Lab quiz 7 Flashcards
antimicrobial
a substance that inhibits the growth of or kills a microorganism
types of antimicrobials include…
those produced by other microorganisms
chemicals
natural compounds
Spices can be
bacteriostatic
bactericidal
You will make spice media using…
chilli
cloves
use of spices emerged as a method…
to control bacterial growth on food
bacteriostatic
prevent bacteria from reproducing
bactericidal
able to kill bacteria
antibiosis
inhibitory effect
“against life”
Inhibitory effect
once infected by one organism animal is protected from infection by another organism
antibiotic
inhibitory substance
metabolic product of one organism that in very small amounts kills or inhibits growth of other microorganism(s)
What are some organisms that produce antibiotics?
bacteria of genera Bacillus and Streptomyces
genus of mol- Penicillium
What are the most widely used antibiotics?
Penicillins and cephalosporins
broad spectrum antibiotic
antibiotic which has the ability to inhibit or destroy many different kinds of pathogenic organisms
What does penicillin inhibit
transpeptidation in final step of cell wall formation
Streptomycin
a broad spectrum antibiotic particularly active against Gram-negative organisms
What does streptomycin inhibit
protein synthesis
what do surfactants do?
attack the cell membrane by destruction of lipids in membrane of cell wall
What is the production of antibiotics a natural component of?
microbial competition for niche space
What does cross streak test?
capacity of a microorganism to produced antibiotic effective against any specified group of other microrganism
How does cross streak work?
streak antibiotic-producing isolate on agar then incubate
streak a number of “test organisms” perpendicular to original streak but don’t cross original
incubate
onserve the inhibition of growth of test organisms
What does sensitivity disk technique determine?
susceptibility of microorganisms to many different antibiotics
How does sensitivity disk work?
mix test organism wiht melted soft agar
pour inoculated soft agar onto base agar and let solidify
incubate and observe zones of inhibition
What factors affect size of inhibition zone?
rate of diffusion of the organism-produced antibiotic
density of inoculum
growth rate of organism
susceptibility to antibiotic
What cultures are used for antimicrobials
E. coli
B. cereus
Candida albicans (yeast)
Disinfectants
chemicals used on inanimate objects to decrease the number of microbes
antisepticcs
chemicals used on living tissues to decrease the number of microbes
At these concentrations these agents…
kill bacteria
are bactericidal
At low concentrations these agents…
only inhibit growth
are bacteriostatic
Bacteriostatics are useful for…
food preservation
chemotherapeutic agents
How do we test the antibacterial capacity of a chemical?
add test organism into a solution of chemical
make periodic transfers into growth medium to determine if organism has been killed
T/F there is a universal best agent for chemical control of bacteria
FALSE
some agents are more effective than others under defined conditions
What cultures are used for disinfectants/antiseptics?
E. coli
S. aureus
How are we testing disinfectants/antiseptics in this lab?
paper disc method
how does paper disc method work?
dipping sterilize paper discs into chemical agent
place disc on a soft agar layer seeded with bacteria
how is the effectiveness of the chemical determined in paper disc method?
size of the zone of inhibition
