Presentation on theme: "What diseases do yeasts and molds cause?"— Presentation transcript:
1 What diseases do yeasts and molds cause? MycologyWhat diseases do yeasts and molds cause?
2 Mycology Mycology is the study of fungi which includes yeast and molds They are eukaryotic and are chemo-heterotrophs (require organic compounds for energy and a carbon source)Most have a cell wall of chitinMolds are made of long filaments called hyphaeIf there are cross walls that divide the hyphae into uninucleate units the hyphae are septate hyphaeIf there are no cross walls, the hyphae are called non-septate or coenocytic hyphaeWhen the hyphae grow and intertwine to form a mass, they are called mycelium
3 MycologyThe portion of mycelium concerned with obtaining nutrients is called the vegetative myceliumThe portion concerned with reproduction is called aerial mycelium because it usually projects above the surface of the vegetative myceliumYeasts are non-filamentous, unicellular fungi that are oval or spherical in shape.Yeasts reproduce by the process of budding
4 Mycology Dimorphic fungi When the buds fail to detach from each other, pseudohyphae are seenDimorphic fungiSome fungi, including most of the pathogenic fungi, exhibit two forms of growth. This is known as dimorphism and the organisms can grow either as a yeast-like form or a mold-like form.Frequently the form that the organism grows as is temperature dependent and at 370 C the organism grows as a yeast-like form and at RT it grows in a mold-like form. CO2 concentration or the presence of serum may also be a determining factorHow is the dimorphism of Candida albicans different from that described above?
5 Mycology How do we identify molds in the lab? Based on type of hyphae (septate versus non-septate)Based on color of myceliumBased on reproductive structuresMolds may form either sexual or asexual sporesSexual spores are formed from the fusion of nuclei from two opposite mating strains of the same species. They are only formed under special conditions, but they are used to classify fungi (more on this later)Asexual spores, which are most commonly used in identification, are formed by the aerial mycelium of a single organism by mitosis and cell division
6 ArthrosporesArthrospores are formed by the fragmentation of septate hyphae
7 MycologyChlamydospores are thick walled spores formed within a hyphae
8 MycologySporangiospores are formed within a sac (sporangium) at the end of an aerial hyphae called a sporangiophore
14 MycologyBlastospores consist of a bud coming off the parental cell
15 MycologyFungi are classified based on the type of sexual spore that they formZygomycotaHave non-septate hypheaHave asexual sporangiosporesForm sexual zygospores. They are large spores enclosed in a thick wall and formed from the fusion of two cells
17 Mycology Ascomycota Have septate hyphae Have asexual conidiospores Have sexual ascospores. Ascospores result from the fusion of nuclei of two cells. They are produced in a sac-like structure called an ascus.
21 MycologyFungal diseases – any fungal infection is called a mycosis. Mycoses are classified into five groups based on the mode of entry and the level of infective tissue:Systemic mycosis – is a fungal infection deep within the patientCan involve a number of tissues and organsUsually caused by saprophytic fungi that live in the soilThe route of transmission is via inhalation of spores. Therefore the infection usually begins in the lungs and then spreads to other tissuesThe diseases often resemble tuberculosisThe infections are not contagious
22 MycologyExamples of systemic mycoses includeCoccidioidomycosis (San Joaquin Valley Fever)– caused by Coccidiodes immitisHistoplasmosis – caused by Histoplasma capsulatumBlastomycosis – caused by Blastomyces dermatitidisSubcutaneous mycoses (mycetoma) - are fungal infections beneath the skinThey are caused by fungi that live in soil and vegetationInfection occurs when spores or hyphae are planted directly into a puncture woundThe infections are not contagiousExamples of subcutaneous mycoses includeChromomycosis – caused by Phialophora or FonsecaeMaduramycosis – caused by Allescheria boydii
24 MycologyCutaneous mycoses (ringworm) – are fungal infections of the hair, epidermis, and nailsAre caused by fungi known as dermatophytes (dermatomycosis) which secrete the enzyme keratinase which digests keratin, a protein found in hair, skin, and nails.Infection is from person to person or animal to person by contact with infected hair or epidermis.Tinea capitis is a scalp and hair infectionTinea pedis is a foot infection infection (athlete’s foot)Tinea unguium is an infection of the nailsMicrosporum, Trichophyton, and Epidermophyton are the causative agents
26 MycologySuperficial mycoses – are fungal infections localized to the hair shafts and superficial epidermal cellsIs spread by direct contact with infected hair or skinExamples areWhite piedra in which white balls are found on the hair shafts is caused by TrichosporonBlack piedra is caused by Piedra ishortaeTinea nigra in white black spots are seen on the skin is caused by Cladosporium werneckii
28 MycologyOpportunistic mycoses – caused by a pathogen that is generally harmless in its normal habitat (includes normal flora), but can become pathogenic in a debilitated or traumatized hostMucormycosis – caused by Rhizopus or Mucor in patients with ketoacidosisAspergillosis – caused after inhalation of Aspergillus spores in those with lung disease or cancerCandidiasis – caused by Candida albicans.Vulvovaginal candidiasis often occurs following antibiotic therapyThrush is an infection of the mouth and throat