Mycology Lecture Notes PDF

Pharmaceutical Microbiology and Parasitology (PHMP 211) Mycology Our Lady of Fatima University College of Pharmacy Objectives After the discussion, the students should be able to: ☐Understand the basic structures and growth of...

Pharmaceutical Microbiology and Parasitology (PHMP 211) Mycology Our Lady of Fatima University College of Pharmacy Objectives After the discussion, the students should be able to: ☐Understand the basic structures and growth of fungi ☐Learn the pathogenesis of the organisms ☐Identify the different types of fungal infection based on their affectation and pathogenesis ☐Identify the different laboratory tests and diagnostic prodecures for fungal infection ☐Learn the different Pharmacologic therapies against fungal infections. Introduction Mycology ☐ is the branch of biology that deals with the study of fungi, including their genetic and biochemical properties, their taxonomy as well as pathogenesis and toxicity Fungi ☐Eukaryotic microorganisms that occur ubiquitously in nature in the domain Eucarya. The kingdom fungi (Mycota) has over 50,000 different species but only 200 have been identified as human pathogens. Comparison of Fungi and Bacteria Fungal Cell wall: ☐Chitin: a polysaccharide composed of long chains of N- acetylglucosmine and plenty of polysaccharides such as β- glucan ☐β- glucan: a long polymer of D- glucose ☐ Medically important ( site of echinocandin action) Fungal Cell membrane: ☐Ergosterol ( the alternative in human cholesterol) ☐Site of action of Ampothericin B and Azoles Two types of Fungi ❑Yeast: A single cell that reproduce through budding ❑Molds: Grow as long filaments ( hyphae) and form a mat (mycelium) ❑Some hyphae for Transverse walls (septate hyphae); others do not (nonseptate hyphae) Morphology The taxonomy of the fungi is essentially based on their morphology. ☐Classifications: ☐Dermatophytes: ☐ causes infection of the keratinized tissues ☐Yeast: ☐ single cells ☐Molds: ☐ grow in filamentous structures ☐Dimorphic fungi: ☐They exist as molds in the environment at ambient temperature and as yeasts (or other structures) in human tissues at body temperature  Morphology ☐Hypha: this is the basic element of filamentous fungi with a branched, tubular structure, 2–10 lm in width. ☐Mycelium: this is the web or matlike structure of hyphae. ☐Substrate mycelia (specialized for nutrition) penetrate into the nutrient substrate. ☐Aerial mycelia (for asexual propagation) develop above the nutrient medium. ❑Fungal thallus: this is the entirety of the mycelia and is also called the fungal body or colony ❑Yeast: the basic element of the unicellular fungi. It is round to oval and 3– 10 micrometer in diameter. Several elongated yeast cells chained together and resembling true hyphae are called pseudohyphae ❑Dimorphism: some fungal species can develop either the yeast or the mycelium form depending on the environmental conditions, a property called dimorphism. ☐ Dimorphic pathogenic fungi take the form of yeast cells in the parasitic stage and appear as mycelia in the saprophytic stage Metabolism All fungi are carbon heterotrophs: ☐Dependent on exogenous nutrient substrates as sources of organic carbon, and with a few exceptions, fungi are obligate aerobes. ☐None are obligate anaerobes Known Metabolic Types: ☐Thermophilic ☐Psychrophilic ☐Acidophilic ☐Halophilic Reproduction: Sexual reproduction: ☐They reproduce sexually by mating and forming sexual spores ☐Zygospores: Single large spore with thick walls ☐Ascospores: Formed in a sac called ascus ☐Basidiospores: Formed externally on the tip of the pedestal called basidium Some Important Conidia Asexual reproduction: ☐Formation of conidia (asexual spores) from the sides or the ends of specialized structures ☐A. Arthrospore: arises by fragmentation of the ends of the hyphae( mode of transmission of Coccidiodes immitis) ☐B. Chlamydospore: rounded, thick-walled and quite resistant. A. Arthrospore B. Chlamydospore ☐C. Blastospores: formed by budding process of yeast ☐Some yeast ( C. albicans, can form C. Blastospores multiple buds that do not detach, thus producing sausage-like chains called pseudohyphae ☐D. Sporangiospores: formed within a sac (sporangium) on a stalk by molds such as Rhizopus and Mucor D. Sporangiospores Important Fungal Diseases Medical Mycoses according to site of infection: ☐Superficial mycoses ☐Cutaneous mycoses ☐Subcutaneous mycoses ☐Deep Mycoses ☐Systemic mycoses: ☐ Fungi that are able to cause systemic infection ☐Primarily involve the respiratory system ☐Opportunistic mycoses: ☐Systemic infection caused by normal flora that become opportunistic in immunocompromised patients Superficial Mycoses These are limited to the stratum corneum and essentially elicit no inflammation. ☐1. Pityriasis versicolor is a common superficial mycosis, which is characterized by hypopigmentation or hyperpigmentation of skin of the neck, shoulders, chest, and back. ☐Pityriasis versicolor is due to Malassezia furfur, Malassezia globosa, Malassezia restricta, which involves only the superficial keratin layer.  Superficial Mycoses ❑ 2. Black piedra is a superficial mycosis due to Piedraia hortae which is manifested by a small firm black nodule involving the hair shaft. Superficial Mycoses ❑ 3. White piedra due to Trichosporon beigelii is characterized by a larger, softer and yellowish nodules on hair Superficial Mycoses 4. Tinea nigra most typically presents as a brown to black silver nitrate-like stain on the palm of the hand or sole of the foot and and is caused by Hortaea werneckii. Cutaneous Mycoses 1. Dermatophytoses: ☐caused by fungi (dermatophytes) that infect only superficial keratinized structures (skin, hair, and nails), not deeper tissues. ☐Three important genera: ☐Microsporum: Infects hair and skin but not the nails ☐Trichophyton: Infects hair, skin and nails ☐Epidermophyton: Infects skin and nails but not the hair 2. Dermatomycoses: ☐cutaneous infections due to other fungi, the most common of which are Candida spp  Dermatophytes ☐Tinea pedis: affects the feet ☐Athelete’s foot ☐Tinea unguium: affects the fingernails and toenails ☐Onchomycosis ☐Tinea corporis: affects the arms limbs and trunk ☐Ring worm ☐Tinea cruris: affects the groin area ☐Jock itch ☐Tinea manuum: affects the hand and palm area worse than tinea pedis ☐Tinea capitis: affects the scalp ☐Tinea barbae: affects the facial hair ☐Barber’s itch ☐Tinea faciei: affects the face ☐Face fungus Subcutaneous Mycoses ☐These include a range of different infections characterized by infection of the subcutaneous tissues usually at the point of traumatic inoculation ☐An inflammatory response develops in the subcutaneous tissue frequently with extension into the epidermis. Subcutaneous Mycoses Three general types: ☐Chromoblastomycosis ☐Mycetoma ☐Sporothricosis Subcutaneous Mycoses: Chromoblastomycosis  Subcutaneous mycosis characterized by verrucoid lesions of the skin (usually of the lower extremities);  Histological examination reveals muriform cells (with perpendicular septations) or so-called "copper pennies" that are characteristic of this infection. Copper pennies Subcutaneous Mycoses: Chromoblastomycosis ▪ Generally limited to the subcutaneous tissue with no involvement of bone, tendon, or muscle. ☐The most common causes of chromoblastomycosis: ☐Fonsecaea pedrosoi ☐ Pedroso’s disease ☐Fonsecaea compacta ☐ Fonseca’s disease ☐Cladophialophora carrionii, ☐ Cladosporiosis ☐Rhinocladeiella aquaspersa ☐Phialophora verrucosa. Subcutaneous Mycoses: Mycetoma A suppurative and granulomatous subcutaneous mycosis, which is destructive of contiguous bone, tendon, and skeletal muscle. Mycetoma is characterized by the presence of draining sinus tracts from which small but grossly visible pigmented grains or granules are extruded. Subcutaneous Mycoses: Mycetoma ☐The causes of mycetoma are more diverse but can be classified as eumycotic and actinomycotic mycetoma. ☐The most common agent: ☐ Eumycotic mycetoma Pseudallescheria boydii ☐Actinomycotic mycetoma Nocardia brasiliensis. Madura foot Subcutaneous Mycoses: Mycetoma Figure: Madura foot or Mycetoma: Foot disfigured by the destructive nature of mycetoma due to delay in instituting clinical management Subcutaneous Mycoses: Mycetoma Fungi causing mycetoma: Dematiaceous (melanized) Fungi  Pigmented brown to black.  The melanin pigment is deposited in the cell walls of these organisms.  These fungi may produce a range of infections from superficial to subcutaneous to deep (visceral) infection characterized by the presence of dematiaceous hyphal and/or yeast-like cells in tissue.  Such deep infections due to dematiaceous fungi are termed phaeohyphomycosis. Subcutaneous Mycoses: Sporotrichosis ☐This infection is due to Sporothrix schenckii and involves the subcutaneous tissue at the point of traumatic inoculation. ☐The infection usually spreads along cutaneous lymphatic channels of the extremity involved.  Deep Mycoses: Systemic Mycoses 1. The primary pathogenic fungi are A able to establish infection in a normal host  The primary deep pathogens usually gain access to the host B via the respiratory tract.  The primary systemic fungal pathogens include  A. Coccidioides immitis C  B. Histoplasma capsulatum  C. Blastomyces D dermatitidis  D. Paracoccidioides brasiliensis. Deep Primary Mycoses: Coccidioidomycosis  Known as the “Valley Fever”  The arthrococonidia of Coccidioides immitis are inhaled and convert in the lung to spherules.  Most cases of are clinically occult or mild infections in patients who inhale infective arthroconidia.  Some patients have progressive pulmonary infection and also may suffer dissemination to the brain, bone, and other sites.  Coccidioides meningitis is a life-threatening infection requiring lifelong treatment.  Deep Primary Mycoses: Histoplasmosis  A primary pulmonary infection resulting from inhalation of conidia of Histoplasma capsulatum which convert in vivo into the blastoconidial (budding yeast) form.  Dissemination to the hilar and mediastinal lymph nodes, spleen, liver, bone marrow, and brain may be life-threatening in infants and other immunocompromised patients. Common in AIDS  Histoplasmosis (like tuberculosis) is characterized by intracellular growth of the pathogen in macrophages and a granulomatous reaction in tissue.  Deep Primary Mycoses: Histoplasmosis ☐Histoplasmosis also may be associated with a chronic inflammatory process known as fibrosing mediastinitis, where scar tissue (formed in response to H. capsulatum) encroaches on vital structures in the mediastinum (mid chest area) Autopsy specimens of the right lung from patient with fibrosing mediastinitis after histoplasmosis. Note the narrowing of artery (red arrow) and vein (white arrow) Deep Primary Mycoses: Blastomycosis  Similar to histoplasmosis, is a primary pulmonary infection resulting from inhalation of conidia from the mycelial phase of Blastomyces dermatitidis which convert in vivo to the parasitic yeast phase. In the blastoconidial phase also causes a primary pulmonary infection. This may cause chronic pneumonia  The organism elicits a granulomatous reaction often associated with a marked fibrotic reaction.  Disseminated Blastomycosis: spread of the fungi to the skin, bones and prostate in male  Deep Primary Mycoses: Paracoccidiodes ☐Paracoccidioides brasiliensis causes paracoccidioidomycosis ☐also known as South American blastomycosis. a dimorphic fungus that exists as a mold in soil and as a yeast in tissue. The yeast is thick-walled with multiple buds, in contrast to B. dermatitidis, has a single bud ☐This fungus grows in the soil and Paracoccidioides: is endemic in rural Latin America. yeasts with multiple buds resembling a “ship captain’s wheel.” Disease occurs only in that Stain: Methenamine silver stain region. Deep Opportunistic Mycoses Opportunistic fungi causing deep mycosis invade via the respiratory tract, alimentary tract, or intravascular devices.  Opportunistic pathogens require a compromised host in order to establish infection (e.g., cancer, organ transplantation, surgery, and AIDS). Oral candidiasis in  The opportunistic fungal immunocompromised patient pathogens include:  Cryptococcus neoformans  Candida spp.  Aspergillus spp.  Penicillium marneffei  the Zygomycetes  Trichosporon beigelii  Fusarium oxysporum Oral candidiasis in new born Deep Opportunistic Mycoses: Candidiasis ❑ Candidiasis (due to C albicans and other Candida spp.) is the most common opportunistic fungal infection. Candida albicans is the most common cause of candidiasis. A. Superficial candidiasis ❑ may involve the epidermal and mucosal surfaces, including those of the oral cavity, pharynx, esophagus, intestines, urinary bladder, and vagina B. Deep (or visceral) candidiasis. ❑ The alimentary tract and intravascular catheters are the major portals of entry ❑ The kidneys, liver, spleen, brain, eyes, heart, and other tissues are the major organ sites involved in deep or visceral candidiasis. ❑ The principal risk factors predisposing to deeply invasive candidiasis are protracted courses of broad spectrum antibiotics, cytotoxic chemotherapy, corticosteroids, and vascular catheters. Deep Opportunistic Mycoses: Candidiasis Interdigital candidiasis Cutaneous candidiasis Nappy rash in infant that spreads in the mouth Diaper candidiasis that resembles tinea Deep Opportunistic Mycoses: Aspergillosis Invasive aspergillosis most frequently involves the lungs and paranasal sinuses. The fungus, Aspergillus fumigatus may disseminate from the lungs to involve the brain, kidneys, liver, heart, and bones. The main portal of entry for aspergillosis is the respiratory tract, however, injuries to the skin may also introduce the organism into susceptible hosts. Deep Opportunistic Mycoses: Zygomycosis  Zygomycosis due to Rhizopus, Rhizomucor, Absidia, Mucor species, or other members of the class of Zygomycetes, also causes invasive Sinopulmonary infections.  An especially life-threatening form of zygomycosis (also known as Mucormycosis), is known as the rhinocerebral Periorbital mucormycosis syndrome, which occurs in diabetics with ketoacidosis, this disease is highly lethal Deep Opportunistic Mycoses: Cryptococcosis  Cryptococcosis is an encapsulated yeast that is most typically an opportunistic fungal infection that most frequently causes pneumonia and/or meningitis.  Defective cellular immunity, especially that associated with the acquired Immune deficiency syndrome, is the most common risk factor for Developing cryptococcosis.  It is caused by Cryptococcus neoformans Deep Opportunistic Mycoses: Phaeohyphomycosis ❑Phaeohyphomycosis is an infection by brown to black pigmented fungi of the cutaneous, superficial, and deep tissues, especially brain. ❑These infections are uncommon, life-threatening, and occur in various immunocompromised states. Deep Opportunistic Mycoses: Hyalohyphomycosis Hyalohyphomycosis is an opportunistic fungal infection caused by any of a variety of normally saprophytic fungi with hyaline hyphal elements. ❑ fungal agent with septate hyphae and nonpigmented (hyaline) ☐Traditionally, the disseminated and corneal forms of hyalohyphomycosis have been most commonly identified Fungal keratitis due to Acremonium strictum. Fig A: initial assessment, Fig B: six months after therapy Dimorphic mycoses Dimorphism in the Pathogenic Fungi  Fungal dimorphism is the morphological and physiological conversion of certain fungi from one phenotype to another when such fungi change from one environment to another.  Dimorphic fungi include C immitis, H capsulatum, B dermatitidis, P brasiliensis, P marneffei, and S schenckii, and certain opportunistic fungi such as Candida albicans and Penicillium marneffei.  Various environmental host factors control fungal dimorphism. These factors include amino acids, temperature, carbohydrates, and trace elements (e.g. zinc). Dimorphic fungi Dimorphic fungi 1. S. schenckii, the morphological transformation is from a hyphal form to a yeast-like form (or spherule in the case of C immitis) in tissue 2.the dimorphism of Candida albicans is somewhat different in that the organism transforms from a budding yeast-like structures (blastoconidia) to filamentous structures known as germ tubes. Other filamentous structures may later develop as pseudohyphae and hyphae. Dimorphic Fungi 3. Penicillium marneffei is unique in being the only Penicillium species pathogenic to humans. It undergoes dimorphic conversion in vivo to transversely dividing sausage- shaped cells. Diagnosis and Laboratory Examinations Tests for superficial infection: ☐KOH prep ( potassium hydroxide solution) ☐Sample: Skin scrapings, hair or nail clippings, tissue, vaginal swab, body fluids, sputum ☐Description: Reveals yeast cells and fungal hyphae (branching filaments) ☐Use: Primary screening tool, detects fungi but does not tell what specific fungus is present ☐Time of result: Rapid Diagnosis and Laboratory Examinations Tests for superficial infection: ☐Calcofluor white stain ☐Sample: Skin scrapings, hair or nail clippings, tissue, vaginal swab, body fluids, sputum ☐Description: Stain binds to fungal elements in a sample and fluoresces ( glows) under UV light. ☐Use: Detects fungi but does not tell what specific fungus is present ☐Time of result: Rapid Diagnosis and Laboratory Examinations Tests for superficial infection: ☐Fungal Culture ☐Sample: Skin scrapings, hair or nail clippings, tissue, vaginal swab, body fluids, sputum ☐Description: Sample is placed on or into a culture media and incubated to grow. ( Sabouraud dextrose agar) ☐Use: Primary tool to diagnose a fungal infections, grows fungi for identification and susceptibility test ☐Time of result: Weeks Diagnosis and Laboratory Examinations Tests for Systemic infection: ☐Susceptibility Testing ☐Sample: Sample of fungus isolated in culture ☐Description: Follow up to fungal culture, when a pathogenic culture has been identified, this is done to know the best medication against the fungi ☐Use: Guide treatment ☐Time of result: Days to weeks after culture Diagnosis and Laboratory Examinations Tests for Systemic infection: ☐Antigen Testing ☐Sample: Blood, urine, CSF and body fluids ☐Description: Detects proteins associated with a specific fungus ☐Use: Diagnose infection by specific fungus ☐Time of result: Days; rapid test are available for some fungi ( Cryptococcus, Histoplasma spp.) Diagnosis and Laboratory Examinations Tests for Systemic infection: ☐Antibody Testing ☐Sample: Blood, urine, CSF and body fluids ☐Description: Detects immune response to a specific fungus ☐Use: Diagnose current or recent infection by specific fungus; monitor treatment ☐Time of result: Days to weeks Diagnosis and Laboratory Examinations Tests for Systemic infection: ☐Molecular test for DNA and RNA ☐Sample: Sample of fungus isolated in culture, blood, CSF and body fluids ☐Description: Detects genetic material from specific fungus ☐Use: Detects some fungi, not widely available, some in research setting only ☐Time of result: Days to weeks Treatment of Fungal infection Treatment of Fungal infection Polyene macrolide: ☐Ampothericin B ☐MOA: Forms pores in fungal membranes (which contain ergosterol) but not in mammalian (cholesterol containing) membranes ☐Effect: Loss of intracellular contents through pores is fungicidal ; broad spectrum of action ☐Clinical Application: Localized and systemic candidemia; Cryptococcus; Histoplasma; Blastomyces; Coccidioides; Aspergillus ☐Kinetics: Oral form is not absorbed, IV for systemic use ☐Toxicity: Infusion reaction, Renal impairment Treatment of Fungal infection Pyrimidine Analog ☐Flucytosine ☐MOA: interferes with the DNA and RNA synthesis selectively in fungi ☐Effects: Synergistic effect with amphotericin; systemic toxicity in the host DNA and RNA effects ☐Clinical applications: Cryptococcus and Chromoblastomycosis infection ☐Kinetics: Oral, renally excreted ☐Toxicity: Myelosuppression Treatment of Fungal infection ☐Azoles ☐Ketoconazole ☐ MOA: Block fungal P450 enzymes and interfere with ergosterol synthesis ☐Effects: Poorly selective, interferes with P450 mammalian function ☐Clinical Application: Broad spectrum but toxicity restricts use to topical therapy ☐Kinetics: Oral, topical ☐Toxicity: Interferes with steroid hormone synthesis and Phase I drug metabolism Treatment of Fungal infection ☐Azole ☐Itraconazole ☐MOA:Block fungal P450 enzymes and interfere with ergosterol synthesis ☐Effects: Much more selective than ketoconazole ☐Clinical Application: Broad spectrum: Candida, Cryptococcus, blastomycosis, coccidiodomycosis, histoplasmosis ☐Kinetics: Oral and IV, 1-2 days, poor CNS penetration ☐Toxicity: Low toxicity Same actions: Fluconazole, voriconazole, posaconazole, isavuconazole: Fluconazole has excellent CNS penetration, used in fungal meningitis Treatment of Fungal infection ☐Echinocandins ☐Caspofungin ☐MOA: Blocks beta glucan synthase ☐Effects: Prevents synthesis of fungal cell wall ☐Clinical Application: Fungicidal Candida spp. Also used in aspergillosis ☐Kinetics: IV only, 11-15 hour duration ☐Toxicity: Minor GI effects, flushing ☐Interaction: Increase cyclosporine level (avoid combination) Micafungin, anidulafungin: Micafungin increases levels of nifedipine, cyclosporine, sirolimus; anidulafungin is relatively free of this interaction Treatment of Fungal infection ☐Allylamine ☐Terbinafine ☐ MOA: Inhibits epoxidation of squalene in fungi, increased levels are toxic to fungi ☐Effects: Reduces ergosterol, prevents synthesis of fungal cell membrane ☐Clinical Application: mucocutaneous infections ☐Kinetics: Oral, duration: days, ☐Toxicity: GI upset, headache, hepatotoxicity