MICRO: Antimicrobials Flashcards
Name 2 types of bonds in bacterial cell walls which give rigidity and protect from lysis.
Glycosidic bonds
Peptide bond
These are formed between NAM and NAG.
What are transpeptidases?
Penicillin binding proteins = involved in terminal stages of cell wall synthesis
What is the MOA of beta lactams?(2)
Inhibit transpeptidases
Structural analogues of the enzyme substrate needed
–> bactericidal
What is the MOA of glycopeptides?
Stop transpeptidase binding so it cannot form peptide bonds
Stop transglycosidase so no glycosidic bonds form
–> slowly bactericidal
What is the MOA of aminoglyosides?(2)
At 30s to prevent ELONGATION of polypeptide chain
At mRNA to cause MISREADING of codons
What is the MOA of tetracyclines?
At 30s they reversibly bind and prevent tRNA binding to ACCEPTOR site, inhibiting protein synthesis.
–> bacteriostatic
What is the MOA of macrolides?(2)
At 50s they bind and stop TRANSLATION
They also stimulate DISSOCIATION of tRNA so inhibit protein synthesis
What is the MOA of chloramphenicol?
At 50s it binds to peptidyl transferase to inhibit formation of PEPTIDE BONDS during translation
What is the MOA of oxazolidinones?
At 23s of 50s subunit to prevent formation of 70s INITIATION COMPLEX (required for translation)
What is the MOA of quinolones?
Act at alpha-subunit of DNA gyrase
–> bactericidal
What is the MOA of nitromidazole? (e.g. metronidazole)
–>rapidly bactericidal
Produce an active intermediate in anaerobic conditions which causes DNA strand breakage
What is the MOA of rifamycins?
Bind RNA polymerase which inhibits initiation of protein synthesis
–> bactericidal
What is the MOA of daptomycin?
Cyclic lipopetide
What is the MOA of colistin?
Polymyxin that destroys the outer cell membrane of gram -ve organisms
What is the MOA of sulfonamides/ diaminopyrimidines?
Interfere with folic acid metabolism –> acts on DNA
What is the use of tazobactam in tazocin?
Prevents BL breakdown of piperacillin
Which penicillin combo can be used for E coli?
Co-amoxiclav a.k.a. augmentin
Which penicillin is stable to BL?
Flucloxacillin
Which penicillin is used for HAI and pseudomonas?
Piperacillin
Which penicillins are broken down by BLs?
Penicillin, Amoxicillin, Piperacillin
Name a first, second, third gen cephalosporin. What is the trend?
CePHALexin - 1st
CeFURoxime -2nd
CefoTAXime - 3rd
Increasing activity against gram -ve bacilli
Which cephalosporin is assoc with C diff?
Ceftriaxone
Which cephalosporin is similar to amox but stable against BL?
CeFURoxime - but less stable against anaerobes
Which cephalosporin is good for pseudomonas?
CefTAZidime
What are the only beta lactam group stable to ESBLs?
Carbapenems
What is an advantage of carbapenems?
Very broad spectrum
What is a disadvantage of carbapenems ?
Klebsiella/Acinetobacter resistance
Why are beta lactams used in meningitis?
Cross BBB when inflammed
How are beta lactams excreted?
Renally
Which organisms are glycopeptides used for?
Gram +ve (can’t penetrate wall of gram -ves)
Name 2 uses of glycopeptides.
MRSA and C diff
What is the C in MLSCOAT of antibiotics which inhibit DNA?
Chloramphenicol
Which group is clindamycin?
Lincosamines
Which group is gentamicin?
Aminoglycoside
Which group is erythromycin?
Macrolide
What are 2 complications of aminoglycosides?
Nephrotoxicity and ototoxicity
What is a disadvantage of aminoglycosides?
Not good for abscesses as they are inactivated at low pH
Gentamicin not active against anaerobes
Which MLSCOAT are good for pseudomonas?
Gentamicin/tobramycin (aminoglycosides)
Which MLSCOAT are good for intracellular pathogens?
Tetracyclines (chlamydia, rickettsiae, mycoplasma)
Which MLSCOAT is active against MDR?
Tigecycline
What is a complication of tetracyclines?
Deposit in bone and discolour teeth . May also cause light sensitive rash
List 2 uses of macrolides.
Staph/strep in pen allergic
Atypical pneumonia e.g. legionella, mycoplasma
What are macrolides not effective against ?
Minimal activity against gram -ve (although newer ones like azithromycin can be used for Salmonella/bronchiectasis in CF)
Why are macrolides and penicillins combined e.g. in strep pyogenes?
Stationary phase will not be affected by beta lactams alone but macrolides will stop toxin production here
What are 2 complications of chloramphenicol?
Aplastic anaemia
Grey baby syndrome
What is a specific use of chloramphenicol?
Pen allergic meningitis or CAP
What are 2 infections which can be treated with oxazolidinones?
VRE
MRSA
(not gram -ves)
What are 2 complications of oxazolidinones?
Thrombocytopenia
Optic neuritis
What class if ciprofloxacin?
Fluoroquinolone
Name 3 fluoroquinolones in order of gram +ve –> gram -ve activity.
Moxi
Levo
Cipro
-floxacin
Which fluoroquinolone can be used for pseudomonas?
Ciprofloxacin - fluoroquinolones have broad activity
What are 2 complications of fluoroquinolones?
Tendonitis
C diff
Name a nitromidazole used for UTI.
Nitrofurantoin
What organisms do nitromidazoles act against?
Anaerobic bacteria
Protozoa
Which antimicrobials inhibit RNA synthesis?
Rifamycins
What is a disadvantage of rifamycins?
Resistance (altered target single aa) develops quickly so never use alone
Apart from TB, what other conditions is rifamycin used to treat?
Prosthetic joint
Endocarditis
(disrupts biofilms)
Is daptomycin only against gram +ve or -ve?
GRAM +VE ONLY e.g. MRSA, VRE
Is colistin used against gram +ve or -ve? Name 3 organisms.
Gram -ve e.g. pseudomonas, acinetobacter, klebsiella
Name 2 inhibitors of folate metabolism.
Sulfonamide
Diaminopyrimidines (trimethoprim - but 40% E coli are resistant)
Name a combination use of a sulfonamide.
Sulphamethoxazole + trimethoprim = CO-TRIMOXAZOLE
What is good about sulfonamides?
Very broad spectrum
