Lecture 2 - Antibiotics Flashcards
Sterilization refers to killing _____ microorganisms using any one of three methods:
- ____ heat which results in carbonization and is typically used to sterilize ____ or metal. It requires a heat of ____ degrees C for 2 hours.
- Autoclave which results in _____ denaturation and is used to sterilize _____ or metal as well. It requires 121 degrees C with water pressure.
- Gas, which contains an _______ agent which is toxic to microorganisms. This method is particularly useful for materials that can’t withstand high heat, and it requires about 10% concentration for 6 hours.
ALL microorganisms
DRY
Glass
160 degrees C for 2 hours
PROTEIN
Glass
Alkylating
Disinfection refers to killing off of most, but not all microorganisms. One disinfecting method is ______ which results in the physical removal of microorganisms and should be used for _____ labile liquids (i.e. serum.) However, this method does not remove ______, which are typically too small to be removed with this method.
Filtration
HEAT labile liquids
Viruses (too small)
_____ is an antiseptic used in soaps, cosmetics, and plastics. It’s also used to treat _____ outbreaks, but there is concern that overuse could lead to induction of ______ resistance.
TRICLOSAN
MRSA
ANTIBIOTIC
______ and ______ are the two biggest considerations when developing/using antibiotics.
Selectivity and Spectrum
______ refers to the ability of antibiotics to kill microorganisms without harming the patient. This relies on the ability of the antibiotic to target aspects of the microorganism which are essential for its function that are not essential for functioning of the patient’s cells. A related concept is ______ index which is calculated as the ____ dose/ _____ dose.
Selectivity
Therapeutic index
Toxic dose/ Effective dose
______ refers to the ability of an antibiotic to specifically target certain microorganisms or to target many microorganisms (Narrow vs Broad.)
Spectrum
______ antibiotics kill bacteria while _______ antibiotics inhibit the growth of bacteria. The latter is a good option when the ______ system is intact and antibodies can reach the site of infection (Abs don’t cross the BBB.)
Bacteriocidal
Bacteriostatic
Immune
There are 5 key mechanisms of antibiotic resistance.
- Antibiotic destruction or _______
- ______ resistance due to absence or modification of target.
- Altered _____ to bypass antibiotic target.
- Inability of antibiotic to reach target.
- ______ that remove the antibiotic from the cell.
Modification
Intrinsic
Metabolism
Pumps
______ is a relatively toxic antibiotic that is used topically. It blocks the recycling of ________ (BP) which normally becomes a carrier of newly synthesized _______ repeat units.
Bacitracin
Bactoprenol
Peptidoglycan
_______ is an antibiotic that tightly binds D-ala-D-ala, preventing both _______ and _______ reactions necessary for cross-linking and elongation of peptidoglycan chains, respectively. Because its relatively large, it can only be used against gram ___ bacteria. High level resistance is mediated by _____ that alter peptidoglycan synthesis so that there is no D-ala-D-ala intermediate.
Vancomycin
Transpepidation
Transglycosylation
Positive (+)
Transposons
Three high-level vancomycin resistance genes are:
- Van H, a ______ which converts pyruvate to D-______
- Van A, a _____ which forms D-ala-D_____ (this can be used in place of D-ala-D-ala by the bacteria.)
- Van X, a _______ which breaks apart D-ala-D-ala. The end result is that bacterial transpeptidase can recognize and carry out its function on D-ala-D-____, which vancomycin cannot.
Reductase
D-lac
Ligase
D-ala-D-lac
Dipeptidase
D-ala-D-lac
______ binds tightly to the active site of _____, thus competitively inhibiting its function. This leads to decreased _____-linking of peptidoglycan chains and decreased cell wall stability.
Penicillin
Transpeptidase
Cross-linking
Modifications of the ____-groups of antibiotics influence their activity, spectrum, and pharmacology.
R-groups
Some organisms can exhibit penicillin resistance. Mechanisms for this include:
- Permeability (with respect to Gram - bacteria.
- ______, an enzyme that cleaves the _____ ring.
- A mutation in the ______ enzyme –> penicillin can no longer bind it.
Beta-lactamase
Beta-lactam
Transpeptidase
_____ acid is a molecule that targets ______. Given together with penicillin (augmentin), it increases the efficacy of penicillin by blocking resistance to it.
Clavulinic acid
Beta-lactamase
