ Difficult breathing ▪ Normal chest radiographs or diffuse interstitial infiltrate PNEUMOCYSTIS ▪ Transmission ▪ Life cycle terminology = protozoan names ▪ Respiratory route ▪ Cyst = infective stage ▪ Asexual & Sexual reproduction DIMORPHIC MOLD-TO-YEAST COCCIDIOIDES C. immitis San Joaquin Valley fever C. posadasii Endemic to the Desert Southwest U.S. Northern Mexico South America COCCIDIOIDES ▪ Symptoms: ▪ Fatigue ▪ Cough ▪ Fever ▪ SOB ▪ Headache ▪ Night sweats ▪ Muscle aches ▪ Rash on upper body or legs COCCIDIOIDES ▪ Two cycles ▪ Saprophytic phase (mold) = soil ▪ Parasitic phase (yeast) = host ▪ Inhalation from soil ▪ Breaches respiratory barrier, enters blood and lymphatics, disseminates to other organs COCCIDIOIDES ▪ Pathogenesis ▪ Outer wall ▪ Prevents phagocytosis ▪ Molecular mimicry ▪ Produces protein similar structurally, antigenically, and function to host molecules ▪ Urease production ▪ Endospores phagocytosed by alveolar macrophages ▪ Viable endospores surrounded by ammonia ▪ Counteracts acidic environment in macrophages ▪ Extracellular proteinases ▪ Secreted enzymes allow invasive growth ▪ Permit ingress of skin and mucosal barriers, neutralization of host defense, transmigration of endothelial layers, and many more COCCIDIOIDES ▪ Diagnosis: ▪ EIA – Enzyme Immunoassay ▪ Culture ▪ Microscopy ▪ PCR HISTOPLASMA CAPSULATUM ▪ Disease known as: ▪ Histoplasmosis ▪ Reticuloendothelial cytomycosis ▪ Cave disease ▪ Spelunker’s disease ▪ Darling disease HISTOPLASMA CAPSULATUM ▪ Worldwide range ▪ U.S. endemicity: ▪ Ohio ▪ Missouri-Mississippi river delta ▪ Requires soil with high nitrogen content ▪ Bat and bird guano (poop) HISTOPLASMA CAPSULATUM ▪ Symptoms ▪ Fever ▪ Cough ▪ Fatigue ▪ Chills ▪ Headache ▪ Chest pain ▪ Body aches HISTOPLASMA CAPSULATUM ▪ Inhalation of microconidia ▪ Phagocytized by pulmonary macrophages ▪ Usually asymptomatic ▪ Heavy exposure = acute pulmonary disease ▪ Viable organism remain quiescent for years ▪ Immunocompromised = progressive disseminated disease HISTOPLASMA CAPSULATUM ▪ Pathogenesis ▪ pH modulation ▪ Yeast cause increase of pH in macrophages from 6.0 to 6.5 ▪ Above optimal range for lysosmal enzymes ▪ Prevents antigen processing ▪ Iron uptake ▪ Uses a siderophore to trap iron ▪ pH modulation is important for iron uptake ▪ pH >6.5 prevents iron uptake ▪ Calcium uptake ▪ Release calcium-binding protein (CBP1) into environment ▪ Prevents phagolysosome activity in macrophage HISTOPLASMA CAPSULATUM ▪ Pathogenesis ▪ Converts to yeast within hours of infection ▪ Phagocytes effective against conidia but not against yeast form ▪ Resistant towards neutrophils ▪ Macrophages can ingest but not kill HISTOPLASMA CAPSULATUM ▪ Host defense ▪ T cell-mediated immunity allows full recovery ▪ Faulty T cell immunity leads to progressive dissemination ▪ AIDS ▪ Immunosuppressive medication ▪ Malignancy HISTOPLASMA CAPSULATUM ▪ Diagnosis ▪ Antigen detection ▪ Antibody test ▪ Culture ▪ Microscopy ▪ PCR DERMATOPHYTES ▪ Trichophyton, Epidermophyton and Microsporum ▪ Keratinophilic – adapted to grow on hair, nails and skin ▪ Produce macroconidium and/or microconidium ▪ Helps with identification ▪ Cause our “tinea” infections ▪ Tinea corporis ▪ Tinea unguium ▪ Tinea capitis  DERMATOPHYTES Copyright © 2023 by Elsevier Inc. All rights reserved ASPERGILLUS ▪ Ubiquitous in the environment ▪ In culture, must determine if a pathogen or contaminant ▪ Second most commonly isolated fungus after Candida species ▪ Aspergillus fumigatus is the most commonly seen species ▪ Transmission: Inhalation ▪ Conidia are constantly inhaled ▪ Immunocompetent clear conidia ▪ Immunocompromised – mortality is high Copyright © 2023 by Elsevier Inc. All rights reserved ASPERGILLUS ▪ Diseases ▪ Allergic reactions ▪ Sensitivities to molds ▪ Fungus balls in lungs of those with constant exposure with conidia ▪ Chronic pulmonary aspergillosis seen in patients with structural damage to the lungs Copyright © 2023 by Elsevier Inc. All rights reserved ASPERGILLUS ▪ Diseases ▪ Cause disease in bone marrow transplant recipients, other transplant recipients and those with cancer ▪ Disseminated infection ▪ Starts with inhalation of conidia -> become hyphae that invade tissue and blood vessels ▪ Infections spreads hematogenously → multiorgan system involvement (brain, liver, heart and bone) Copyright © 2023 by Elsevier Inc. All rights reserved THE END