Mycology, Virology & Parasitology
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How do yeasts differ from moulds?
• Moulds: mycelial growth made of branching tubular filaments called hyphae • True yeasts: unicellular
What is a dimorphic fungus?
• A fungi that can exist either as a mould or a yeast
What media is used for growing fungi?
• Sabouraud’s agar
Why are oranges spoilt by mould rather than bacteria?
• The environment of an orange suits the growth of fungi rather than bacteria (it is acidic, moderate temp, aerobic, moist)
Types of asexual spores of fungi
• Sporangiospores • Chlamydospores (spores within thickened cell wall of hyphae) • Conidiospores (naked spores in chains at hyphal tip) • Arthrospores (fragmentation of hyphae) • Blastospores (form as buds)
Four stages of fungal sexual spore formation
• Cells of + thallus and – thallus fuse (Dikaryotic stage) • After several hours / years/ centuries nuclei fuse (diploid stage) • Meiosis of nucleus restores haploid state • Haploid nucleus partitioned into + and - spores
Three types of fungal sexual spores.
• Zygospores • Basidiospores • Ascospores
Dermatophyte that causes tinea
• M. gypseum or T. mentagrophytes
Sporotrichosis is caused by which fungus?
• Sporothrix schenckii
Systematic mycoses are caused by which fungi?
• Histoplasmosis (H. capsulatum) • Blastomycosis (B. dermatitidis) • Coccidiodomycosis (Coccidioides immitis) • Paracoccidoidomycosis (Paracoccidioides brasiliensis)
Candidosis, crytococcosis and pneumosystis pneumonia are diseases caused by opportunistic fungi. True or false?
True
Mycotoxins contaminate approximately 25% of foods world wide, however usually do not cause disease, why?
• They only rarely appear at a dangerous level
Why can’t viruses by grown on artificial media?
• Viruses cannot live by themselves, they require a host cell to reproduce themselves
What is the main feature of viruses that is used to classify them?
• Whether they contain DNA or RNA (enveloped or non enveloped)
What two main viral symmetries do viruses causing human diseases have?
• Most human viral infections are caused by viruses that have iscosahedral or helical symmetries
What two ways that viruses can cause disease?
• Replication within the host cell leading to direct damage of the cell • Host defenses leads to cell damage as it attempt to clear the virus infected cells
Stages of viral infectivity
• Attachment (to host cell via specific receptor on cell membrane) • Penetration (entry into host cell, uncoating protein shell) • Replication of viral genome • Production of late viral proteins (structural) • Assembly of the progeny virions • Release of virions from cell (budding or lysis)
Two methods of viral control
• Heat - Disinfectants
What is the basic structure of viruses?
• Nucleic acid core (DNA or RNA) - Capsid (capsomeres)
Two modes of transmission of viruses
• Physical contact - Food borne
Two methods of detecting viruses for diagnostic purposes
• Fluorescent microscopy - Serological tests (blood samples)
Prion
• A proteinaceous infectious particle
Names for round and flat worms
• Nematodes (round) - Platyhelminths (flat)
Trichinella spiralis is found in what type of food?
• Pig meat