Antibacterial Basics Flashcards by andrew ryser

Antibiotics (ABs) are substances produced to kill microorganisms or to protect from toxins produced by microorganisms, what are the 3 ways ABs are produced?

by microorganism
precursor by microorganism - semi synthetic
synthetic

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in 1936 what noted to kill streptococci?

sulfanilamide

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what was discovered in 1928 and began mass production of it in 1941

penicillin

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most of the over 100 AB drugs in clinical use are what?

semi synthetic

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What are the properties of a ideal AB

stability, Solubility, diffusibility (crosses the BBB), slow excretion (protein binding, drug combos), and large therapeutic index= SELECTIVE

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PEN G (Benzyl penicillin) vs PEN V (phenoxy-benzyl penicillin), which one is stable in acids thus can be take orally

PEN V is stable in ACIDS

PEN G is NOT stable in acids

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Therapeutic index = TD50 / ED50
what is TD 50?
what is ED50?
do you want a large or small Therapeutic index?

TD50= toxic dose
ED50= effective dose
want a HIGH therapeutic index bc that means drug is safer and more SELECTIVE

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the microbe response to a AB can be resistance or secondary products of bacterial destruction, what 3 things are taken into consideration when resistance by a microbe is occurring?

resistance tells you to consider:

choice of drug
the dosage of the drug
drug combos

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what 5 ABs are considered Bacteriostatic?

sulfonamides
trimethoprim
tetracyclines
erythromycin
Vancomycin*

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what 5 ABs are considered Bactericidal?

Vancomycin *
quinolones
penicillins
cephalosporins
aminoglycosides

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what is the 1 AB that was considered bactericidal but due to INC resistance has led to it becoming more of a bacteriostatic drug

Vancomycin

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what do bacteriostatic drugs do

bacteriostatic drugs stop the growth of that microbe. so on a graph static drugs will just halt the growth thus not allowing microbe to inc in number

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what do bactericidal drugs do

bacteriocidal kills the microbe! so on a graph cidal drugs will bring the amount of microbe to 0

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what is prophylaxis?

how much AB drug use is for prophylaxis?

prophylaxis temporarily decs the most likely pathogens below a critical level required to cause infection.
Prophylaxis accounts for .25-.5 of AB drug use

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what is empiric therapy?

initiation of treatment (tx) before etiology of infection is known with agents known to be effective against the most likely pathogen acquired (suspected from source of infection)

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what are the differences between gram + and gram - bacteria

gram + : many lactamases, thick cell wall of peptidoglycans, membrane has PBPs, 1 cell membrane

gram - : few lactamases, thin cell wall of 1-2 layers of peptidoglycan, 2 cell membranes, 1 on outside then cell wall layer then 2 cell membrane

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What is MIC

MIC - minimum inhibitory concentration - the lowest concentration of drug which completely inhibits growth at 24 hrs

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what is MBC

MBC- minimum bactericidal concentration

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what does Vancomycin work against?

GRAM + bacteria!

Too big to work against gram -

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what is the note about choosing a AB

once sensitivity profile is known, choose the effective drug with the narrowest spectrum to avoid emergence of resistance microbes

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what variables are used to determine AB sensitivity? aka susceptibility guided therapy.

MIC
MBC
disk diffusion assays and etest

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what is the Gold Standard for determining MIC

Broth dilution assay

the location of infection is important for choosing AB and agents in the CNS are hard to treat, what kind of AB will treat a CNS infection

ABs that are lipophilic that can cross the BBB will treat a CNS infection

what are the variables of pharmacokinetics that need to be taken into consideration about ABs?

ADME+T

absorption, distribution/ excretion, metabolism + toxicity (nephro, ototoxicity, hypersensitivity)

Metabolism is important in Prodrugs why?

Prodrugs require activation and are based on cytochrome p450 activation or inactivation

What host factors must be considered when prescribing a AB? | what is the importance of age?

age (young people metabolize, clear drugs faster than older) allergies, food/ hydration (Ca can limit absorption of ciprofloxacin) hepatic function (will pro drug be activated?) pharmacogenetics (fast vs slow metabolism) pregancy immune status

Describe the 3 AB cocktail situations a) empiric therapy b) mixed infections c) synergism

a) empiric therapy- for serious infections of unknown etiology b) mixed infections: intra abdominal- potentially several microbes, use 2 narrow spectrum ABs c) synergism: more than additive effects of using 2+ ABs, different MoA leading to one drug making the other more effective

An example of synergism is use of B lactam and aminoglyoside combo, what are the functions of each and how is this synergism?

B lactam: cell wall synthesis inhibitors Aminoglycosides: inhibitors of protein synthesis use of B lactam compromises cell walls allowing Aminoglycosides to accumulate inside the cell thus killing it

An example of synergism is the use of trimethoprim and sulfamethoxazole, what is the combo used for?

tx of gram - urinary tract infections

what is antagonism? what example was provided?

antagonism- less than additive effects. use of bacteriostatic drug with B lactam, bacteriostatic drug inhibits cell growth thus requiring no new cell wall synthesis making B lactam useless

what 4 ABs of inhibitors of Nucleic acid synthesis? | 2 classes describe the two classes and the drugs in each class

Inhibits folic acid synthesis= sulfonamides, trimethoprim and antifolates RNA synthesis inhibitor= Rifampin

Rifampin does what

inhibits RNA synthesis

sulfonamides, trimethoprim and antifolates do what

inhibits folic acid synthesis

What 4 Abs are DNA damaging agents?

quinolones Nitrofurantoin Metronidazole Methenamine

what do quinolones do?

DNA gyrase A, Topoisomerase 4 inhibitors

what do Nitrofurantoins do?

free radical generator

What do Metronidazoles do?

anaerobic enzymatic reduction then metabolite DNA binding

What do Methenamines do?

breaks down to form formaldehyde which alkylates DNA and protein

what 3 ABs are inhibitors of cell wall synthesis

B Lactams Vancomycin Bacitracin

``` What do B lactams do? What drugs are under the class of B lactams? ```

``` B lactams inhibit the transpeptidation cross linking of peptidoglycan B lactams include: penicillin cephalosporins, monobactams (aztreonam) carbadpenems (imipenem) ```

what does Vancomycin do? | what bacteria does Vancomycin work against?

Vancomycin binds to D-ala-D-Ala preventing polymerization of cell wall components Vancomycin= Gram +!!

what does Bacitracin do?

binds to and prevents functioning of lipid carrier of peptidoglycan

Penicillin is what type of drug and MoA?

penicillin is a beta lactam that inhibits cell wall synthesis by inhibition of transpeptidation cross linking of peptidoglycan

What 2 Abs are responsible for damage of cell membrane?

polymyxins | daptomycin

polymyxins do what to damage cell membrane

polymyxins are cationic detergents that disrupts the cell membrane

daptomycin does what?

daptomycin is a lipopeptide that disrupts membrane function

cephalosporins are what type of drug and what is its MoA

Cephalosporins are a beta lactam that inhibits cell wall synthesis by inhibition of transpeptidation cross linking of peptidoglycan

What are the 7 (1 combo) Abs that are inhibitors of protein synthesis by ribosomal protein binding to 30s or 50s

``` aminoglycosides- bactericidal tetracyclines= bacteriostatic tigecycline macrolides clindamycin linezolid Quinupristin/ dalfopristin= bactericidal ```

monobactams are what type of drug and what is its MoA

monobactams are a beta lactam that inhibits cell wall synthesis by inhibition of transpeptidation cross linking of peptidoglycan

what are the 3 Abs under the class called macrocodes? and what are their MoA

Macrolides= erythromycin, clarithromycin, azithromycin | Macrocodes are inhibitors of protein synthesis

carbapenems are what type of drug and what are their MoA

carbapenems are a beta lactam that inhibits cell wall synthesis by inhibition of transpeptidation cross linking of peptidoglycan

what is a inhibitor of dihydrofolate reductase (DHFR) that is a structural analog of pteridine? is it bacteriostatic or tidal?

trimethoprim Trimethoprim is bacteriostatic!! can be tidal if with a sulfonamide

what is trimethoprims selectivity

very selective needs much higher concentration to inhibit human DHFR