rp6 Flashcards
examples of aseptic techniques that could be used
wash hands with soap
disenfect surfaces - kill microbes
sterilise pipette
boil agar to prevent contamination
flame neck of bottle of bacteria to kill microbes
bunsen burner close - upward current of air draws air borne microbes away
lift lid of petri dish slighty so microbes dont enter
method to investigate effect of antimicrobial substance on microbial growth
prep area using aseptic technqiues
use sterile pipette to transfer bacteria from broth to agar plate using aseptic technqiues
why is it important to maintain pure culture of bacteria
bacteria may outcompete bacteria being investigated or could be harmful to humans
why hold lid with 2 pieces of tape instead of sealing completely
allows oxygen in so prevents growth of anaerobic bacteria which are more likely to be pathogenic
why use paper discs with water and no antimicrobial agent
acts as control
ensures antimicrobial prevented growth not paper disc
why incubate upside down
condensation drips onto lid rather than agar surface
what if irregular inhibition zones
repeat reading at different positions and calculate a mean
why not use higher antimicrobial conc
more bacteria killed so clear zones may overlap
why incubate at 25 or less
below human body temp so prevents growth of pathogens
explain presence and absence of clear zones
clear zones - antimicrobial diffuses out of disk into agar inhibiting growth of bacteria
larger clear zones = more bacteria killed so more effective antimicrobial
no clear zones means if antibiotic used bacteria may be resistant or antibiotic may not be effective against specific bacteria