anti-biotics: Protein Synthesis Inhibitors Flashcards
protein synthesis inhibitors act on what ribosome subunits?
30s and 50s
what are the protein synth. inhibitors?
(AT CELLS)
Aminoglycosides
Tetracyclines
Chloramphenicol
Erythromycin (Macrolide)
Linezolid
Lincosamide (Clindamycin)
Streptogramins
what are the protein synthesis inhibitor drugs that act on the 30s ribosomal subunit?
aminoglycosides
tetracyclines
what are the protein synthesis inhibitor drugs that act on the 50s subunit?
Chloramphenicol
Erythromycin (Macrolide)
Linezolid
Lincosamide (Clindamycin)
Streptogramins
aminoglycosides will kill bacteria as long as they are what?
aerobic bacteria or gram negative bacteria, it does nothing to anaerobic
what are the aminoglycoside drugs?
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
Kanamycin
Netilmicin
how do aminoglycosides work?
they will bind to the 30s ribosomal subunit and inhibit bacterial protein synthesis
it will inhibit the initiation complex which induces misreading of mRNA
how are aminoglycosides administered?
can it be orally?
parentally (intramuscularly and intravenous)
not orally, barely absorbed
how can bacterial resistance be acquired to aminoglycoside drugs?
bacterial transferase enzymes inactivate the drug by:
phosphorylation, adenylation, and acetylation
Essentially resistance is acquired by altering the structure of the antibiotic
all protein synthesis inhibitors have good activity towards what bacteria?
gram negative aerobic bacilli
why do aminoglycosides need O2 to take effect in the 30s ribosome of bacteria?
because O2 is needed for transport across the inner membrane of bacteria (therefore, bacteria must be aerobes)
what bacteria are resistant to aminoglycosides?
anaerobic bacteria and gram + bacteria
why cant gram + bacteria be targeted only with aminoglycosides?
what is the work around?
because the cell wall is too thick
this is why aminoglycosides are used with ß-lactam or vancomycin drug (cell wall synthesis inhibitor)
streptomycin is used against what bacteria?
tuberculosis
what activity do tetracyclines have?
bacteriostatic activity
how do tetracyclines work?
they will bind to the 30s subunit blocking +RNA from entering the acceptor site
What are the tetracyclines?
tetracycline
doxycycline
minocycline
demeclocycline
how do tetracyclines work?
(STOPS PROTEIN SYNTH.)
- it prevents addition of amino acids to growing peptides
- blocks aminoacyl t-RNA from binding to mRNA-30s ribosome complex*
what will demeclocyclin affect in the body?
it will make renal tubules resistant to ADH action
for what disease can demeclocycline be used?
to treat small cell carcinoma of the lung
how is the spectrum for tetracyclines?
broad
tetracyclines will attack what kind of bacteria?
atypical
gram positive and negative, as well as anaerobes
give an example of atypical bacteria
Rickettsia
Chlamydea
Mycoplasma
what are some side effects that happen with tetracyclines?
- photosensitivity
- yellowish-brown discoloration of teeth: because they bind to calcium (not given to children or pregnant)
- skeletal deformity and frowth retardation
(not given to children (14< or pregnant)
what is the mechanism of resistance used by bacteria for tetracyclines?
- development of efflux pump (encoded by plasmids)
• antibacterial goes into the bacteria and by using the pump, it pumps it back out
what atypical bacteria will be targeted by tetracyclines?
Ricketsia
Chlamydia
Mycoplasma
how is the spectrum for chloramphenicol?
broad
what will chlorampenicol do?
it will bind to the 50s subunit of bacterial ribosome and blocks peptidyl transferase action (no synthesis of new peptide bonds)
what are the side effects that come from chloramphenicol?
bone marrow suppression
aplastic anemia
In pregnancy = gray baby syndrome (cyanosis, vomiting, shock)
why is chloramphenicol not used so frequently?
it is highly toxic
how do macrolides work?
bind to 23s of the 50s of bacterial ribosomes and block protein synthase as well as translocation
for what are macrolides used?
- URTI (upper resp. tract infection)
- Treatment of community-acquired Atypical pneumonia:(Legionella, Chlamydia pneumoniae, Mycoplasma**)
- In patients allergic to penicillins
what are 3 examples of macrolide drugs?
erythromycin
azitrhomycin
clarithromycin
what is the clue to detecting a macrolide antibiotic?
they all end with -thromycin
what is the mechanism for resistance used by bacteria towards macrolides?
mehtylation of the 23s subunit in ribosome
how do linezolid work?
by binding to 50s subunit in bacterial ribosome
when is linezolid used?
to treat VRE, MRSA, MRSE, penicillin-resistant pneumococci
what are the side effects of linezolid?
thrombocytopenia
neutropenia
what is the antibiotic spectrum of linezolid?
it is narrow
what bacteria does linezolid target?
give 3 examples
gram + bacteria
Staphylococci, Streptococci, Enterococci
what is clindamycin mechanism of action?
Blocks peptide transfer (translocation) at 50s ribosomal subunit *
when is clindamycin used?
Mainly Gram-negative Anaerobes ** (eg. Bacteroides fragilis)
what is an important side-effect that occurs with Clindamycin?
Pseudomembranous colitis**
how do you detect Pseudomembranous colitis?
Watery diarrhea, abdominal pain
Also known as “Antibiotic-associated diarrhea”
why does pseudomembranous colitis occur?
Occurs when GI tract flora is suppressed allowing overgrowth of Clostridium difficile
how do streptogramins work?
they inhibit tRNA synthase
when is streptogramins used?
VRSA
VRE
what is an example of a streptogramin?
Quinupristin-Dalfopristin in combination
