Infectious Agents Flashcards
What are the 4 biological groups of microbes?
- viruses
- bacteria
- fungi
- parasites (protozoa, helminths)
What are key features of viruses?
- 20nm to 300nm
- DNA OR RNA core in protein capsid + capsomeres
- helical, cubic or more complex
- no cytoplasm
- envelope (derived from host cell)
What are common viral infections in the UK?
Community:
- upper resp tract infection - rhinovirus, influenza, RSV
- gastroenteritis eg. Norovirus, rotavirus, adenovirus
HC-associated infection:
- norovirus
What are key features of bacteria?
- 0.5 μm to 3 μm
- prokaryotic
- haploid DNA
- no nucleus or mitochondria
- rigid cell wall (peptidoglycan)
What are some important differences between prokaryotic and eukaryotic cells?
Prokaryotes vs eukaryotes
- 1 vs many chromosome
- no nuclear membrane vs nuclear membrane
- no mitochondria vs mitochondria
- no sterols vs sterols
- 70s vs 80s ribosomes
- no introns vs introns
What are differences between bacterial gram-positive and gram-negative cell walls?
Gram positive = thick peptidoglycan layer
- no outer membrane
- stain blue/purple
Gram negative = thin peptidoglycan layer
- no teichoic acids traversing wall
- lots of lipids + lipoproteins
- stain red
How do bacteria grow?
By binary fission, doubling time takes 20-30 mins
What conditions does bacterial growth require?
- carbon, water, nitrogen
- nutrients + minerals
- correct pH, osmotic pressure, temp (35-37C), atmosphere
What are common bacterial infections in the UK?
Community:
- UTI - E.coli
- Pharyngitis - streptococcus pyogenes
HC-associated infection:
- Post op - staphylococcus aureus -> MRSA
- vent-associated pneumonia (on ITU) - pseudomonas aeruginosa
Describe key features of fungi
- over 2μm
- eukaryotic
- haploid or diploid DNA
- single or multiple nuclei
- rigid chitinous cell wall
- multicellular or dimorphic sometimes
What is the difference between a teleomorph and anamorph?
teleomorph - sexual
anamorph - asexual
What is mycoses and examples?
Mycosis is a fungal infection in animals
- superficial mycoses (mucous membranes eg. ringworm or thrush)
- subcutaneous mycoses (mycetoma)
- systemic mycoses (histoplasmosis)
What are some key features of parasites?
eukaryotic
- protozoa: eg. plasmodium sp - malaria
- -> single cell, 5-300μm, haploid
- helminths: eg. cestode/tapeworm, trematoda, nermatodes
- -> parasitic worms, multicellular, visible to naked eye
Which microbe group cannot be visualised by light microscopy?
Viruses - require EM x40,000
What are the two main morphologies of bacteria?
Cocci - spherical
bacilli/rods - cylindrical
