MMI 133

Important as nosocomial (hospital acquired) infections and as opportunistic infections of immunocompromised, few are primary pathogens

• Decomposition of plant matter
• edible mushrooms
• leavening agent for bread, fermentation for beer, wine, etc.

• Cells walls of fungi have ergosterol in cell membrane (unlike the cholesterol that we have)
• Many antifungal drugs affect ergosterol synthesis;
• Amphotericin B
• Azoles
• Nystatin

• 1. Moulds
• 2. Yeasts
• 3. Dimorphic

Have caenocytic and septate types (divisions between cells, or none)

• Oval or spherical
• reproduce by budding (bud eventually breaks off)
• If buds fail to detach may form pseudohyphae
• Candida albicans may attach to epithelial cells as a yeast, but invades deeper tissues by means of psuedohyphae
• Saccharamyces - yeast-ethanol for wine; carbon dioxide for leavening bread dough
• Yeasts are capable of facultative anaerobic growth, most moulds are aerobic growth only. (important for invasiveness)
• Some yeasts produce a polysaccharide capsule eg Cryptococcus neaformans

• Two forms of growth, can grow as a mould or a yeast, temperature dependent
• Dimorphism: pathogenic species grow as moulds at lower temperatures and yeast at body temperatures.
• eg Histoplasma capsulatum is a yeast in the body at temp <35C is a mould
• Dimorphic fungi are not infectious from one person to another - the mould form is spread by spores in air

• Also called "Rose Gardener's Disease"
• Fungal spores introduced into wound
• Lymphangitis common (usually are or leg) - causes more ulcers as disease progresses

• Fungal spores are for reproduction (not survival)
• Spores are important for identification
• Fungal spores are very different from bacterial spores

• Less nutritionally demanding than bacteria
• Grow better than bacteria in extreme conditions
• Most are aerobic
• Most grow best at 25-30C

• All fungal diseases are called: mycoses
• Singular: mycosis
• 3 types of mycoses: 1 Superficial, 2 Cutaneous, 3 Systemic (3 is more severe, 1 least severe)

• fungal infection along surface of hair shafts and outer layer of skin
• mild infections
• -black and white piedra (hairs of scalp)
• -Malassezia furfur (a yeast)

• fungal infection of deeper layers of the epidermis by moulds (eg. athletes foot or ringworm)
• caused by dermatophytes (degrade keratin)
• -few different moulds, same mechanism of pathogenicity
• clinical diseases are called "tineas" (eg. tinea capitis involves head; tinea pedis feet; tinea cruris groin; tinea corporis torso; tinea barbae beard; etc)

• Infections in deep tissues (organs)
• -either caused by primary pathogens such as Histoplasma capsulatum, Coccidioides immitis, Penicillium marneffei
• -or opportunistic pathogens such as Canadida albicans

• Common cause of infections in immunocompromised individuals (eg. Aspergilosis; caused by Aspergillus niger; infects people with debilitating lunch diseases,
• immunocompromised

• *Canadida albicans
• causes vulvo-vaginal candidiasis and thrush (occurs in newborns, immunocompromised and in people who have been treated with "broad spectrum" anitibiotics
• *Normal flora in gut and mouth

• Protozoa - one-celled eukaryotes
• Metazoa or Helminths - multicellular eukaryotes
• Ectoparasites

• Most reproduce asexually by fission, budding or schizogony (multiple divisions of nucleus and cell)
• Some reproduce sexually and have gametes (haploid sex cells) eg. Plasmodium species
• Some have cyst form, protection from inhospitable environments - growing form called "trophozoite"
• Cyst form may also be called an oocyst in some types of protozoa. e.g. Cryptosporidium species

• 1. Entamoeba histolytica
• 2. Giardia lamblia
• 3. Trichomonas vaginalis
• 4. Acanthamoeba
• 5. Cryptosporidium
• 6. Toxoplasma gondii
• 7. Trypanosoma
• 8. Leishmania
• 9. Plasmodium