Microbiology Flashcards
(23 cards)
Aseptic
Free from contamination by microorganisms
Working in a Sterile Bench Space
•work surfaces must be disinfected before and after use
•hands must be washed with antibacterial soap - before and after work
•any transfer of MO must be done close (20cm) to a bunsen burner
Why transfer of Mo done near Bunsen Burner
Warm air currents draw any airborne MO upwards
Accessing a Glass Container
On opening a flask, bottle or TT containing agar or a microbial structure - neck must be held over a Bunsen flame
Kill surface microbes
Removed the plug with little finger curled towards the palm
Accessing a Petri Dish
•agar plate prepared by pouring liquid sterile nutrient agar into sterile Petri dish - lid must be opened only one side to allow access
•to add anything to surface - petri dish lid must be only opened on one side for minimal time
Autoclave
Container using steam, prod under high pressure and temperature, to sterilise equipment
Items can be kept dry by wrapping tightly in tin foil
Flaming to Sterilise Instruments
•A wire loop, ster by heating w/ Bunsen, used to transfer a microbial culture (from existing cult on agar slope or nutrient broth) to a nutrient agar plate & sterilised afterwards
•Forceps used in transfer of antimicrobial discs - also ster by Bunsen
•L-Shaped Glass Spreaders ster by dipping in ethanol and then flamed
Securing a Petri Dish
•inoculated plate must be secured by fixing two or four short strips of adhesive tape at opposite ends of dish
How are dropping pipettes commercial sterilised
Irradiation
Transfer Images
Culture
A microbial structure is a nutrient medium (broth or agar surface) in which a specific microorganism can reproduce and multiply
Inoculum
A sample amount of material containing MOs used to start a new culture
Investigating Effectiveness of Diff Antibiotics - PREPARATION
•Sterile Petri dish containing sterile agar used
• Sample removed from broth culture using sterile dropper pipette
•few drops placed onto surface of agar
•sterile spreader used to spread inoculum over entire surface of agar
•inoculum allowed to dry
Investigating Effectiveness of Diff Antibiotics
•Sterile discs of filter paper are soaked in various antibiotics
•using sterile forceps, a disc is placed on agar plate
•4 diff antibiotics placed centrally within separate quadrants (or a Mast ring)
•Label underside of plate with initials, date, name of MO and antibiotic used
•Dish taped and placed in incubator at 20-25°C for 2-3days
Investigation of Effectiveness of diff antibiotics - AFTER INCUBATION
•plate will look opaque where bacteria have grown
• inhibition zones are clear zones where antibiotics have inhibited growth
•diameter IZ measured in mm / area determined by placing mm-squared paper below dish
•info used to determine which most effective at inhibiting growth
Mast Ring
Ring of paper with several ‘arms’ each treated with diff antibiotic
Minimal Inhibitory Concentration (MIC)
Lowest concentration of an antibiotic that inhibits the growth of a bacterial strain
Effective Concentration Antibiotic
low conc inhibits = effective
precise conc determined by prep an inoculated agar plate - adding e-strip and incubating culture
e-strip has exponential gradient of antibiotic concs on a paper strip
Patients w/ specific infection ab w/ low MIC score admin
Why may a dosage be several times the MIC score
Ensure effective treatment
Preventative evolution of antibiotic-resistant microbial strains
Preparing a Streak Plate to Isolate Single Colonies
•sterile wire loop used to remove sample from bacterial culture
•inoculum is smeared backwards and forwards across surface of agar
•Flame the loop, cool and turn Petri dish 90° before streaking inoculum across the surface of agar in parallel lines
•repeat process twice more
•after suitable period incubation, colonies of bacteria will have grown on agar
•In first areas will prob form continuous mat
•in final streaked area, should be small colonies formed by division of a single bacterial cell
Antimicrobial Properties of Plants
-some plants contain chemicals with antimicrobial properties- allow them to resist infection from bacteria and fungi
Reputably culinary uses (herbs & spices) or those that prod essential oils (lavender)
Investigating Antimicrobial Properties of Plants
Inoculated agar plates produced & sterile filter paper discs containing plant extracts are placed on the agar surface
To make a plant extract - 3g plant mat crushed in 10cm3 ethanol
Paper discs soaked in extract and allowed to dry before using
Incubated for 2-3 days and measurements made of any Inhibition Zones
If testing plant extracts for ANTIFUNGAL properties
sterile agar plate inoculated with a mould using a sterile wire loop - also used for spreading mould across surface
Fungi grow best at lower temp than bac - room temp incubation should suffice
