Antibiotics Flashcards
What are the antibiotics that work by cell wall synthesis inhibition?
Beta-lactams - penicillins - cephalosporins - carbapenums - monobactams Glycopeptides - vancomycin - teicoplanin
What antibiotics act by inhibiting protein synthesis through the 30s ribosomal sub unit?
Amino glycosides
Tetracyclines
What antibiotics act by inhibiting the 50s ribosomal sub-unit?
Chloramphenicol
Clindamycin
Macrolides
Fusidic acid
What antibiotics act by blocking folic acid synthesis?
Trimethoprim
Sulphonamides
What antibiotics act by inhibiting nuclei acid synthesis by DNA gyrase inhibition?
Fluroquinolones
- cirofloxacin, norfloxacin
What antibiotics inhibit nucleoside acid synthesis through RNA polymerase inhibition?
Rifamycin
- rifampicin
What are inhibitors of cell membrane function?
Colistin
Polyene anti fungal drugs
- amphotericin B, nystatin
What are the four mechanisms of antibiotic resistance?
- Antibiotic inactivation through inactivating enzymes
- Alteration AF antibiotic target sites
- Decreased antibiotic permeability of the cell wall preventing drug access to target
- Active antibiotic eflux from bacteria
What are some examples of inactivating enzymes?
B-lactamases
Amino glycoside modifying enzymes
What are some inhibitors of beta-lactamases?
Clavulanic acid
Tazobactam
Sulbactam
What are the antibiotics that exhibit inducible chromosomal mediated beta-lactamase production?
Enterobacter Serratia Citrobacter Acinetobacter Pseudomonas Proteus vulgaris Morganella morganii
What are the two main types of b-lactamase?
ESBL - extended spectrum B lactamases which have enzymes encoded by a plasmid which can be passed between bacteria
Inducible chromosomal mediated b lactamase production from escappm
What are the usual organisms that harbour ESBLs?
E.coli
Klebsiella pneumoniae
What antibiotics do ESBLs inactivate?
All cephalosporins
What antibiotics do the ESCAPPM group inactivate?
3rd generation cephalosporins
What is the mechanism of resistance of MRSA?
Alteration in penicillin binding proteins (PBP target site) meaning methicillin cannot bind and act on the bacteria
What is the concern with use of Rifampicin alone?
Rapid development of resistance due to single step mutations that reduce the affinity of rifampicin for the RNA polymerase
What is the difference in cell wall structure between gram positive and gram negatives?
Gram positive
- simple cell wall structure that drugs can easily penetrate
Gram negative
- more complex cell envelope that requires drugs to travel through porins
What are some examples of penicillin/b-lactamase inhibitor combinations?
Amoxicillin + clavulanate
Ticarcillin + clavulanate
Piperacillin + tazobactam (tazocin)
What are some examples of first generation cephalosporins?
Cephazolin
Cephalexin
Cephalothin
What are some second generation cephalosporins?
Cefaclor
Cefuroxime
What are some third generation cephalosporins?
Cefotaxime
Ceftriaxone
Ceftazidime
What is a fourth generation cephalosporin?
Cefepime
What carbapenem does not have action against pseudomonas?
Ertapenem
What is the mechanism of Vancomycin resistance in enterococci?
Van A, B and C genetic mutations which prevent binding of vancomycin to cell wall components
What is are some differences between Van A , B and C?
A - also resistant to Teicoplanin (another glycopeptide), can be transferred between strains
B - transferred between strains
C - not able to be transferred between strains
Types of enterococcus and resistance?
All enterococci are instrinsically resistant to cephalosporins
Faecium = more resistant Faecalis = less resistant
Faecium is often resistant to amoxicillin and occasionally to Vancomycin
Faecalis is usually sensitive to amoxicillin
What drugs work via time above MIC?
B-lactams
Clindamycin
Macrolides
Linezolid
What drugs work via peak concentration above MIC?
Aminoglycasides - ie gentamicin
What drugs work as a AUC dependant killing?
Vancomycin
Fluroquinolones
What are examples of carbapenemases?
New Dehli metalloproteinase
Klebsiella pneumoniae carbapenemase
What are carbapenemases resistant to and how do you treat them?
Resistant to all B lactams
Treat with Colistin
What is a risk factor for development of Vancomycin resistant enterococci?
Use of anerobic cover - ie metronidazole
VRE genes are initally in anaerobes which are then killed and the enterococci takes up the genes and becomes VR
What drugs provide anaerobic cover?
Metronidazole Augmentin/Tazocin (B-lactamases) Clindamycin Meropenum Chloramphenicol
