Lab 1 Flashcards
Explain aseptic technique?
Using practices and procedures to prevent contamination from pathogens
Steps of 4 way streak method? (12 points)
- disinfect the work bench
- ensure Petri dish and agar have been sterilised in autoclave
- turn on Bunsen burner, stops agar media getting contaminated with unwanted bacteria
- sterilise inoculating loop in Bunsen burner flame
- Remove lid from bacterial bottle and put neck of bottle in flame to kill unwanted bacteria
- dip inoculation loop into microorganism solution and make streaks on surface of agar
- flame the inoculating loop again
- turn agar plate 90 degrees and make streaks using the original bacteria streak
- repeat this process, allows the bacteria to spread out and grow in individual colonies
- replace lid on agar plate
- incubate at 37 degrees to allow for growth
- always label agar plate
Blood agar is made from?
Sheep’s blood
What type of medium is a blood agar?
Non selective medium
What is haemolysis?
A phenomenon whereby bacteria growing on a blood agar produces enzymes which break down red blood cells
Beta-haemolysis is?
Complete breakdown of red blood cells, transparency around bacterial colony
Alpha-haemolysis is?
Partial break down of red blood cells, partial clearing around bacterial colony with a greenish-brownish appearance
Non-haemolytic (gamma-haemolysis) is?
No breakdown of red blood cells
What type of mediums are a mannitol salt agar?
Selective and differential
Why is MSA a selective medium?
The high salt content inhibits the growth of other bacteria but allows Staphylococci to grow
Why is MSA a differential medium?
Because Staphylococcus aureus ferments mannitol releasing an acid which changes the colour of the colonies and surrounding agar to yellow
What bacteria grows on a MSA?
Staphylococci
Why does Staphylococcus epidermidis remain pink on an MSA?
Because it cannot ferment mannitol
Which bacteria tend to be pathogenic?
Beta-haemolytic bacteria
