Lecture 9 and 10 Flashcards
What was Louis Pasteur investigating when he discovered pasteurisation?
Fermentation (wine preservation)
What did Pasteur discover among the yeast?
Bacteria
What theories did Pasteur have?
Germ theory: cells germinate, cause spoilage
Germs could be killed by heat to prevent spoilage
Who is the ‘father of antispetic surgery’?
Sir Joseph Lister
What did Joseph Lister do?
Disinfection of wounds/hands/surgical instruments/rooms using carbolic acid (phenol)
Who discovered penicillin?
Alexander Fleming
What bacteria produces inhibitory substance penicillin?
Penicillium notatum
How does penicillin kill?
Interfering with cell wall production which ruptures as E.coli size grows
Who developed a method to extract large amounts of penicilin from the mould?
Sir Ernst Chain
Lord Howard Florey
Define sterilisation
Removal of all forms of microbial life
How are things sterilised?
Pressured steam/gas
What is commercial sterilisation?
Sufficient heat to kill Clostridium botulinum endospores in canned food
What is disinfection?
Destruction of vegetative pathogens on inaminante objects
What is antisepsis?
Destruction of vegetative pathogens on living tissue
What is degerming?
Removal of microbes from a limited area
What is sanitisation?
Lowering microbial counts on eating/drinking utensils
What is biocide/germicide?
Kills microorganisms
What is bacteriostasis?
Inhibition of growth/multiplication of bacteria
What name is given to the length of time it takes for 90% of the population to be killed?
Decimal reduction time
What are three methods of action of microbial control agents?
- Alteration of membrane permability
- Damage to proteins
- Damage to nucleic acids
Give an example of damaging nucleic acids.
UV causes thymine dimers to form
What is the main type of bacteria that produces endospores?
Gram positive bacteria living in the soil
Why do soil bacteria produce endospores?
- Soil environment can’t be controlled
- Competition
- Environment can dry out etc.
How can microbial control agents be evaluated?
Use- dilution test
Disk diffusion method
How is the use-dilution test carried out?
Dip metal carries in test bacteria and dry Place in control agent Incubate (10 mins) at 20C Place carriers in growth medium Incubate 48 hours Number of cultures that grow
What is disk diffusion method?
Disks soaked in control agent placed on agar with test bacteria, measure zone of inhibition
What name is given to the lowest temperature at which all microorganisms in a liquid are killed in 10 minutes?
Thermal death point
What is thermal death time?
Minimal length of time all microorganisms in a liquid are killed at a given temperature
What is decimal reduction time?
Time required to kill 90% of the micoorganisms
What is the temperature used in an autoclave?
121C
What is the pressure in an autoclave?
15psi
How long is an autoclave run for?
15min for 10ml volume
What can’t an autoclave kill?
Prions
What temperature and time is required for pasteurisation?
72C for 15 seconds
What is the temperature and time for ultra high-temperature treatment (UHT)?
140C for 4 seconds
What are phenolics?
Derivative of phenol, less irritating
How do phenolics work?
Destroy lipids in cytplasmic membrane
How does triclosan (a phenolic) work?
In soaps/toothpaste etc.
Inhibits enzyme for lipid biosynthesis
Name a chemical agent for microbial growth that has a broad spectrum of activity
Biguanides (chlorhexidine)
What does chlorhexidine not work against?
Psyedomonads (Gram negative)
Endospores
What halogens are used to control microbial growth?
Iodine, chlorine
What does iodine do?
Impair protein synthesis
Alter cell membrane by forming complexes
What is an iodophore?
Iodine combined with organic molecule, less irritating
Name an iodophore
Povidone-iodine
What does chlorine form with water?
Oxidising agent hypochlorous acid (HOCl)
How do alcohols work?
Denature proteins and lipids
What do alcohols work against?
Bacteria and fungi
What do alcohols not work against?
Endospores, non-enveloped viruses
What heavy metals are used as microbial control?
Silver, mercury, copper
How do heavy metals control microbial growth?
Combine with sulfhydryl groups (cysteine, methionie) denature proteins
Where is silver used?
Dressing to treat infections with antibiotic-resistant bacteria
Where is mercury used?
Paint to prevent mildew
Where is copper used?
Reservoirs, ponds, swimming pools, fish tanks (its algicidal)
How do aldehydes (formalin, glutaraldehyde) work?
Denature proteins through covalent cross linkning
What are the 5 main sites antibiotics target?
Cell wall synthesis Protein synthesis Nucleic acid replication/transcription Plasma membrane Essential metabolite synthesis
Name a living antibiotic (not in use yet)
Bdellovibrio
