Antimicrobials 1 Flashcards
In terms of chemotherapeutic index, is a higher or lower number better?
Higher
How do you calculate chemotherapeutic index?
Therapeutic dose
What is the term that refers to the property of antimicrobials causing more harm to pathogens than the host?
Selective toxicity
2 methods of action of antimicrobials generally?
Bacteriostatic
Bactericidal
What are 3 potential adverse of effects of antimicrobial therapy?
Allergic reaction
Toxic or side effects
Suppression of normal flora
2 infections that can arise as a result of the suppression of normal flora by antimicrobial therapy?
C Diff pseudomembranous colitis
Candida
How do B lactams work?
Inhibition of cell wall synthesis - B lactam ring competitively and irreversibly inhibits the cross-linking between peptidoglycan strands in the bacterial cell wall
What type of bacteria are classified by having a cell wall and are therefore particularly susceptible to B lactams?
Gram positive bacteria
What bacterial enzymes convey resistance to B lactam antibiotics?
B lactamase
What are 2 examples of aminopenicillins?
Amoxicillin
Ampicillin
Why do ampicillin and amoxicillin work against both gram positive and gram negative bacteria?
Gram positive because B lactam
Gram negative because very hydrophilic so can diffuse into cells
What is the more common name for penicillin G and by what method must it be administered?
Benzylpenicillin
IV
What is the more common name for penicillin V and by what method can it be administered?
Phenoxymethylpenicillin
Oral
What is special about flucloxacillin?
It has a structure which inhibits B lactamase activity and is therefore useful against penicillinase producing staphylococci
What is co-amoxyclav and why/how does it work?
Amoxicillin + clavulamic acid aka augmentin
Clavulamic acid inhibits most B lactamases
What are the main indications for co-amoxyclav?
Respiratory infection and UTIs by organisms which are proven to be resistant to amoxicillin
4 examples of antimicrobials which work by inhibiting cell wall synthesis?
Penicillins
Cephalosporins
Vancomycin
Teicoplanin
2 examples of first gen cephalosporin?
Cefadroxil
Cephalexin
Example of second gen cephalosporin?
Cefuroxime
3 examples of third gen cephalosporins?
Cefotaxime
Ceftazadime
Ceftriaxone
Moving through the generations, what is the pattern of efficacy?
First and second - gram positives
Third - less gram positive, more gram negative
What other advantage do third gen cephalosporins have over first and second gen ones?
More stable vs B lactamases
Example of a fourth gen cephalosporin?
Cefepime
Example of a fifth gen/advanced gen cephalosporin?
Ceftaroline
What is the most exciting use of fifth gen cephalosporin ceftaroline?
Anti-MRSA
Uses of vancomycin?
IV for septicaemia
MRSA-induced endocarditis
Pseudomembranous colitis caused by C Diff
What 2 drugs can be used for pseudomembranous colitis caused by C Diff?
Vancomycin
Teicoplanin
How do vancomycin and teicoplanin work?
By inhibiting peptidoglycan formation rather than cross linking
What is tazocin made up of?
Tazobactam (a B lactamase inhibitor) and piperacillin
What is isoniazid?
A cell wall formation inhibitor used first line for TB prevention and treatment
4 broad examples of protein synthesis inhibitors?
Aminoglycosides
Macrolides
Tetracyclines
Chloramphenicol
2 examples of aminoglycosides?
Gentamycin and streptomycin
How do aminoglycosides work?
Bind to the 30S ribosome subunit, blocking initiation of translation
Which bacteria are susceptible to aminoglycosides?
Mostly gram negatives but some gram positives
What are the 3 main risks of aminoglycoside use?
Ototoxicity via CN8 damage
Kidney damage
Narrow therapeutic index
How do macrolides work? 3 examples?
Bind to 50S subunit (halting protein synthesis)
Clarithromycin, erythromycin, azithromycin
What type of bacteria are macrolides good against?
Gram negatives
What side effects can erythromycin have?
Nausea and vomiting
What is good about azithromycin?
Very long half life so one dose works for a week e.g. For chlamydial urethritis
What spectrum do terracyclines and chloramphenicol have?
Broad spectrum
What side effect can tetracyclines have on young kids?
Discoloured teeth
What are the major risk factors of chloramphenicol?
Bone marrow aplasia
Encephalopathy
Optic neuritis
What effect can chloramphenicol have on neonates?
Grey baby syndrome
What is chloramphenicol first line for?
Nothing
Apart from topical use for bacterial conjunctivitis
4 examples of nucleic acid synthesis inhibitors?
Sulphonamides
Quinolones
5-Nitroimidazoles
Rifampicin
Examples of sulphonamides? How do they work?
Folic acid synthesis inhibitors
Trimethoprim and co-trimoxazole (sulfamethoxazole)
How do quinolones work? 2 examples?
GABA antagonists
Ciprofloxacin
Nalidixic acid
2 examples of 5-nitroimidazoles?
Metronidazole
Tinidazole
How does polymixin B work?
Binds to plasma membrane of gram negative bacteria, altering permeability and leading to leakage of contents
What method of delivery is used for polymixin B and why?
Topical, because it can work on eukaryotic cells as well
What is the fifth method of antimicrobial action?
Inhibition of synthesis of essential metabolites
What is trimethoprim an example of?
Sulfonamide
What is ciprofloxacin an example of?
Fluoroquinolone
What are the carbapenems examples of?
B lactams
What are vancomycin and teicoplanin examples of? What is their clinical significance?
Glycopeptide - good vs MRSA
What are gentamicin and streptomycin? How do they work?
Aminoglycosides - inhibition of protein synthesis
Common carbapenem used in nec fasc infection? With what?
Meropenem (+ clindamycin)
What is clindamycin?
A protein synthesis inhibitor
3 examples of tetracyclines?
Tetracycline
Doxycycline
Tigecycline
