Eukaryotic microbes

IMED2000

• eukaryotic

• important environmental organisms

• Most are harmless to humans

• are commensal organisms, used in biotechnology: wine, beer, soy sauce, bread production

• commonly cause skin and hair infections

• More serious opportunistic infections in immunocompromised individuals

funghi

• eukaryotes - (true nucleus)

• funghi

• protoza

• helminths

• other infectious agents - prions

microbes

• filamentous - made up of microscopic filaments called hyphae

• hyphae form a branched structure – mycelium (mold colony)

• Multicellular/multinucleate

Mould - type of funghi structure 1

• Filamentous forms grow by extension of the ends of the hyphae (roots) and production of spores (conidia)

• Sporulation on aerial hyphae - many different structural forms

• Spores are important for dispersal and easily carried by wind dormant survival structure - resistant to heat, chemicals, standard autoclaving (sterilisation to kill bacteria)

• Yeasts can grow - budding or binary fission

fungal growth and reproduction

• cell wall has unique composition

• Ergosterol – cell membrane, (Not found in mammalian cell membrane) Target for antifungals

• Chitin (polysaccharide) found on exoskeleton of arthropods, target for antifungals

• B-glucan – cellulose - Cross-linked and provide rigidity to wall

fungi wall structure

• Single celled animals

• Most protozoa are harmless

• Do not have a cell well – a few have a structure called a pellicle which provides similar protection

• Many protozoa are capable of movement

• can contain use cilia use pseudopodia use flagella

Protozoa

• Trophozoite - Motile, feeding and dividing stage

• Cyst - Non-motile, dormant, survival stage, Usually the infective stage

protozoa life cycle

• transmission is most common from food/water contamination or insect vectors

• pathogens have various strategies including intracellular and extracellular modes

• have evolved various strategies to survive immune responses

• symptoms of protozoan infections - due to immune reactions

protozoan sites of infection

• large adult form

• some life cycle stages are microscopic

• parasitic worms

helminths

• ingesting an host (animal) which has the larvae in tissue

• Faecal-oral route - ingesting eggs or larvae from faeces of host

• Skin penetration - larvae is able to penetrate the skin

• Tapeworms feed by absorption of the intestinal contents

• blood sucking insect - larvae develop in the insect of intermediate host and inject it into circulatory system

• e,g. tapeworms, roundworms, flukes

transmission of helminths

• release of eggs from urine or faeces

• hatching of eggs

• infect an intermediate host

• host produces a larvae which can penetrate skin

helminths life cycle

• Acellular infectious agents – none genetic material

• abnormally folded protein

• Causes spongiform encephalopathies (damage CNS)

• forms large vacuoles in the CNS, effects personality, depression, lack of coordination and unsteady gait

• Very resistant to disinfection and sterilisation methods

• formaldehyde protects the protein in the brain for decades can be infectious

• Disease is very slow in progression – decades

• No defence or cure - essentially no immune response

prions

• The abnormal prion protein binds to the normal prion protein in the intercellular space and causes it to mis-fold.

• The accumulation of misfolded proteins forms a plaque which disrupts cell function causing damage to tissue.

• genetic

how prions damage cells

• ingestion of contaminated foods

• Contamination of medical equipment and medical products has also been described

• Cross-species transmission is possible, but not to humans except from cattle

• Currently no treatment

transmission of prions

• Yeasts – single celled (unicellular), usually larger than bacteria, oval shaped

yeast - funghi structure 2

• when a species is both filamentous (mould) and unicellular growth (yeast)

• depends on temperature

• room temp - filamentous

• body temp - unicellular

dimorphic structure

• Superficial (hair shaft, dead layer of skin cells)

• Cutaneous (epidermis, hair, nail)

• Subcutaneous (dermis, subcutis)

• Systemic (internal organs)

• opportunistic (internal organs)

fungal disease and anatomical sites