Antimicrobials Flashcards
Which 4 drug groups belong to the class of beta lactams?
Penicillins
Cephalosporins
Carbapenems
Monobactam
Are drugs that target the cell wall bactericidal or bacteriostatic?
Bactericidal
Name drug groups that target the cell wall?
Penicillins
Cephalosporins
Carbapenems
Monobactam
Glycopeptides
Fosfomycin
Bacitracin
How do beta-lactams work?
Beta lactams bind to PBP (protein binding penicillin), a transpeptidase
PBP inhibited from cross-linking the pentapeptides = instability
Activation of autolytic pathways to cleave crosslinking
Water leaks in = cell death
Which drug class would cause a rash in somebody with glandular fever?
Penicillins
Notably ampicillin and amoxicillin
Which beta-lactams are not sensitive to beta-lactamases?
Carbapenems
Monobactams
Co-amoxiclav
Tazocin
What are 4 mechanisms of resistance against beta-lactams
Hyperproduction of existing PBP (induce saturation of abx)
Mutation of PBP to produce a new PBP with a different active site
Production of beta-lactamases to inactivate beta-lactams
What are 2 beta-lactamase inhibitors?
Clavulanic avid
(added to amoxicillin = co-amoxiclav)
(added to ticarcillin = timentin)
Tazobactam
(added to piperacillin = tazocin)
What is a notable side effect of carbapenems?
Reduces seizure threshold
What are side effects of vancomycin?
Nephrotoxic
Ototoxic
Red man syndrome
Neutropenia
Hypotension
Steven-Johnson Syndrome
What other drugs should not be given in a severe penicillin allergy?
Cephalosporins
Carbapenems
How do glycopeptides destroy the cell wall?
Binds to 2-d-alanine in the pentapeptide
This blocks the formation of cross-linking between the amino acids and peptide bonds between the peptidoglycan chains
How does fosfomycin destroy the cell wall?
Irrevseribly inhibits an enzyme that is required in the first step of cell wall synthesis
How does bacitracin destroy the cell wall?
Prevents dephosphorylation of transport proteins which inhibits cell wall synthesis
How did MRSA come about?
Mutation in cell wall genes of bacteria = new PBP produced - different active site - penicillins no longer fit in the target
What are 2 enzymes beta-lactamases can produce?
ESBL
CPE
How do bacteria mediate resistance against glycopeptides?
Mediated by transposons = alterations in peptide chains = reduced affinity to glycopeptides
Which penicillin has activity against pseudomonas?
Piperacillin
(+Tazobactam = tazocin)
What is vancomycin against?
MRSA
C.diff
Gram + -> staph, strep, bacillus
How do polymyxins work and what is it active against?
Active against gram negative bacteria - outer membrane
Bind to LPS in the membrane - act as a detergent to disrupt the membrane = cellular permeability and demise
What antibiotics are used against the cell membrane and are they bactericidal or static?
Polymyxins - gram negative
Daptomycin - gram positive
Bactericidal
How does daptomycin disrupt the cell membrane and what is it active against?
Combines with calcium to form complex
Complex inserts in to cell membrane
Forms pore like structures
Allows potassium to leak out = cell death
Active against gram positive - inner membrane
Which drugs work against the cell membranes?
Polymyxins
Daptomycin
How does polymyxin work?
Binds to LPS in the membrane acting as a detergent to cause structural changes = cellular permeability
What is polymyxin active against?
Gram negative - outer membrane
What is daptomycin active against?
Gram positive - inner membrane
How does daptomycin work?
Forms complex with calcium which facilitates the insertion into cell membrane - pore like structures in the membrane - potassium leaks out = cell death
What is a side effect of daptomycin?
Skeletal muscle toxicity - rhabdomyolysis
Which drugs inhibit enzymes in the folate synthesis pathway?
Sulphonamides
Trimethoprim
Reduced production of purines and pyrimidines - reduce growth - bacteriostatic
What are side effects of fluoroquinoloes?
Tendon damage or rupture
Reduce seizure threshold
Aortic aneurysm and dissection
What is the action of fluoroquinolones?
Stimulate the cutting part of DNA gyrase(relaxes the supercoil) but inhibits the ligase domain that repairs it together
What is the action of metronidazole and nitrofurantoin?
Bind to nitroreductase which produces active metabolites of the drug and free radicals - this damages helical structure of DNA, RNA, the cell = cell death
Which antibiotics work against the 50S subunit of ribosomes?
Macrolides
Chloramphenicol
Bacteriostatic
Which antibiotics work against the 30S subunit of ribosomes?
Aminoglycosides
Tetracyclines
Are aminoglycosides bacteriostatic or cidal?
Bactericidal
Are tetracyclines bacteriostatic or cidal?
bacteriostatic
Which abx are nephrotoxic and ototoxic?
Aminoglycosides
Vancomycin
What are side effects of tetracyclines?
Photosensitivity
GI disturbance
Discolouration of teeth and bone deformation (high affinity for calcium so accumulate in the bone)
What are side effects of chloramphenicol?
Grey baby syndrome
Aplastic anaemia
What are side effects of macrolides?
QT prolongation
Cholestatic hepatitis
Eosinophilia
Rash
GI dysfunction
Which abx can affect QT prolongation?
Macrolides
Fluoroquinolones
Which abx can give a false Coombs test?
Penicillin
Cephalosporin
Which abx can cause haemolytic anaemia in those with G6PD deficiency?
Nitrofurantoin
Fluoroquinolones
Which abx should be avoided in pregnancy?
Fluoroquinolones
Sulphonamides
Tetracycles
Trimethoprim
Chloramphenicol
Which abx after bactericidal?
Beta Lactams
Aminoglycosides
Glycopeptides
Polymyxin
Daptomycin
Fluoroquinolones
Nitrofurantoin
Metronidazole
Which abx after bacteriostatic?
Chloramphenicol
Macrolides
Sulphonamides
Tetracyclines
Trimethoprim
Which abx can cross the BBB?
IV ceftriaxone
IV vancomycin
IV meropenem
IV Penicillin G
Which abx are used in respiratory?
Clarithromycin
Levofloxacin
Amoxicillin
Vancomycin
Ceftriaxone
Tazocin
Co-trimoxazole
What bacteria dominates skin?
Gram positive
Staph, strep
Which bacteria dominates UTIs?
Gram negative
E coli
Which bacteria dominates intra-abdominal infections?
Gram negative
E.coli
Which drug is used to fight against pseudomonas and neutropenic sepsis?
Tazocin
What abx is used against MRSA
Glycopeptides - teicoplanin or vancomycin
Which abx target ribosomes to disrupt protein synthesis?
Tetracyclines
Aminoglycosides
Chloramphenicol
Macrolides
Examples of gram positive aerobic bacilli…
Listeria
Bacillus
Examples of gram positive anaerobic bacilli…
Clostridium
Examples of gram positive cocci …
Staph
Strep
Examples of gram negative bacilli…
Pseudomonas
Shigella
Salmonella
E.coli
Klebsiella
Enterobacter
Haemophilus
Examples of gram negative cocci…
Neisseria - gonorrhoeae/meningitidis
Moraxella
