Pathogens Flashcards
Give an example of the binomial classification
Escherichia coli
Recall the Linnaean classification system
Domain Kingdom Phylum Class Order Family Genius Species Strain Isolate
Describe viruses: size, genome size
most are 20 nm to 300 nm
• genome size 9Kb- 300Kb
Describe the structure of viruses
DNA or RNA genome linear, segmented, single or double stranded
- protein nucleocapsid - individual capsomeres. Helical, cubic, or complex arrangement
- Enveloped or non-enveloped may have components derived from host cell
- No cytoplasm
What is the difference between non-enveloped and enveloped viruses?
Non-enveloped is much more robust and survive on viruses
Membraned once are easily degraded
Common viral infections in the UK community…
- Upper respiratory tract infection - rhinovirus, influenza, RSV
- Gastroenteritis e.g. Norovirus (SRSV), adenovirus(non-enveloped virus), rotavirus
- Rashes e.g. varicella zoster virus (chickenpox), measles
- Meningitis e.g. enterovirus, bacteria meningitis is lethal
- Hepatitis virus e.g. HepB
- Human Papilloma virus (HPV) - genital warts
Healthcare-associated Infections (Hospital Acquired)…
• Norovirus, flu
• Influenza
Surface haemagglutinin allow it to adhere to cells and form component vaccines against flu. Eg Influenza
What virus causes these muco-cutaneous lesions?
- Human Herpes simplex Type 1
* Chicken pox virus is herpes virus with similar shape
Describe the structure of bacteria
- Size: 0.5 μm to 3 μm
- Structure: Prokaryotic. Haploid DNA, circular genome. no nucleus
- usually have rigid cell wall made of peptidoglycan of sugars outside cytoplasmic membrane
- some bacteria have capsules of polysaccharide that block antibody binding and other pathogens
- Fimbria(pilli) allow bacteria to attach to surfaces.
- Polar flagella on bacteria is on one side and allow it to migrate
- no mitochondria.
What is the difference in staining of gram negative and positive bacteria?
gram positive- dark purple
Gram negative: pink
What was the 1st influenza to be sequenced?
Haemophilus influenze
Describe fungi
- Size: over 2 μm
- Structure: Eukaryotic. Haploid or diploid DNA
- Single or multiple nuclei
Describe the cell wall structure of fungi
• Rigid chitinous cell wall outside cytoplasm
What is the filamentous form of fungi?
- Filamentous form/moulds. – hyphae (e.g. Aspergillus spp) multinucleate branching hyphae forming mycelium
What is classification of fungi based on?
morphology (growth form),
- mode of reproduction (sexual or asexual)
- disease caused: 70,0000species ~300 human pathogens
What are the types of infection caused by fungi? Give examples of each. (3)
- Superficial mycoses: Skin, nail hair and mucous membranes (dermatophytes) or thrush (Candida albicans)
- Cutaneous - e.g. Tanea – aka ringworm
- Systemic mycoses: e.g Histoplasmosis. Histoplasma capsulatum pores that can be breathed in
What is oral candidiasis?(3)
- most common oral fungal infection
- carriage rates 20% - 75% without any symptoms.
- Usually Candida albicans
Describe yeast infections (3)
- normal constituent of the digestive and vaginal tracts
- Generally, no problems in healthy people
- Opportunistic pathogens
Describe opportunistic infections in AIDS(3)
• (Previously classified as a protozoan)
o PCP(Pneumocystis pneumonia) in AIDS
o Single cells
o forms cysts containing sporescapsule
What can Cryptococcus neoformans cause in AIDS?
Fungal yeast like form – encapsulated – large Block out canals in the cerebral spinal fluid
Describe parasites
- Eukaryotic organisms – Protozoa and Helminths
- Term parasite - sometimes applied to any microbe that lives in or on another animal host, causing it harm.
- Different morphology and sizes at different life cycle stages
- They can be microscopic or visible to the eye
- Multicellular
Describe protozoa
- Single cells 5 to 300 μm
- Single or multiple nuclei
- Haploid DNA
- Morphology varies throughout life cycle
- May have flagella.
- Trophozoites, cysts and other morphotypes – complex life cycles
Give examples of protozoa
- Entamoeba histolytica - amoebic dysentery
- Giardia lamblia – giardiasis (steatorrhea)
- Toxoplasma gondii
- Cryptosporidium spp - swimming pools - diarrhoea
- Trichomonas vaginalis –common STI
What are the groups of parasites?
- Cestodes are tapeworms e.g. Taenia saginata
- Trematodes are flatworms or flukes and include Schistosoma haematobium
- Nematodes which are roundworms e.g. Ascaris lumbricoides
What are helminths?
These are multicellular parasitic worms
• Different morphology and sizes at different life cycle stages
• They can be microscopic or visible to the eye
• Multicellular
