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85 Cards in this Set

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microbial metabolites or synthetic analogues inspired by them that inhibit the growth and survival of microorganisms without serious toxicity to the host
antibiotics
_______ _______ is the key concept of antibiotics
selective toxicity
Initially extracts of _________ were screened simply for their ability to kill pathogenic microorganism in vitro... those that did were pushed through complex tests in attempts to discover clinically useful agents
fermentations
______ ________ _______ coupled with high throughput screening make it possible to screen hundreds of thousands of compounds for antimicrobial activity in a short time
combinatorial chemical synthesis
Some bacteria are immune to treatment from the outset because of what two reason?
1. they do not take up the antibiotic
2. they lack the susceptible target
Almost all antibiotics have the capacity to be ________ in vitro
bactericidal
To kill bacteria if the concentration or dose is sufficiently high
bactericidal
At lower concentrations bacterial multiplication is prevented even though the microorganism remains viable... what type of action?
bacteriostatic action
The smallest concentration that will kill a bacterial colony is the ________ bactericidal concentration
minimum
What is the difference between a minimum bactericidal dose and a bacteriostatic dose?
characteristic of given families of antibiotics
What happens if a bacteriostatic antibiotic is withdrawn prematurely from a patient?
microorganism can resume growth and infection can reestablish itself because the culture is still alive
This type of agent will interrupt the fulminating state (rapid growth) and give the immune system a chance to deal with the disease, with cure usually following
bacteriostatic agent
The first concentration which produces no visible growth is known as
minimum inhibitory concentration (MIC)
The last concentration that produces no visible growth is known as
minimum bactericidal concentration (MBC)
What two factors helps determine which antibiotics are the best choice for certain diseases?
1. determining the specific disease
2. what susceptibility patterns are exhibited by the causative microorganism
Individual species of bacteria are associated with particular infective diseases and the specific antibiotics are more likely to be useful than others for killing them... this is known as
empiric-based theory
These antibiotics are derived from fungi and have names ending in the suffix -cillin
penicillins
These antibiotics are also fungal products and have names beginning with the prefix -cef
cephalosporins
These synthetic antibiotics have names that mostly end in the suffix -floxacin
fluoroquinolones
Some antibiotics are produced by fermentation of soil microorganisms belonging to various streptomyces species with names ending in suffix
-mycin
*streptomycin
Other antibiotics are produced by fermentation of various soil microbes known as micromonospora species and have names ending in suffix
-micin
*gentamicin
Some antimicrobial families have the potential of inhibiting a wide range of bacterial genera belonging to both gram+ and gram- cultures and are called what
broad spectrum antibiotics
Some antimicrobial families only inhibit a few bacterial genera and are called what
narrow spectrum antibiotic
The failure of microbes to be killed or inhibited by treatment. Can be INTRINSIC or ACQUIRED
resistance
When bacteria may not all be killed and survivors are thought to have been resting during the drug treatment time and therefore remain viable when tested subsequently
persistence
Some antibiotics exert a significant toxicity to certain microorganisms that persists for a time after the drug is withdrawn and the concentration of drug in the blood falls below the MIC
postantibiotic effect
Associated primarily with β-lactam antibiotics. It is a phenomenon in which low doses in vitro against certain bacteria (staphylococci and streptococci) produce lysis, whereas higher doses do not.
biphasic ("eagle") effect
Microbial resistance is mediated by the production of bacterial enzymes that attack the antibiotic molecule, changing its structure to an inactive form.
* A susceptible antibiotic is apparently less potent when larger numbers of bacteria are present in the medium than when fewer cells are employed. The more bacteria that are present, the more antibiotic-destroying enzyme that is present, and the more antibiotic that is required to overcome this to achieve the desired response. An antibiotic that is not enzyme modified is comparatively free of inoculum effects.
inoculum effect
Antibiotics are conveniently classified by their activity against microoraganisms depending on their reaction to this method
gram stain method
This type of gram stain is colored blue by contact with the methyl violet-iodine process
*due to outer membrane and thick cell wall surrounding
gram-positive stain
This type of gram stain is colored pink when treated with the red dye safranin
*lipopolysaccarides on outer membrane is responsible for this
gram-negative stain
Gram stain is dependent on what layer of bacterial cells to determine the infectious bacteria and decide on which therapy is appropriate
the outer layers of the bacterial cells
What is one common bacteria that is neither gram-positive or gram-negative and has waxy cells
*acid-fast
mycobacteria
Anitbiotic Use in the Absence of Infection:
This use of antibiotics is used in preoperative bowel sanitization and orally for treatment of viral sore throats
prophylactic use
Anitbiotic Use in the Absence of Infection:
This use of antibiotics is used to help animals grow more rapidly to marketable size
*may potentially contaminate food we consume or provide reservoirs of drug-resistant enteric microorganisms
agricultural use
Are antimicrobials modeled after any natural product?
NO, only antibiotics
Sulfonamdies, Trimethoprim, Quinolones and Methenamine are all examples of antimicrobials or antibiotics?
antimicrobials
These are inhibitors of bacterial cell wall biosynthesis or inhibitors of protein biosynthesis
antibiotics
β-lactams: Penicillins, Cephalosporins, Carbapenems, and Monobactams are all examples of what type of antibiotics
cell wall biosynthesis inhibitors
Aminoglycosides, Macrolides and ketolides, Tetracyclines, and Cyclic peptides are all examples of what type of antibiotics
protein biosynthesis inhibitors
This red dye has been proved to be active in vivo against streptococcal infections and it is a SULFONAMIDE
prontosil rubrum
Sulfanilamide is a colorless cleavage product formed by reductive liver metabolism of this prodrug sulfonamide
prontosil rubrum
MOA of this drug:
microbial biosynthetic pathway leading to TETRAHYDROFOLIC ACID SYNTHESIS results in this drug used as a false metabolite and inhibits the enzyme dihycropteroate synthesis. It competes for the active PABA site.
MOA of sulfonamides
How can the antimicrobial efficacy of sulfonamides be reversed? By adding....
significant quantities of PABA into the diet
This sulfonamide stands out because although it is administered orally it isn't absorbed in the gut and the majority of the dose is delivered to the distal bowel
sulfasalazine
This prodrug sulfonamide undergoes reductive metabolism by gut bacteria and converts into sulfapyridine and 5-aminosalicyclic acid (active)
*used for ulcerative colitis and Crohn's disease
sulfasalazine
This antimicrobial inhibits dihydrofolate reductase and therefore prevents biosynthesis of folic acid derivative and the thymidine required for DNA
trimethoprim
This class of antimicrobials are rapidly bactericidal and inhibit DNA gyrase and topoisomerase IV (key bacterial enzymes that dictate conformation of DNA)
quinolones
These antimicrobials comprise a group of synthetic substances possessing in common an N-1-alkylated 3-carboxypyrid-4-one ring fused to another aromatic ring, which itself carries other substituents.
quinolones
This class of antimicrobials were of little clinical significance until the discovery of the addition of a fluoro group to the 6-position, which greatly increased the biological activity
quinolones
*fluoroquinolones
This is the first of the second-generation quinolones and has a broad spectrum and equivalent in potency to many of the fermentation derived antibiotics
norfloxacin
These two drugs dominate the worldwide flouroquinolone market
ciprofloxacin and levofloxacin
What ability do quinolones have that other drugs to not that decreases solubility and reduces drug absorption?
they can CHELATE polyvalent metal ions
This antimicrobial is used for disinfection of acidic urine and and recurrent UTIs and is made of ammonia and formaldehyde (-->active component)
methenamine
This name is given to cyclic amides
lactam
This (inhibitor of cell walls) is a cyclic amide with four atoms in its ring with the contemporary name of azetidinone
*rare structural feature of penicillins
β-lactam
What type of shape do penicillins have with the β-lactam ring fused to the 5-membered thiazoldine ring?
a "V-shape"
What is the most UNSTABLE bond in the penicillin molecule? It breaks down quickly in basic solutions to produce penicilloic acid-->penilloic acid
β-lactam amide bond
Is the conversion of penicilloic acid-->penilloic acid reversible or irreversible under physiologic conditions?
Irreversible
What bacterial enzyme catalyzes the hydrolysis reaction of β-lactams (penicillins)?
β-lactamase
In what type of solutions is the hydrolysis of penicillins complex?
acidic solutions
Do the three products (penicillamine, penilloic acid and penilloaldehyde) of acidic degradation of penicillins have antibacterial activity?
NO antibacterial activity
What subunits to antibiotics bind to on the bacterial cell?
30S and 50S subunits
Interference with bacterial protein biosynthesis prevents repair, cellular growth and reproduction... the action of what?
antibiotics
This class of antibiotics contains a pharmacophore consisting of either streptamine, 2-deoxystreptamine, or spectinamine
aminoglycoside
These antibiotics are freely water soluble, basic and not absorbed much in the GI tract and are excreted in active form in urine
aminoglycosides
These antibiotics are administered either by IM or perfusion
aminoglycosides
MOA of this class of antibiotics:
Bind to external lipopolysaccaride and diffuse into the cell to destroy the membrane
aminoglycosides
This class of antibiotics kills mainly gram-negative bacteria
*high toxicity potential so limits their clinical use to severe gram-negative infections
aminoglycosides
This is the most important aminoglycoside antibiotic, it is water loving and opportunistic
gentamicin
This aminoglycoside antibiotic is incompatible with β-lactam antibiotics and causes inactivation of both if used together
gentamicin
This antibiotic is a mixture of several antibiotic components produced by permentation of micromonospora purpurea and other soil microorganisms
gentamicin
This antibiotic (aminoglycoside) is frequently used for burns, pneumonias and UTIs and is highly virulent
gentamicin
These antibiotics are large lactone rings that are 14-membered
macrolides
*macro=big
These antibiotics have four fused 6-membered rings
tetracyclines
These antibiotics have many adverse affects and a high incidence of resistance which decreases their use
tetracyclines
What is the main important feature of tetracyclines that can form salts?
chelation
This class of antibiotic drugs can cause yellowing of the teeth because it is yellow and it is incompatible with antacids
tetracyclines
What two classes of drugs have the ability of chelation?
tetracyclines and quinolones
Tetracyclines bind to the ____ subunit of bacterial cells while chloramphenicol binds to the _____ subunit
*both are broad spectrum protein synthesis inhibitors
30S and 50S
This type of antibiotics is very toxic to humans and are used with common and uncommon amino acids with D absolute stereochemistry and a pendant fatty acid chain
cyclic peptides
One of the consequences of the unusual architecture of these antibiotics is that these glycopeptide agents are not readily metabolized
cyclic peptides
MOA for this class of antibiotics:
Attach to bacterial membranes and interfere with their semipermeability so that essential metabolites leak out and undesirable substances pass in
cyclic peptides
This type of cyclic peptide is highly associated with adverse infusion related events
*too rapid of a rate will cause red mans rash, other bad rxns
vancomycin
High doses of vancomycin can cause what two major adverse effects
nephrotoxicity and ototoxicity (auditory damage-my be permanent)