39-ABX Inhibitors of protein synthesis Flashcards by craig brancato

what new classes of antibiotics were created to inhibit penicillin resistant bacteria?

Aminoglycocydes, tetracyclines, and macrolides

ex. streptomycin- a macrolide

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bacterial protein synthesis inhibitors

selectively block bacteria synthesis of proteins by targeting ribosomes in bacteria vs. humans

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ribosomes have how many sub units?

2 subunits
prokaryotes (bacteria) = 50S and 30S
Humans= 40S and 60S

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which antibiotics act on the 30S ribosome?

tetracyclines, aminoglycosides, spectinomycin (not used often)

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which antibiotics act on the 50S subunit

macrolides, chloramphenicol, dalfoprisint and clindamycin

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Tetracyclines:

T/F- do tetracyclines competitively block binding of tRNA to the 30 S subunit?

this prevents addition of new amino acids to growing chain

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T/F- do aminoglycocydes and spectinomycin bind to 30S subunit?

interferes with initiation of protein synthesis

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How do Macrolides, chloramphenicol and dalfpristin work?

block enzyme that catalyzes the bond between amino acid being formed by the bacteria

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Drugs that act on 30S subunit: Tetracyclines, aminoglycocides, aminocyclitol

what are the 5 aminoglycocides?

amikacin
gentamicin
neomycin
streptomycin
tobramycin

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What class are the mycins?

aminoglycocide

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What is the one anti-ribosomal drug that cannot be absorbed systemically?

aminoglycosides

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can aminoglycocides be used topically?

yes - for infections on skin, mucous membranes and ocular tissue

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Can aminoglycocides penetrate meninges?

poorly and if needed must be administered intrathecally

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are aminoglycocides metabolized?

excreted by kidneys with little reabsorbtion. it is proportional to the GFR

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what bugs are aminoglycocides indicated for?

aerobic gram neg bacilli

most commonly used drug agains G-

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which of the 5 aminoglycocides is least toxic

streptomycin- but it is also the least active against most G- bacilli

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what is streptomycin typicallly used to treat

TB and yersinia pestis, and Tularemia

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which aminoglycocides is most active against strains of P. aeruginosa?

tobramycin

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which aminoglycocides is most active against the family called bacteriaceae (e.coli, klebsiella, …)

Gentamycin

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how is resistance to aminoglycocides caused?

inactivation of the drug, decreased binding sites and decreased uptake by porins

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what are adverse effects of aminoglycocides

nephrotoxicity and ototoxicity

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T/F aminoglyces are MCC of drug induced renal failure?

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which aminoglyce is most nephrotoxic?

neomycin- it is limited to topical treatment for this reason

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Triple antibiotic creams (topicals with neomycin) mixed with what?

neomycin, bacitracin and polymyxin
bacitracin-covers gram +
polymyxin-covers gram -
neomycin- covers both

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Drugs that act on 30S subunit: Tetracyclines, aminoglycocides, aminocyclitol what is aminocyclitol?

spectinomycin- (often an alternative to ceftrioxone in the treatment of gonorrhea) similar structure to aminoglycocides

Drugs that act on 30S subunit: aminoglycocides, aminocyclitol, Tetracyclines, what are some of the tetracyclines

doxycycline- minocycline tetracycline tigecycline - this one is a compound and will be asked later

what is spectrum of tetracyclines

broad spectrum bacteriostatic that inhibit growth of gram + and Gram - , ricketsiae, spirochetes, mycoplasmas, chlamydiae

what is drug of choice for Rocky mountain spotted fever and LYME

tetracyclines

What else can tetracyclines treat?

mycoplasma pneumoneae, chlamydia, acne vulgaris, brucelosis, and others....

T/F tetracyclines are also added to some regimens to treat H. pylori and peptic ulcers

is there resistance to tetracyclines?

yes- because it was added to animal feed to promote weight gain. Fuckers!

what are some ADRs of Tetracyclines?

discoloration of the teeth, nephrotoxicity, hepatotoxicity and sometime photosensitivity

What is tigecycline?

it is a compound that has increased affinity for 30S ribosomes and decreased resistance mechanisms like other tetracyclines

what is tigecycline indicated for?

Skin and soft tissue infections caused by MRSA, e.coli, b. frag, enterofaecalis also complicated intra-abdominal infections

Drugs that act on the 50S ribosomes

Macrolide antibiotics | ketolide antibiotics

what ribosome do macrolides affect?

50S

what are some macrolides?

azythromycin clarithromycin erythromycin

how are macrolides usually administered?

orally but..... | erythromycin and azythromycin can be IV for serious infections like legionaires

when given orally is erythromycin bioavailable?

not so much. it is better topically

is clarythromycin and Azythromycin bio available from the gut?

yes and they achieve higher tissue concentrations this way

are macrolides metabolized?

yes - by the liver and excreted in bile and urine

what are some of the indications for macrolides?

G- and G+ bacteria that cause respiratory tract infections and pneumoniae Group A strep, pneumococci, chlamydiae, legionella

are macrolides effective against Klebsiella? (typical pneumonia)

which macrolide is used for chlamydial urethritis?

1 x dose of Azythromycin

which macrolide is most effective against H. pylori causing peptic ulcer disease?

Clarythromycin

what other drug mentions is added to regimens of H. pylori?

tetracyclines

is there resistance to macrolides?

it is gradually increasing

how have bacteria become resistant?

decreased binding to 50S ribosome, enzymatic inactivation, increased bacterial efflux

which bacteria are resistant?

most staphylococci, and pneumococci are increasingly resistant

what are the adverse effects of macrolides?

largely devoid of toxicity- but can cause stomatitis (inflamm. of the mouth) nausea, anorexia, abdominal discomfort and diarrhea

what ADRs does erythromycin have on the gut

it binds to receptors for Motilin decreasing peristalsis. this causes N/V/D

do macrolides have drug interactions?

erythromycin and clarythromicin inhibit Cytochrome P450

T/F if erythro and clarythromycin interact with carbemezapine (anticonvulsant) it will cause life threatening toxicity?

T- carbemezipine toxicity

other macrolide interactions?

simvistatin, and lovastatin

what is the second class of drug that works on the 50 S ribosome besides macrolides?

Keolides antibiotics telithromycin clindamycin chloramphenicol

Are ketolide abx similar to macrolides?

yes they are similar in structure and act of 50S ribosome

example of ketolide abx

telithromycin- more stable in the stomach and increased ribosomal binding affinity. less susceptable to bacterial efflux

what are some indications for telithromycin?

approved for mild to moderate CAP-community acquired pneumoniea streptococcus pneumoniae, chlamydia, and mycoplasma pneumoniea.

ADR's of telithromycin

most common is Diarrhea and Nausea hepatotoxicity, and QT interval prolongation, respiratory failure and myasthenia gravis, LOC

what class is clindamycin?

a ketolide drug belonging to macrolides group

what does clindamycin cover?

G+ cocci, aerobic organisms such as B. frag and clostridium difficile

how is clindamycin administered

orally, parenterally, or topically

ADRs for clindamycin?

severe diarrhea caused by c. diff and pseudomembranous colitis which can cause death

what is chloramphenicol?

it is a drug that acts on 50S ribosome but unlike macrolides.

what makes chlormaphenicol different?

it is highly lipophilic, well absorbed in gut, and concentrates in CNS.

because it concentrates in CNS what is it affective against?

meningitis

what can chloramphenicol cause in neonates?

gray baby syndrome- reduce the dose

what is gray baby syndrom characterized by?

cyanosis, weakness, respiratory depression, hypotension, and shock

other adverse effects of chloramphenicol include?

2 forms of anemia 1. dose dependent anemia- reversible 2. fatal aplastic anemia- not reversible

T/F chloramphenicol is narrow spectrum abx?

F it is broad spectrum and is active against pneumococci, meningococci, and H. influenzae all the MCC of meningitis

Quinupristin- Dalfopristin

are the only streptogramin abx available.

what do Quinupristin- Dalfopristin do

they synergystically inhibit bacterial protein synthesis one prevents addition of new aminoacids other blocks bond formation

what are other protein synthesis inhibitors?

linezolid, | mupiricin-bactroban

what is linezolid indicated for?

Vanco resistant E. faecium pneumonia

ADRs of linezolid

thrombocytopenia, serotonin toxicity

what is mupiricin?

bactroban

what is mupiricin effective against?

staphylocci, group B hemolytic strep, empetigo | and nasal MRSA!!! boom