lecture exam #3 Flashcards
thermal death point
the lowest temperature at which all microbes in a fluid culture will be killed in 10 minutes.
thermal death time
the minimal time required to kill all the bacteria in a liquid culture at a given temperature.
decimal reduction time
the length in time at which 90% of a bacterial population will be killed at a given temperature.
Kirby-Bauer Test
measures the zone diameter of the ABX compared to a table.
MIC: minimum inhibitory concentration. the smallest effective dose to inhibit growth.
inversely related to the zone of inhibition.
small zone = big MIC : need more chemicals to inhibit growth.
big zone = small MIC : less chemicals needed to inhibit growth.
E-Test
determines MIC using an epsilometer with the ABX.
only tests one drug.
broth dilution test
determines the MIC (minimum inhibitory concentration) and the MBC (minimal bacteriocidal concentration).
tests if the bacteria is able to grow at all ABX concentrations, when its resistant and sensitive.
therapeutic index
the ratio of a drug dose that is toxic to humans compared to the minimal effective dose.
assesses the risks against the benefits.
TI = TD50/ED50
TD50: toxic dose to 50% of the population
ED50: effective dose to 50% of the population.
! safety zone: a larger zone is better for over the counter while a narrow zone must be monitored by the hospital.
ID50
infectious dose.
the dose that will cause an infection to 50% of the population.
measures the virulence.
high ID50: means you need to encounter more microbes in order to get sick. therefore, it is less potent.
low ID50: means you need to encounter less microbes in order to get sick. therefore, it is very potent.
LD50
lethal dose.
the lethal dose for 50% of the population.
measures the amount of toxins released by the microbe that harm the host.
a high LD50 = low virulence. you need a larger volume/dose of the toxin for it to be lethal.
low LD50 = high virulence. you need a smaller volume/dose of the toxin for it to be lethal, very potent!
