1. Introduction to microbiology
PSP1

2. virus

3. virus Smallest known infective agent
Most forms of life a susceptible to viral infection- humans, animals, plants, bacteria
Need a host to replicate
Requires entry to the host
Respiratory tract
Alimentary tract ( oral –faecal route)
Blood
Sexual intercourse
Skin abrasions

4. Basically :
a core of nucleic acid ( contains genetic material DNA/RNA) surrounded by a protein coat
Outer protein envelope

5. replication
Often protein envelope partially derived from the host cell
Virus always replicate INSIDE a host cell
Fragile outside a host cell
Cause cell lysis- viral DNA replicated
Remain latent within the cell , divide with the cells natural division , virus DNA is replicated during this division
THEN cause lysis

6. Different virus attack different cells depending on the RECEPTOR SITE
Systemic- spreads widely and infects many tissues and organs e.g. measles
Localised- invades only tissues adjacent to the site of entry e.g respiratory viral infections/ verrucae

7. Main defence of the body is to produce the protein interferon
Interferon is released by infected cells and taken up by other cells
Antibodies appear in the patient's serum- this leads to immunity or resistance

8. Hepatitis
Hepatitis A, Hepatitis B, and Hepatitis C are diseases caused by three different viruses
different modes of transmission and can affect the liver differently.
Hep A- ingesting faecal matter ( often associated with developing countries/travel)
Hep B- blood/body fluid
Hep C- blood/body fluid
There are vaccines to prevent Hepatitis A and B; however, there is not one for Hepatitis C.

9. HIV Human immunodeficiency virus AIDS- final stage of HIV infection
1 in 5 affected people do not know they have the virus
Transmitted through:
Unprotected sex
Mother-baby
Contaminated needles

10. bacteria

11. Single cell organisms
Classified in different ways ( three parameters):
Shape- morphology
Colour ( Gram staining)
Growth requirements-Need for oxygen

12. naming Bacteria are named with 2 words ( genus + species)
Staphylococcus aureus shortened to S.aureus

13. morphology Sphere ( cocci) Rods ( bacilli) Spiral (spirochaetes)
Staphylococcus – spheres bunch together
Streptococci- spheres form a chain
Rods ( bacilli)
Spiral (spirochaetes)

14. Gram staining
Gram positive and gram negative refers to how a bacteria reacts to a gram stain.
Chrystal violet then iodine
If it takes the initial stain, it will be purple and be considered gram positive.
If it doesn't take the initial stain, it will be pink and gram negative.

16. Positive and negative
The difference is the outer casing of the bacteria.
A gram positive bacteria will have a thicker layer of peptidoglycan (a sugar-protein shell)
A gram negative bacteria has an outer membrane covering a thin layer of peptidoglycan on the outside.

17. Growth requirements
Aerobes need oxygen and are found on wound surfaces
E.g. Pseudomona aeruginosa
Anaerobes cannot survive where there is oxygen and are found deep in wounds
E.g. Clostridium welchii – causes gas gangrene

18. Cultured on an agar plate

19. Staphylococcus aureus
Gram positive
Staphylococcus aureus is a bacterium that commonly colonises human skin and mucosa (e.g. inside the nose) without causing any problems. Normal body flora
Common wound infector- may lead to cellulitis
Methicillin Resistant Staphylococcus aureus

20. Pseudemonas aeruginosa
Common wound pathogen
Gram negative
Pyocyanin – green pigment secreted by the bacteria
One of the most worrisome characteristics of P. aeruginosa is its low susceptibility to antibiotics

21. Streptococcus pyogenes ( group A strep)
Gram positive
Faculative anerobe ( can survive with or without oxygen)
Part of normal flora in many people’s throats
Can cause simple infections ( sore throat) to life threatening infections
Most frequent pathogen in humans
There are also group B strep and group C but these are not comon wound infectors

22. Streptococcus pyogenes
Strep throat
Purulent infections
cellulitis
impetigo
necrotising fasciitis ( flesh eating)
Can lead to toxic shock

23. group G Strep MAY be found as part of normal skin flora
Normally infections in patients with other co-morbidities e.g diabetes
Wound infector
Can spread and cause extensive infections: e.g.
Bacteriamia
Septic shock

25. f
FUNGI

26. Fungal hyphae
Multicellular fungi are composed of filaments called ‘hyphae’

27. More complex organism than bacteria
Reproduce by spore formation ( released by splitting hyphae) or sexual reproduction ( mix chromosomes)
Cell wall+ cell membrane
Ergesterol essential element of the cell membrane – provides stability and flexibility

28. fungi on skin and nails DERMATOPHYTES infect keratinous material
NON-DERMATOPHYTES
Yeasts or moulds
Fungi cannot manufacture their own food. Dermatophytes ingest keratin as their food source

29. dermatophytes affecting the skin and nails
3 genera
Trichophyton
Epidermophyton
Microsporum
all endemic to communal areas

30. Pathology First result
Potassium hydroxide wet mount – dissolves Keratin leaving resistant Fungal hyphae- seen through microscope
Second result
Fungal culture- agar plate
Therefore 2 weeks for results to be returned from the pathology laboratory

31. Tricophyton rubrum