1/17
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced |
---|
No study sessions yet.
what are bioassays used for and why
to estimate the concentration of antibiotics in solution
monitor the concentration of an antibiotic in the blood
what does zone of growth inhibition indicate in bioassays
the edge of the zone occurring when the antibiotic is too dilute to inhibit growth of the bacteria
in bioassays what does it mean if there is a wider zone of growth inhibition
the antibiotic is more concentrated
how graph can be drawn using bioassays
standard curve can be drawn by plotting the zone of inhibition diameter against the antibiotic concentration. This curve can then be used to determine the antibiotic concentration in an unknown sample
what are antibiotics synthesized by
bacteria and fungi
how is the sensitivity if bacteria to antibiotics determined
disc diffusion; zones of growth inhibition for test organism are compared with those of a known standard sensitive strain
zones obtained with different antibiotics cannot be directly compared
what needs to be considered for antibiotic sensitivity testing
culture medium, inoculum density, antibiotics discs, incubation conditions, and interpreation of zone size and break points
what are two ways antibiotic resistance is aquired
chromosomal mutations or transfer of plasmid determined resistance
how do chromosomal mutations work
they impact the functionality of an antibiotic by altering the antibiotic target so it is no longer susceptible however the functionality is maintained
how does rifampicin work
binds to enzyme RNA polymerase blocking the ability of the bacteria to transcribe DNA to RNA
chromosomal mutations and Rifampicin
mutations in the chromosomal genes coding for RNA polymerase result in an altered enzyme to which rifampicin no longer binds while maintaining correct enzyme functionality
does plating on rifampicin containting media induce RifR mutants
no it does not induce mutants since mutants are already present it only selects for the mutants
how is the frequency of rifampicin resistant mutants deterined
no of RIFr coloines/ml divided by starting culture viability count
what is bacterial conjugation
transfer of genetic material between bacterial cells via cell to cell contact of the pilus
what does the R plamsid carry
carries the gene for chloramphenicol resistance (CmR), conferring resistance to the antibiotic on bacteria harboring this mobile genetic element
what is the R- bacteria sensitive to
nalidixic acid
MIC
minimum inhibitory concentration=lowest concentration of a substance that inhibits growth of an organism
how is MIC determined
agar dilution method which testing several strains on doses at once